Neurotensin, Antipsychotic Drugs, and Schizophrenia Basic and Clinical Studies CHARLES B. NEMEROFF,Osb BETH LEVANT,C BECKY MYERS,b AND GARTH BISSETTEd Department of Psychiatry and Behavioral Sciences Emory University School of Medicine Atlanta, Georgia 30322 Dupont Merck Pharmaceutical Company Wilmington, Delaware 19898 dDepartment of Psychiatry Duke University Medical Center Durham. North Carolina 27710 Almost immediately after elucidation of the structure of neurotensin (NT), it was quickly reported that the peptide produced marked physiological alterations after direct administration into the central nervous system (CNS); these effects differed substantially from those observed after peripheral administration of the peptide. These early studies have been reviewed.1V2What was most striking about these early observations was the remarkable similarity between the effects of centrally administered NT and systemically administered antipsychotic drugs such as chlorpromazine or haloperidol. Thus NT, like neuroleptics, potentiated barbiturate- and ethanol-induced narcosis,3 inhibited avoidance but not escape responding in a discrete trial-conditioned avoidance ~ a r a d i g mblocked ,~ the locomotor hyperactivity induced by psychostimulants including methylphenidate, cocaine, and d-am~hetamine,~ and inhibited rates of intracranial electrical self-stimulation.6 Similarities in the neurochemical effects of centrally administered NT and antipsychotic drugs have also been reported, including increases in dopamine (DA) turnover, as assessed by several different methods.’ Closer scrutiny of the behavioral data revealed even closer similarities of centrally administered NT and atypical antipsychotic drugs. For example, direct injection of NT into the nucleus accumbens, a major terminal site of the mesolimbic DA system attenuates damphetamine-induced hyperactivity, whereas direct injection of NT into the nucleus caudatus, a major terminal site of the nigroneostriatal DA system does not attenuate d-amphetamine-induced stereotypic behavior. This finding suggested that NT might selectively modulate mesolimbicortical DA neurons while exerting few if any effects on the nigroneostriatal DA system-a profile desirable in drug development because
(1 Address for correspondence: Charles B. Nemeroff, M.D., Ph.D., Department o f Psychiatry and Behavioral Sciences, Emory University School of Medicine, 1639 Pierce Drive, Box AF, Atlanta, Georgia 30322.
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of the presumed absence of both extrapyramidal side effect and tardive dyskinesia liability. In this monograph we review in detail work conducted in our laboratory on (1) the effects of antipsychotic drugs on brain NT systems and (2) clinical studies in which NT has been measured in cerebrospinal fluid (CSF) of drug-free schizophrenic patients.
EFFECTS OF ANTIPSYCHOTIC DRUGS ON REGIONAL BRAIN NEUROTENSIN CONCENTRATIONS A little more than a decade ago, Govani et al. 8 reported that acute or chronic treatment with haloperidol, pimozide, chlorpromazine, and other clinically efficacious antipsychotic drugs increases NT concentrations in the nucleus accumbens and caudate nucleus. Phenothiazines without antipsychotic efficacy, including promazine and promethazine, did not produce this effect, suggesting a relationship between clinical efficacy and increases in NT concentration in these two major DA terminal regions. No effects of antipsychotic drug treatment on NT concentrations in several other brain
-.- Ep 560
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FIGURE 1. Effect of the chronic administration of haloperidol, clozapine, or the drug vehicle on the concentration of neurotensin-like immunoreactivity in selected brain nuclei or areas. Values are means k SEM;n = number shown at the bottom of each column. * p < 0.05 compared to vehicleinjected controls. (From Kilts et al.9 with permission from Biochemical Pharmacology.)
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FIGURE 2. The effect of (+) butaclamol, haloperidol, and haloperidol with d-amphetamine on NT
content of the anterior caudate nucleus. Compared to vehicle-treatedcontrols, haloperidol ( p < 0.01). (+) butaclamol ( p < 0.05), and haloperidol plus amphetamine ( p < 0.05) significantly increased NT levels. (-) Butaclamol and amphetamine alone were without effect. * p < 0.05, ** p < 0.01. (From Bissette ez al. with permission from Neuropsychophamcology.)
areas were observed including the hypothalamus, amygdala, and cortex. Our group has confirmed and extended these seminal observations in a series of studies, utilizing an antiserum that recognizes the midportion of the NT molecule. In our first comprehensive study? NT concentrations were measured in 38 microdissected rat brain nuclei dissected by the method of PalkovitsIo after chronic (14-day) treatment with either haloperidol, a typical butyrophenone antipsychotic, or clozapine, an atypical antipsychotic. The concentration of NT was markedly elevated in the nucleus accumbens after treatment with either drug, but the caudate NT concentration was increased only in the haloperidol-treated rats (FIG. 1). This finding suggested that the clinical efficacy of antipsychotic drugs may be predicted by the increase in NT concentration in the nucleus accumbens while the extrapyramidal side effect liability may be predicted by alterations in NT concentrations in the caudate nucleus. Also of interest was the finding that both haloperidol and clozapine reduced the concentration of NT in the medial prefrontal cortex and the bed nucleus of the stria terminalis. To begin to elucidate the neurochemical mechanisms and structure-activity relations associated with the antipsychotic drug-induced increase in NT concentrations, we measured regional brain NT concentrations after chronic (21-day) treatment with (+) butaclamol and (-) butaclamol." The (-) isomer of butaclamol has virtually all of the pharmacological properties of the (+) isomer but does not act as a DA Dz receptor antagonist. The (+) isomer, but not the (-) isomer, increased NT concen-
NEhEROFF et af.: SCHIZOPHRENIA NUCLEUS ACCUMBENS
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FIGURE 3. Effects of chronic treatment with haloperidol, atropine, and haloperidol
+
atropine on neurotensin concentrations of the nucleus accumbens and anterior and posterior caudate. Rats (n = 10 per group) were treated with haloperidol (1 mglkg), atropine sulfate (20 mg/kg), or haloperidol + atropine (1 mg/kg; 20 mg/kg) for 21 days. ** p < 0.01, * p < 0.05 when compared to control by ANOVA and the Student-Newman-Keulsmultiple comparisons test. 7 p < 0.01 when compared to haloperidol (1 mg/kg).
trations in the nucleus accumbens and the caudate nucleus (FIG.2). These observations indicate that the effects of neuroleptic drugs at serotonin, acetylcholine, histamine, and a-adrenergic receptors likely do not mediate the increase in NT concentrations after chronic treatment. Moreover the data suggest that DA D2 receptor blockade likely plays a role in the NT increase after antipsychotic drug treatment. To determine whether the anticholinergic properties of antipsychotic drugs might mediate the increase in NT concentration after neuroleptic drug treatment, rats were treated chronically with atropine or scopolamine, and the effects on NT concentrations compared with those of haloperidol (FIG.3). The anticholinergic drugs did not increase NT concentrations in either the caudate nucleus or nucleus accumbens,l* nor did they alter the effects of haloperidol on NT concentrations. Recently we reported that neither acute nor chronic treatment with desipramine, a tricyclic antidepressant; chlordiazepoxide, an anxiolytic benzodiazepine; or diphenhydramine, a histamine H I receptor antagonist, alters the concentration of NT in any of seven brain regions studied, including the nucleus accumbens or the caudate nucleus. l 3 One important consideration is whether tolerance develops to the effects of antipsychotic drugs on regional brain NT concentrations. This is of paramount importance because there is no clinical tolerance to the therapeutic effects of these drugs, and many of the neurochemical effects first posited to underlie the clinical actions of these
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TABLE1. Effects of Long-Term (8 months) Administration of Vehicle or Haloperidol (1.3-1.5 mg/kg per day) and Effects of Withdrawal from Long Administration on the Concentrations of Neurotensin in the Rat Brain Long-Term Brain Region Cortex c-P NAS mPFC OT
SN VTA p p
Control (pdmg) 65.9 f 84.1 f 333.9 f 176.0 f 516.8 f 360.0 f 1819.9 f
8.9 14.9 27.0 13.2 37.9 18.8 59.0
n
8 7 8 7 7 7 7
Withdrawal
Haloperidol (pg/mg) 58.2 f 112.8 f 434.6 f 140.8 f 439.9 f 315.6 f 1737.3 f
4.4 5.2 22.9b 18.1 30.7 15.6 71.0
n
Control (pglmg)
10 61.9 f 9 85.3 f 10 420.6 f 10 122.5 f 10 469.3 f 10 278.1 f 9 1682.8 f
n
7.4 18.8 105.4 10.9 44.7 24.9 90.9
6 6 6 6 6 7 7
Haloperidol (pg/mg) 59.9 f 48.3 f 246.8 f 124.0 f 406.9 f 297.4 f 1663.9 f
4.2 5.1a 26.3a 8.4 36.3 30.9 77.2
n
9 9 9 9 8 9 9
< 0.05 compared to control group. < 0.022 compared to control group.
drugs show acute tachyphylaxis. We therefore measured regional brain NT concentrations in rats treated with haloperidol (in the drinking water) for three weeks or eight months. Both short-term and long-term treatment with this butyrophenone increased NT concentrations in the nucleus accumbens and caudate putamen.14 Thus no tolerance occurs to this neurochemical effect of haloperidol. Of interest was the observation that abrupt withdrawal from long-term haloperidol resulted in a decrease in NT concentrations in these two brain areas below control values (TABLE1).
T
HALoeERlDoL
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REUOXIPRIDE
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FIGURE 4. Effects of chronic treatment with haloperidol and the atypical antipsychotics sulpiride, rimcazole, and remoxipride on neurotensin concentrations in the caudate nucleus. n = 8 animals for all treatments except rimcazole (50 mg/kg) where n = 5. # p < 0.01, * p < 0.05. ANOVA and Dunnett’s test. (From Levant er d.I5with permission from Regulatory Peprides.)
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The effects of several atypical antipsychotic drugs on CNS NT systems, in addition to those of clozapine, (vide supra) have been evaluated.15 Chronic treatment with both sulpiride and rimcazole, but not remoxipride, increases caudate nucleus NT concentrations (FIG. 4). Other putative antipsychotics of novel structure have also been investigated. s(+)N-n-propylnorapomorphine,an aporphine with limbic-selective DA antagonist properties, but not the inactive R( -) enantiomer, increases NT concentrations in the nucleus accumbens, caudate nucleus, and substantia nigra after chronic (10-day) administration (FIG. 5). l6 Similarly CI-943, a novel atypical antipsychotic without appreciable affinity for DA-binding sites, produces marked increases in NT concentrations in the nucleus accumbens, caudate nucleus, hypothalamus, and substantia nigrahentral tegmental area after three weeks of treatment (FIG. 6).” Our most concerted effort in recent years has been scrutiny of the effects of the sigma receptor antagonist BMY 14802. The sigma receptor, formerly believed to be an opioid receptor subtype, may mediate the psychotomimetic effects of certain drugs of abuse, and this site has been implicated in the mechanism of action of antipsychotic drugs.18 BMY 14802 has no affinity for any DA receptor subtypes but possesses a
+I
.su) C 0
c
23
i
FIGURE 5. Effects of aporphine isomers and of haloperidol on neurotensin concentrations of microdissected regions of rat brain. Rats (mean n = 16) were injected daily i.p. for 10 days with S (+) NPA or R (-) NPA (3 mg/kg three times daily) or haloperidol (3 mg/kg per day), and NT concentrations (as mean f SEM percent of controls) are shown for regions in which significant changes were found: nucleus accumbens septi (N. ACC),nucleus caudatus (caudate), substantia nigra compacta (S. Nigra), piriform cerebral cortex (Piri CTX), and mesoprefrontal cortex (MPF CTX). An asterisk indicates differences from corresponding controls. (From Nemeroff er al. 16 with permission from Neuropsychophamcology. )
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FIGURE 6. Effects of CI-943and haloperidol on regional brain neurotensin concentrations. Rats
were injected i.p. with CI-943(40mg/kg) or haloperidol (1 mg/kg) for 23 days. * p < 0.01 compared to control; t p < 0.01 compared to haloperidol by ANWA and the Student-Newman-Keuls multiple comparisons test. (From Levant er al. with permission from Synapse.)
behavioral profile similar to that of antipsychotic drugs. Both acute and chronic BMY 14802 produce dose-dependent increases in NT concentrations in the nucleus accumbens, anterior and posterior caudate (FIG.7).19 In addition, we have recently shown that both acute and chronic treatment with BMY 14802 produce significant decreases in the NT concentration of the frontal cortex. When administered concomitantly, low doses of haloperidol and BMY 14802 produce additive increases in NT content of the nucleus accumbens and caudate. Moreover, treatment with SCH 23390, a DA DI antagonist, did not attenuate the NT increase produced by haloperidol or BMY 14802.20
Finally, in collaborationwith Merchant and Dona, we demonstrated that like haloperidol, BMY 14802 increases the expression of proNT mRNA, as measured by in situ hybridization (FIG. 8). These findings indicate that both haloperidol and BMY 14802 increase NT biosynthesis in the nucleus accumbens and dorsolateral caudate nucleus.2'
CLINICAL STUDIES WITH NEUROTENSIN In a series of clinical studies we have demonstrated that a subpopulation of drugfree schizophrenic patients exhibit low CSF concentrations of NT.22-24 After treat-
NUCLEUS ACCUMBENS ANTERIOR CAUDATE POSTERIOR CAUDATE
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BMY 14802 FIGURE 7. Dose-response effects of BMY
14802 on regional NT concentrations. Animals were
treated with BMY 14802 and sacrificed 18 hr after injection. Values represent means f SEM expressed as percentage of control; n = 7-8 animals. * * p < 0.01, * p < 0.05, by ANOVA and Dunnett's test. (From Levant and Nemeroff19 with permission from the Journal OfPhamcdogy and Experimental lherapeutics. )
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FIGURE 8, Quantification of the effects of BMY 14802 on regional levels of proneurotensin mRNA. Rats (n = 5 per group) were sacrificed 3 hr and 18 hr after treatment with BMY 14802 (35 mg/kg). Autoradiograms were quantified with a RAS-loOO image analysis system. Data is expressed as optical density (OD) X 100. * * p < 0.01, * p < 0.05 when compared to control; t t p < 0.01. t p < 0.05 when compared to 18 hr by ANOVA and the Student-Newman-Keuls multiple comparisons test.
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FIGURE 9. CSF neurotensin levels of 20 psychotic patients and six comparison subjects at baseline and of the patients in relation to drug-response patterns and DSMIII diagnosis. (From Garver et al.25 with permission from the American Journal of Psychiatv.)
ment with antipsychotic drugs, CSF NT concentrations increased in the low CSF NT subgroup. Recently we have demonstrated that in a group of 20 patients with moodincongruent psychoses largely DSM-IIIR schizophrenia, CSF NT concentrations were low in a subgroup of psychotic women whose clinical response to haloperidol was delayed 11 to 35 days.25 These patients with low CSF NT concentrations were lithium nonresponders and had greater thought disorder, delusions/hallucinations,behavioral disorganization, and impaired functioning than psychotic patients with higher CSF NT concentrations (FIG.9). The data reviewed in this chapter provides further evidence for a role for NT in the mechanism of action of antipsychotic drugs and in the pathophysiology of schizophrenia. The recent discovery of the gene sequence for the NT receptor26 will likely hasten the development of NT receptor agonists, a potentially novel class of antipsychotic drugs. REFERENCES KASCKOW, I. & C. B. NEMEROFF. 1991. The neurobiology of neurotensin: Focus on neurotensin-dopamine interactions. Regul. Peptides 36: 153-164. 2. NEMEROFF,C. B., D. LUTTINGER & A. J. PRANCE,JR. 1983. Neurotensin and bombesin. In Handbook of Psychopharmacology. L. L. Iversen & S.H.Snyder, Eds. 16: 363-466. Plenum Press. New York. 1.
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3. NEMEROFF, C. B., G. BISSETTE, A. J. PRANGE, JR., P. T. LOOSEN, T. S. BARLOW & M. A. LIPTON. 1977. Neurotensin: Central nervous system effects of a hypothalamic peptide. Brain Res. U8: 485-496. 4. LUTTINGER, D., C. B. NEMEROFF & A. J. PRANGE, JR. 1982. The effects of neuropeptides on discrete-trial conditioned avoidance responding. Brain Res. 237 183-192. 5. NEMEROFF, C. B., D. LUTTINGER, D. E. HERNANDEZ, R. B. MAILMAN, G. A. MASON,S. D. DAVIS,E. WIDERLOV, G. D. FRYE,C. D. KILTS,K. BEAUMONT, G. R. BREESE& A. I. PRANGE, JR. 1983. Interactions of neurotensin with brain dopamine systems: Biochemical and behavioral studies. J. Pharmacol. Exp. Ther. 225: 337-345. 6. LUTTINGER, D., C. B. NEMEROFF, R. A. KING,G. N. ERVIN& A. J. PRANGE,JR. 1981. The effect of injection of neurotensin into the nucleus accumbens on behaviors mediated by the mesolimbic dopamine system in the rat. In The Neurobiology of the Nucleus Accumbens. R. B. Chronister & J. F. DeFrance, Eds.: 322-332. Haer Institute for Electrophysiological Research. Bar Harbor, Maine. E., C. D. KILTS,R. B. MAILMAN, C. B. NEMEROFF, T. J. MCCOWN,A. I. PRANGE, 7. WIDERLOV, JR. & G. R. BREESE.1982. Increase in dopamine metabolites in rat brain by neurotensin. J. Pharmacol. Exp. Ther. 2 2 1 1-6. S., J. S. HONG,H. Y. T. YANG& E. COSTA.1980. Increase of neurotensin content 8. GOVANI, elicited by neuroleptics in nucleus accumbens. J. Pharmacol. Exp. Ther. 215: 413-417. G. BISSETTE,T.D. ELY& C. B. NEMEROFE1988. Differential 9. KILTS,C. D., C. M. ANDERSON, effects of antipsychotic drugs on the neurotensin concentration of discrete rat brain nuclei. Biochem. Pharmacol. 3 7 1547-1554. M. 1973. Isolated removal of hypothalamic or other brain nuclei of the rat. Brain 10. PALKOVITS, Res. 59: 449-450. 1 1 . BISSETTE, G., W. T. DAUER,C. D. KILTS,L. OCONNOR & C. B. NEMEROFF. 1988. The effect of steroisomers of butaclamol on neurotensin concentrations in discrete regions of the rat brain. Neuropsychopharrnacology 1: 329-335. B., G. BISSETTE & C. B. NEMEROFF. 1989. Effects of anticholinergic drugs on regional 12. LEVANT, brain neurotensin concentrations. Eur. J. Pharmacol. 165: 327-330. G. BISETTE & C. B. NEMEROFE 1992. Specificity of the increase in 13. MYERS,B., B. LEVANT, neurotensin concentrations after antipsychotic drug treatment. Brain Res. 575: 325-328. 14. RADKE,J. M., A. J. MACLENNAN, M. C. BEINFELD, G. BISSETTE,C. B. NEMEROFF, S. R. VINCENT & H. C. FIBIGER.1989. Effects of short- and long-term haloperidol administration and withdrawal on regional brain cholecystokinin and neurotensin concentrations in the rat. Brain Res. 480: 178-183. B., G. BISSETTE,E. WIDERLOV & C. B. NEMEROFF. 1991. Alterations in regional brain 15. LEVANT, neurotensin concentrations produced by atypical antipsychotic drugs. Regul. Peptides 32: 193-201. 16. NEMEROFF, C. B., C. D. KILTS,B. LEVANT, G. BISSETTE,A. CAMPBELL & R. J. BALDESSARINI. 1991. Effects of N-n-propylnorapomorphineisomers and haloperidol on regional concentrations of neurotensin in rat brain. Neuropsychopharmacology 4: 27-34. 1991. Effects of 17. LEVANT,B., G. BISSETTE,M. D. DAVIS,T. G. HEFFNER& C. B. NEMEROFE CI-943, a potential antipsychotic drug, and haloperidol on regional brain neurotensin concentrations. Synapse 9: 225-230. S. H. & B. L. LARGENT. 1989. Receptor mechanisms in antipsychotic drug action: 18. SNYDER, Focus on sigma receptors. J. Neuropsychiatr. Clin. Neurosci. 1: 7-15. B. & C. 9. NEMEROFF. 1990. Sigma receptor “antagonist” BMY 14802 increases neuro19. LEVANT, tensin concentrations in the rat nucleus accumbens and caudate. J. Pharmacol. Exp. Ther. 254: 330-335. 1992. Further studies on the modulations of regional brain neuroB. & C. B. NEMEROFF. 20. LEVANT, tensin concentrations by antipsychotic drugs: Focus on haloperidol and BMY 14802. J. Pharmacol. Exp. Ther. In press. B., K. M. MERCHANT, D. M. DORSA& C. B. NEMEROFE 1992. BMY 14802, a potential 21. LEVANT, antipsychotic drug, increases expression of proneurotensin mRNA in the rat striatum. Mol. Brain Res. 12: 279-284. E., L. H. LINDSTROM, G. BESEV,P. J. MANBERG, C. B. NEMEROFF, G. R. BREESE, 22. WIDERLOV, J. S. KIZER& A. J. PRANGE, JR. 1982. Subnormal CSF levels of neurotensin in a subgroup
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of schizophrenic patients: Normalization after neuroleptic treatment. Am. J. Psychiatry 0 9 : 1122-1126.
23. LINDSTROM, L. H., E. WIDERLOV, G. BISSETTE & C. B. NEMEROFE 1988. Reduced CSF neurotensin concentration in drug-free schizophrenic patients. Schizophr. Res. k 55-59. 24. NEMEROFF, C. B., G. BISSETIE,E. WDERLOV, H. H. BECKMANN, R. GERNER,P. J. MANBERG, L. LINDSTROM, A. J. PRANGE,JR. & W. GATTAZ.1989. Neurotensin-like irnmunoreactivity in cerebrospinal fluid of patients with schizophrenia, depression, anorexia nervosa-bulemia and premenstrual syndrome. J. Neuropsychiatr. Clin. Neurosci. 1 16-20. 25. GARVER, D. L., G. BISSETTE, J. K. YAO& C. B. NEMEROFE 1991. CSF neurotensin concentrations in psychoses: Relationshipto symptomsand drug response.Am. J. Psychiatry 148:484-488. 26. TANAKA, K.,M.MASU& S. NAKARISHI. 1990. StNCture and functional expressionof the cloned rat neurotensin receptor. Neuron 4: 847-854.
(1 Address for correspondence: Charles B. Nemeroff, M.D., Ph.D., Department o f Psychiatry and Behavioral Sciences, Emory University School of Medicine, 1639 Pierce Drive, Box AF, Atlanta, Georgia 30322.
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of the presumed absence of both extrapyramidal side effect and tardive dyskinesia liability. In this monograph we review in detail work conducted in our laboratory on (1) the effects of antipsychotic drugs on brain NT systems and (2) clinical studies in which NT has been measured in cerebrospinal fluid (CSF) of drug-free schizophrenic patients.
EFFECTS OF ANTIPSYCHOTIC DRUGS ON REGIONAL BRAIN NEUROTENSIN CONCENTRATIONS A little more than a decade ago, Govani et al. 8 reported that acute or chronic treatment with haloperidol, pimozide, chlorpromazine, and other clinically efficacious antipsychotic drugs increases NT concentrations in the nucleus accumbens and caudate nucleus. Phenothiazines without antipsychotic efficacy, including promazine and promethazine, did not produce this effect, suggesting a relationship between clinical efficacy and increases in NT concentration in these two major DA terminal regions. No effects of antipsychotic drug treatment on NT concentrations in several other brain
-.- Ep 560
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FIGURE 1. Effect of the chronic administration of haloperidol, clozapine, or the drug vehicle on the concentration of neurotensin-like immunoreactivity in selected brain nuclei or areas. Values are means k SEM;n = number shown at the bottom of each column. * p < 0.05 compared to vehicleinjected controls. (From Kilts et al.9 with permission from Biochemical Pharmacology.)
ANNALS NEW YORK ACADEMY OF SCIENCES
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200
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;
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(N-11)
W5EIUWL d-cIy(IETIyIyE lWDmUX%+
d3YPHETAYlNE
FIGURE 2. The effect of (+) butaclamol, haloperidol, and haloperidol with d-amphetamine on NT
content of the anterior caudate nucleus. Compared to vehicle-treatedcontrols, haloperidol ( p < 0.01). (+) butaclamol ( p < 0.05), and haloperidol plus amphetamine ( p < 0.05) significantly increased NT levels. (-) Butaclamol and amphetamine alone were without effect. * p < 0.05, ** p < 0.01. (From Bissette ez al. with permission from Neuropsychophamcology.)
areas were observed including the hypothalamus, amygdala, and cortex. Our group has confirmed and extended these seminal observations in a series of studies, utilizing an antiserum that recognizes the midportion of the NT molecule. In our first comprehensive study? NT concentrations were measured in 38 microdissected rat brain nuclei dissected by the method of PalkovitsIo after chronic (14-day) treatment with either haloperidol, a typical butyrophenone antipsychotic, or clozapine, an atypical antipsychotic. The concentration of NT was markedly elevated in the nucleus accumbens after treatment with either drug, but the caudate NT concentration was increased only in the haloperidol-treated rats (FIG. 1). This finding suggested that the clinical efficacy of antipsychotic drugs may be predicted by the increase in NT concentration in the nucleus accumbens while the extrapyramidal side effect liability may be predicted by alterations in NT concentrations in the caudate nucleus. Also of interest was the finding that both haloperidol and clozapine reduced the concentration of NT in the medial prefrontal cortex and the bed nucleus of the stria terminalis. To begin to elucidate the neurochemical mechanisms and structure-activity relations associated with the antipsychotic drug-induced increase in NT concentrations, we measured regional brain NT concentrations after chronic (21-day) treatment with (+) butaclamol and (-) butaclamol." The (-) isomer of butaclamol has virtually all of the pharmacological properties of the (+) isomer but does not act as a DA Dz receptor antagonist. The (+) isomer, but not the (-) isomer, increased NT concen-
NEhEROFF et af.: SCHIZOPHRENIA NUCLEUS ACCUMBENS
** T
**
149 ANTERIOR
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CAUDATE
CAUDATE
**
300 -.
**
T
200 -.
100
-.
0-
0C O m L
U I l HALOPERIDOL
BpB HALOPEAIDOL
+ ATROPINE
FIGURE 3. Effects of chronic treatment with haloperidol, atropine, and haloperidol
+
atropine on neurotensin concentrations of the nucleus accumbens and anterior and posterior caudate. Rats (n = 10 per group) were treated with haloperidol (1 mglkg), atropine sulfate (20 mg/kg), or haloperidol + atropine (1 mg/kg; 20 mg/kg) for 21 days. ** p < 0.01, * p < 0.05 when compared to control by ANOVA and the Student-Newman-Keulsmultiple comparisons test. 7 p < 0.01 when compared to haloperidol (1 mg/kg).
trations in the nucleus accumbens and the caudate nucleus (FIG.2). These observations indicate that the effects of neuroleptic drugs at serotonin, acetylcholine, histamine, and a-adrenergic receptors likely do not mediate the increase in NT concentrations after chronic treatment. Moreover the data suggest that DA D2 receptor blockade likely plays a role in the NT increase after antipsychotic drug treatment. To determine whether the anticholinergic properties of antipsychotic drugs might mediate the increase in NT concentration after neuroleptic drug treatment, rats were treated chronically with atropine or scopolamine, and the effects on NT concentrations compared with those of haloperidol (FIG.3). The anticholinergic drugs did not increase NT concentrations in either the caudate nucleus or nucleus accumbens,l* nor did they alter the effects of haloperidol on NT concentrations. Recently we reported that neither acute nor chronic treatment with desipramine, a tricyclic antidepressant; chlordiazepoxide, an anxiolytic benzodiazepine; or diphenhydramine, a histamine H I receptor antagonist, alters the concentration of NT in any of seven brain regions studied, including the nucleus accumbens or the caudate nucleus. l 3 One important consideration is whether tolerance develops to the effects of antipsychotic drugs on regional brain NT concentrations. This is of paramount importance because there is no clinical tolerance to the therapeutic effects of these drugs, and many of the neurochemical effects first posited to underlie the clinical actions of these
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TABLE1. Effects of Long-Term (8 months) Administration of Vehicle or Haloperidol (1.3-1.5 mg/kg per day) and Effects of Withdrawal from Long Administration on the Concentrations of Neurotensin in the Rat Brain Long-Term Brain Region Cortex c-P NAS mPFC OT
SN VTA p p
Control (pdmg) 65.9 f 84.1 f 333.9 f 176.0 f 516.8 f 360.0 f 1819.9 f
8.9 14.9 27.0 13.2 37.9 18.8 59.0
n
8 7 8 7 7 7 7
Withdrawal
Haloperidol (pg/mg) 58.2 f 112.8 f 434.6 f 140.8 f 439.9 f 315.6 f 1737.3 f
4.4 5.2 22.9b 18.1 30.7 15.6 71.0
n
Control (pglmg)
10 61.9 f 9 85.3 f 10 420.6 f 10 122.5 f 10 469.3 f 10 278.1 f 9 1682.8 f
n
7.4 18.8 105.4 10.9 44.7 24.9 90.9
6 6 6 6 6 7 7
Haloperidol (pg/mg) 59.9 f 48.3 f 246.8 f 124.0 f 406.9 f 297.4 f 1663.9 f
4.2 5.1a 26.3a 8.4 36.3 30.9 77.2
n
9 9 9 9 8 9 9
< 0.05 compared to control group. < 0.022 compared to control group.
drugs show acute tachyphylaxis. We therefore measured regional brain NT concentrations in rats treated with haloperidol (in the drinking water) for three weeks or eight months. Both short-term and long-term treatment with this butyrophenone increased NT concentrations in the nucleus accumbens and caudate putamen.14 Thus no tolerance occurs to this neurochemical effect of haloperidol. Of interest was the observation that abrupt withdrawal from long-term haloperidol resulted in a decrease in NT concentrations in these two brain areas below control values (TABLE1).
T
HALoeERlDoL
35 100 SULPHllDE
12.5 25 u) RlucAZoLE
2.5
5
REUOXIPRIDE
DOSE (mg/kg/day)
FIGURE 4. Effects of chronic treatment with haloperidol and the atypical antipsychotics sulpiride, rimcazole, and remoxipride on neurotensin concentrations in the caudate nucleus. n = 8 animals for all treatments except rimcazole (50 mg/kg) where n = 5. # p < 0.01, * p < 0.05. ANOVA and Dunnett’s test. (From Levant er d.I5with permission from Regulatory Peprides.)
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The effects of several atypical antipsychotic drugs on CNS NT systems, in addition to those of clozapine, (vide supra) have been evaluated.15 Chronic treatment with both sulpiride and rimcazole, but not remoxipride, increases caudate nucleus NT concentrations (FIG. 4). Other putative antipsychotics of novel structure have also been investigated. s(+)N-n-propylnorapomorphine,an aporphine with limbic-selective DA antagonist properties, but not the inactive R( -) enantiomer, increases NT concentrations in the nucleus accumbens, caudate nucleus, and substantia nigra after chronic (10-day) administration (FIG. 5). l6 Similarly CI-943, a novel atypical antipsychotic without appreciable affinity for DA-binding sites, produces marked increases in NT concentrations in the nucleus accumbens, caudate nucleus, hypothalamus, and substantia nigrahentral tegmental area after three weeks of treatment (FIG. 6).” Our most concerted effort in recent years has been scrutiny of the effects of the sigma receptor antagonist BMY 14802. The sigma receptor, formerly believed to be an opioid receptor subtype, may mediate the psychotomimetic effects of certain drugs of abuse, and this site has been implicated in the mechanism of action of antipsychotic drugs.18 BMY 14802 has no affinity for any DA receptor subtypes but possesses a
+I
.su) C 0
c
23
i
FIGURE 5. Effects of aporphine isomers and of haloperidol on neurotensin concentrations of microdissected regions of rat brain. Rats (mean n = 16) were injected daily i.p. for 10 days with S (+) NPA or R (-) NPA (3 mg/kg three times daily) or haloperidol (3 mg/kg per day), and NT concentrations (as mean f SEM percent of controls) are shown for regions in which significant changes were found: nucleus accumbens septi (N. ACC),nucleus caudatus (caudate), substantia nigra compacta (S. Nigra), piriform cerebral cortex (Piri CTX), and mesoprefrontal cortex (MPF CTX). An asterisk indicates differences from corresponding controls. (From Nemeroff er al. 16 with permission from Neuropsychophamcology. )
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FIGURE 6. Effects of CI-943and haloperidol on regional brain neurotensin concentrations. Rats
were injected i.p. with CI-943(40mg/kg) or haloperidol (1 mg/kg) for 23 days. * p < 0.01 compared to control; t p < 0.01 compared to haloperidol by ANWA and the Student-Newman-Keuls multiple comparisons test. (From Levant er al. with permission from Synapse.)
behavioral profile similar to that of antipsychotic drugs. Both acute and chronic BMY 14802 produce dose-dependent increases in NT concentrations in the nucleus accumbens, anterior and posterior caudate (FIG.7).19 In addition, we have recently shown that both acute and chronic treatment with BMY 14802 produce significant decreases in the NT concentration of the frontal cortex. When administered concomitantly, low doses of haloperidol and BMY 14802 produce additive increases in NT content of the nucleus accumbens and caudate. Moreover, treatment with SCH 23390, a DA DI antagonist, did not attenuate the NT increase produced by haloperidol or BMY 14802.20
Finally, in collaborationwith Merchant and Dona, we demonstrated that like haloperidol, BMY 14802 increases the expression of proNT mRNA, as measured by in situ hybridization (FIG. 8). These findings indicate that both haloperidol and BMY 14802 increase NT biosynthesis in the nucleus accumbens and dorsolateral caudate nucleus.2'
CLINICAL STUDIES WITH NEUROTENSIN In a series of clinical studies we have demonstrated that a subpopulation of drugfree schizophrenic patients exhibit low CSF concentrations of NT.22-24 After treat-
NUCLEUS ACCUMBENS ANTERIOR CAUDATE POSTERIOR CAUDATE
bb T
200 -A 0 [1L
t-
z 150--
0 0
LL
0
lo0l
50 --
S.S YC/KC
10 UC/KC
20 MC/KC
80 MC/KC
SS UC/KC
BMY 14802 FIGURE 7. Dose-response effects of BMY
14802 on regional NT concentrations. Animals were
treated with BMY 14802 and sacrificed 18 hr after injection. Values represent means f SEM expressed as percentage of control; n = 7-8 animals. * * p < 0.01, * p < 0.05, by ANOVA and Dunnett's test. (From Levant and Nemeroff19 with permission from the Journal OfPhamcdogy and Experimental lherapeutics. )
0CONTROL EZd 3h Kl 18h
** tt
-
0
.- 15
*
X
W
NUCLEUS ACCUMBENS
DORSAL CAUDATE
MEDIAL CAUDATE
VENTRAL CAUDATE
GLOBUS PALLIDUS
FIGURE 8, Quantification of the effects of BMY 14802 on regional levels of proneurotensin mRNA. Rats (n = 5 per group) were sacrificed 3 hr and 18 hr after treatment with BMY 14802 (35 mg/kg). Autoradiograms were quantified with a RAS-loOO image analysis system. Data is expressed as optical density (OD) X 100. * * p < 0.01, * p < 0.05 when compared to control; t t p < 0.01. t p < 0.05 when compared to 18 hr by ANOVA and the Student-Newman-Keuls multiple comparisons test.
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0
rn
0
0
:
rn 0
FIGURE 9. CSF neurotensin levels of 20 psychotic patients and six comparison subjects at baseline and of the patients in relation to drug-response patterns and DSMIII diagnosis. (From Garver et al.25 with permission from the American Journal of Psychiatv.)
ment with antipsychotic drugs, CSF NT concentrations increased in the low CSF NT subgroup. Recently we have demonstrated that in a group of 20 patients with moodincongruent psychoses largely DSM-IIIR schizophrenia, CSF NT concentrations were low in a subgroup of psychotic women whose clinical response to haloperidol was delayed 11 to 35 days.25 These patients with low CSF NT concentrations were lithium nonresponders and had greater thought disorder, delusions/hallucinations,behavioral disorganization, and impaired functioning than psychotic patients with higher CSF NT concentrations (FIG.9). The data reviewed in this chapter provides further evidence for a role for NT in the mechanism of action of antipsychotic drugs and in the pathophysiology of schizophrenia. The recent discovery of the gene sequence for the NT receptor26 will likely hasten the development of NT receptor agonists, a potentially novel class of antipsychotic drugs. REFERENCES KASCKOW, I. & C. B. NEMEROFF. 1991. The neurobiology of neurotensin: Focus on neurotensin-dopamine interactions. Regul. Peptides 36: 153-164. 2. NEMEROFF,C. B., D. LUTTINGER & A. J. PRANCE,JR. 1983. Neurotensin and bombesin. In Handbook of Psychopharmacology. L. L. Iversen & S.H.Snyder, Eds. 16: 363-466. Plenum Press. New York. 1.
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3. NEMEROFF, C. B., G. BISSETTE, A. J. PRANGE, JR., P. T. LOOSEN, T. S. BARLOW & M. A. LIPTON. 1977. Neurotensin: Central nervous system effects of a hypothalamic peptide. Brain Res. U8: 485-496. 4. LUTTINGER, D., C. B. NEMEROFF & A. J. PRANGE, JR. 1982. The effects of neuropeptides on discrete-trial conditioned avoidance responding. Brain Res. 237 183-192. 5. NEMEROFF, C. B., D. LUTTINGER, D. E. HERNANDEZ, R. B. MAILMAN, G. A. MASON,S. D. DAVIS,E. WIDERLOV, G. D. FRYE,C. D. KILTS,K. BEAUMONT, G. R. BREESE& A. I. PRANGE, JR. 1983. Interactions of neurotensin with brain dopamine systems: Biochemical and behavioral studies. J. Pharmacol. Exp. Ther. 225: 337-345. 6. LUTTINGER, D., C. B. NEMEROFF, R. A. KING,G. N. ERVIN& A. J. PRANGE,JR. 1981. The effect of injection of neurotensin into the nucleus accumbens on behaviors mediated by the mesolimbic dopamine system in the rat. In The Neurobiology of the Nucleus Accumbens. R. B. Chronister & J. F. DeFrance, Eds.: 322-332. Haer Institute for Electrophysiological Research. Bar Harbor, Maine. E., C. D. KILTS,R. B. MAILMAN, C. B. NEMEROFF, T. J. MCCOWN,A. I. PRANGE, 7. WIDERLOV, JR. & G. R. BREESE.1982. Increase in dopamine metabolites in rat brain by neurotensin. J. Pharmacol. Exp. Ther. 2 2 1 1-6. S., J. S. HONG,H. Y. T. YANG& E. COSTA.1980. Increase of neurotensin content 8. GOVANI, elicited by neuroleptics in nucleus accumbens. J. Pharmacol. Exp. Ther. 215: 413-417. G. BISSETTE,T.D. ELY& C. B. NEMEROFE1988. Differential 9. KILTS,C. D., C. M. ANDERSON, effects of antipsychotic drugs on the neurotensin concentration of discrete rat brain nuclei. Biochem. Pharmacol. 3 7 1547-1554. M. 1973. Isolated removal of hypothalamic or other brain nuclei of the rat. Brain 10. PALKOVITS, Res. 59: 449-450. 1 1 . BISSETTE, G., W. T. DAUER,C. D. KILTS,L. OCONNOR & C. B. NEMEROFF. 1988. The effect of steroisomers of butaclamol on neurotensin concentrations in discrete regions of the rat brain. Neuropsychopharrnacology 1: 329-335. B., G. BISSETTE & C. B. NEMEROFF. 1989. Effects of anticholinergic drugs on regional 12. LEVANT, brain neurotensin concentrations. Eur. J. Pharmacol. 165: 327-330. G. BISETTE & C. B. NEMEROFE 1992. Specificity of the increase in 13. MYERS,B., B. LEVANT, neurotensin concentrations after antipsychotic drug treatment. Brain Res. 575: 325-328. 14. RADKE,J. M., A. J. MACLENNAN, M. C. BEINFELD, G. BISSETTE,C. B. NEMEROFF, S. R. VINCENT & H. C. FIBIGER.1989. Effects of short- and long-term haloperidol administration and withdrawal on regional brain cholecystokinin and neurotensin concentrations in the rat. Brain Res. 480: 178-183. B., G. BISSETTE,E. WIDERLOV & C. B. NEMEROFF. 1991. Alterations in regional brain 15. LEVANT, neurotensin concentrations produced by atypical antipsychotic drugs. Regul. Peptides 32: 193-201. 16. NEMEROFF, C. B., C. D. KILTS,B. LEVANT, G. BISSETTE,A. CAMPBELL & R. J. BALDESSARINI. 1991. Effects of N-n-propylnorapomorphineisomers and haloperidol on regional concentrations of neurotensin in rat brain. Neuropsychopharmacology 4: 27-34. 1991. Effects of 17. LEVANT,B., G. BISSETTE,M. D. DAVIS,T. G. HEFFNER& C. B. NEMEROFE CI-943, a potential antipsychotic drug, and haloperidol on regional brain neurotensin concentrations. Synapse 9: 225-230. S. H. & B. L. LARGENT. 1989. Receptor mechanisms in antipsychotic drug action: 18. SNYDER, Focus on sigma receptors. J. Neuropsychiatr. Clin. Neurosci. 1: 7-15. B. & C. 9. NEMEROFF. 1990. Sigma receptor “antagonist” BMY 14802 increases neuro19. LEVANT, tensin concentrations in the rat nucleus accumbens and caudate. J. Pharmacol. Exp. Ther. 254: 330-335. 1992. Further studies on the modulations of regional brain neuroB. & C. B. NEMEROFF. 20. LEVANT, tensin concentrations by antipsychotic drugs: Focus on haloperidol and BMY 14802. J. Pharmacol. Exp. Ther. In press. B., K. M. MERCHANT, D. M. DORSA& C. B. NEMEROFE 1992. BMY 14802, a potential 21. LEVANT, antipsychotic drug, increases expression of proneurotensin mRNA in the rat striatum. Mol. Brain Res. 12: 279-284. E., L. H. LINDSTROM, G. BESEV,P. J. MANBERG, C. B. NEMEROFF, G. R. BREESE, 22. WIDERLOV, J. S. KIZER& A. J. PRANGE, JR. 1982. Subnormal CSF levels of neurotensin in a subgroup
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of schizophrenic patients: Normalization after neuroleptic treatment. Am. J. Psychiatry 0 9 : 1122-1126.
23. LINDSTROM, L. H., E. WIDERLOV, G. BISSETTE & C. B. NEMEROFE 1988. Reduced CSF neurotensin concentration in drug-free schizophrenic patients. Schizophr. Res. k 55-59. 24. NEMEROFF, C. B., G. BISSETIE,E. WDERLOV, H. H. BECKMANN, R. GERNER,P. J. MANBERG, L. LINDSTROM, A. J. PRANGE,JR. & W. GATTAZ.1989. Neurotensin-like irnmunoreactivity in cerebrospinal fluid of patients with schizophrenia, depression, anorexia nervosa-bulemia and premenstrual syndrome. J. Neuropsychiatr. Clin. Neurosci. 1 16-20. 25. GARVER, D. L., G. BISSETTE, J. K. YAO& C. B. NEMEROFE 1991. CSF neurotensin concentrations in psychoses: Relationshipto symptomsand drug response.Am. J. Psychiatry 148:484-488. 26. TANAKA, K.,M.MASU& S. NAKARISHI. 1990. StNCture and functional expressionof the cloned rat neurotensin receptor. Neuron 4: 847-854.
