Life Sciences, Vol. Printed in the USA
51, pp.
295-301
Pergamon
Press
E F F E C T S O F H A L O P E R I D O L A N D P R O L A C T I N S E C R E T I N G T U M O R S ON CEREBROSPINAL FLUID CONCENTRATIONS OF PROLACTIN IN T H E F E M A L E R A T
James W. Simpkins
Department of Pharmacodynamics and The Center for the Neurobiology of Aging University of Florida Gainesville, FL 32610 (Received
in final
form May 18,
1992)
Summary Studies were conducted to determine the effects of acute and chronic elewltions in prolactin (PRL) secretion on serum and cerebrospinal fluid (CSF) PRL concentrations in the female rat. Young female rats showed a dose-dependent increase in serum and CSF PRL in response to haloperidol. A time-course evaluation of serum and CSF PRL levels after haloperidol indicated that serum PRL concentrations increased markedly by 30 rain and declined thereafter; while CSF PRL increased more slowly, peaking at 2 to 8 h. In young rats with basal serum PRL levels, C S F PRL was maintained at 0.8 to 2.1% of serum PRL levels. During acute hyperprolactinemia, the CSF to serum PRL ratio increased to about 4%. During chronic severe hyperprolactinemia, induced by the growth of a MtT-W15 tumor, C S F PRL concentrations increased to 75 ng/ml, but this represented only 1.5% of serum PRL concentrations. Collectively, thse data indicate that the bloodbrain barrier effectively limits access to the brain of circulating PRL.
Prolactin (PRL) gains access to the brain and has been quantitated in hypothalamic tissue (1) as well as cerebrospinal fluid (CSF) (2-7). In addition to the well documented role of PRL in the activation of tuberoinfundibular dopamine (TIDA) neurons (see 8 for references) which are outside the blood-brain-barrier (BBB, 9), PRL has been shown to effect activity of a variety of other dopaminergic (10-14) and non-dopaminergic (13,15-18) neuronal systems which are located inside the BBB. Further, PRL alters neuronal activity in the hypothalamus (19), preoptic area and septum (20). Chronic hyperprolactinemia causes a disruption in T I D A function (16,21,22) in a manner which simulates the age-related decline in T I D A function (see 23 for refer.). As rats show an age-related hyperprolactinemia (see 23 for refer.), this endocrine condition may contribute to aging of T I D A neurons. Despite these physiologic effects of PRL on the brain, and the prospect that chronic hyperprolactinemia may contribute to damage of certain brain neuronal systems, comparitively few studies have assessed the relationship between serum and C S F PRL concentrations. In the present study we assessed the relationship between serum and C S F PRL in
Copyright
0024-3205/92 $5.00 + .00 © 1992 Pergamon Press Ltd All rights
reserved.
296
Vol.
CSF Prolactin
51, No.
4, 1992
young rats which were exposed to haloperidol-induces acute hyperprolactinemia as well as chronic hyperprolactinemia associated with the growth of a PRL-secreting tumor.
Materials and Methods Animals Sprague-Dawley female rats were purchased from Charles Rivers Laboratories (Wilmington, ]VIA) and Wistar-Furth female rats were purchased from Harlan Sprague-Dawley, Indianapolis, IN at 2 to 3 months of age. Rats were 3 to 4 months old when used in the studies. All animals were maintained in animals rooms with an artificial daily light cycle (lights on 0500-1900 h daily) and were provided food and water ad libitum.
Collection of Cerebrospinal Fluid Animals were anesthetized with dimethyl ether and a single 1 cc blood sample was obtained by cardiac puncture for later assay of serum PRL concentrations. Animals were maintained under ether anesthesia and placed in the ear bars of a David K o p f (Model 900) Steriotaxic instrument to secure the head in a position to expose the cisterna magna. Cerebrospinal fluid (CSF) was collected from a single sample by exposure of the cisterna magna through an incision made at tile base of the dorsal aspects of the skull. A 50-100 i.tl sample of C S F was slowly withdrawn. Any samples with evidence of blood in the CSF sample were discarded.
Experiment 1:
Effects of Haldol Implants on Serum and CSF Prolactin Concentrations
To induce an acute but sustained rise in serum PRL, Sprague-Dawley female rats were anesthetized with ether and implanted subcutaneously with a tablet containing 0.5 mg or 5 mg of haloperidol (Haldol®, McNeil Pharmaceuticals, Spring House, PA). Sham control rats were anesthetized, a small incision was made in the skin on the back and the wound was closed. At 4 hours after sham surgery or haloperidol dosing, serum and C S F samples were obtained for later assay of PRL concentrations. In a second study, 5 mg tablets of Haldol were implanted s.c. and serum and C S F PRL concentrations were measured at 30 min and 1, 2 and 8 hours later. In both studies, the Haldol® implant was done between 1000 and 1100 h.
Experiment 2:
Effects of M t T - W 1 5 Concentrations
Tumors
on
Serum
and
CSF
Prolactin
Female Wistar-Furth rats were implanted s.c. with minced MtT-W15 tumor tissue from a donor animal using the methods described by us previously (16,21). Three and one-half weeks later, when the tumor diameter reached approximately 2 cm, blood and CSF samples were obtained to determine serum and C S F PRL concentrations. All animals were sampled between 0900 and 1200 h.
Prolactin Radioimmunoassay Serum PRL concentrations were determined in quadruplicate (replicates at 2 serum volumes) and C S F PRL concentrations were determined from a single sample. C S F volumes used ranged from 50 to 100 p,l. The RIA used reagent kindly provided by A. F. Parlow and the National Pituitary Hormone Distribution Program of NIDDK. The reference preparation, rat PRL
Vol.
51, NO.
4, 1992
CSF P r o l a c t i n
297
RP-1 was used to quantitate hormone concentrations. The intraassay coefficient of variation ranged from 4.3 to 5.7% for the assays used in these studies.
Statistical Evaluation For comparisons involving 3 or more groups of data, one-way analysis of variance and Student-Newman Keul's tests were employed. For comparisons using two groups, Student's t tests were employed. For all comparisons a probability level of p
51, pp.
295-301
Pergamon
Press
E F F E C T S O F H A L O P E R I D O L A N D P R O L A C T I N S E C R E T I N G T U M O R S ON CEREBROSPINAL FLUID CONCENTRATIONS OF PROLACTIN IN T H E F E M A L E R A T
James W. Simpkins
Department of Pharmacodynamics and The Center for the Neurobiology of Aging University of Florida Gainesville, FL 32610 (Received
in final
form May 18,
1992)
Summary Studies were conducted to determine the effects of acute and chronic elewltions in prolactin (PRL) secretion on serum and cerebrospinal fluid (CSF) PRL concentrations in the female rat. Young female rats showed a dose-dependent increase in serum and CSF PRL in response to haloperidol. A time-course evaluation of serum and CSF PRL levels after haloperidol indicated that serum PRL concentrations increased markedly by 30 rain and declined thereafter; while CSF PRL increased more slowly, peaking at 2 to 8 h. In young rats with basal serum PRL levels, C S F PRL was maintained at 0.8 to 2.1% of serum PRL levels. During acute hyperprolactinemia, the CSF to serum PRL ratio increased to about 4%. During chronic severe hyperprolactinemia, induced by the growth of a MtT-W15 tumor, C S F PRL concentrations increased to 75 ng/ml, but this represented only 1.5% of serum PRL concentrations. Collectively, thse data indicate that the bloodbrain barrier effectively limits access to the brain of circulating PRL.
Prolactin (PRL) gains access to the brain and has been quantitated in hypothalamic tissue (1) as well as cerebrospinal fluid (CSF) (2-7). In addition to the well documented role of PRL in the activation of tuberoinfundibular dopamine (TIDA) neurons (see 8 for references) which are outside the blood-brain-barrier (BBB, 9), PRL has been shown to effect activity of a variety of other dopaminergic (10-14) and non-dopaminergic (13,15-18) neuronal systems which are located inside the BBB. Further, PRL alters neuronal activity in the hypothalamus (19), preoptic area and septum (20). Chronic hyperprolactinemia causes a disruption in T I D A function (16,21,22) in a manner which simulates the age-related decline in T I D A function (see 23 for refer.). As rats show an age-related hyperprolactinemia (see 23 for refer.), this endocrine condition may contribute to aging of T I D A neurons. Despite these physiologic effects of PRL on the brain, and the prospect that chronic hyperprolactinemia may contribute to damage of certain brain neuronal systems, comparitively few studies have assessed the relationship between serum and C S F PRL concentrations. In the present study we assessed the relationship between serum and C S F PRL in
Copyright
0024-3205/92 $5.00 + .00 © 1992 Pergamon Press Ltd All rights
reserved.
296
Vol.
CSF Prolactin
51, No.
4, 1992
young rats which were exposed to haloperidol-induces acute hyperprolactinemia as well as chronic hyperprolactinemia associated with the growth of a PRL-secreting tumor.
Materials and Methods Animals Sprague-Dawley female rats were purchased from Charles Rivers Laboratories (Wilmington, ]VIA) and Wistar-Furth female rats were purchased from Harlan Sprague-Dawley, Indianapolis, IN at 2 to 3 months of age. Rats were 3 to 4 months old when used in the studies. All animals were maintained in animals rooms with an artificial daily light cycle (lights on 0500-1900 h daily) and were provided food and water ad libitum.
Collection of Cerebrospinal Fluid Animals were anesthetized with dimethyl ether and a single 1 cc blood sample was obtained by cardiac puncture for later assay of serum PRL concentrations. Animals were maintained under ether anesthesia and placed in the ear bars of a David K o p f (Model 900) Steriotaxic instrument to secure the head in a position to expose the cisterna magna. Cerebrospinal fluid (CSF) was collected from a single sample by exposure of the cisterna magna through an incision made at tile base of the dorsal aspects of the skull. A 50-100 i.tl sample of C S F was slowly withdrawn. Any samples with evidence of blood in the CSF sample were discarded.
Experiment 1:
Effects of Haldol Implants on Serum and CSF Prolactin Concentrations
To induce an acute but sustained rise in serum PRL, Sprague-Dawley female rats were anesthetized with ether and implanted subcutaneously with a tablet containing 0.5 mg or 5 mg of haloperidol (Haldol®, McNeil Pharmaceuticals, Spring House, PA). Sham control rats were anesthetized, a small incision was made in the skin on the back and the wound was closed. At 4 hours after sham surgery or haloperidol dosing, serum and C S F samples were obtained for later assay of PRL concentrations. In a second study, 5 mg tablets of Haldol were implanted s.c. and serum and C S F PRL concentrations were measured at 30 min and 1, 2 and 8 hours later. In both studies, the Haldol® implant was done between 1000 and 1100 h.
Experiment 2:
Effects of M t T - W 1 5 Concentrations
Tumors
on
Serum
and
CSF
Prolactin
Female Wistar-Furth rats were implanted s.c. with minced MtT-W15 tumor tissue from a donor animal using the methods described by us previously (16,21). Three and one-half weeks later, when the tumor diameter reached approximately 2 cm, blood and CSF samples were obtained to determine serum and C S F PRL concentrations. All animals were sampled between 0900 and 1200 h.
Prolactin Radioimmunoassay Serum PRL concentrations were determined in quadruplicate (replicates at 2 serum volumes) and C S F PRL concentrations were determined from a single sample. C S F volumes used ranged from 50 to 100 p,l. The RIA used reagent kindly provided by A. F. Parlow and the National Pituitary Hormone Distribution Program of NIDDK. The reference preparation, rat PRL
Vol.
51, NO.
4, 1992
CSF P r o l a c t i n
297
RP-1 was used to quantitate hormone concentrations. The intraassay coefficient of variation ranged from 4.3 to 5.7% for the assays used in these studies.
Statistical Evaluation For comparisons involving 3 or more groups of data, one-way analysis of variance and Student-Newman Keul's tests were employed. For comparisons using two groups, Student's t tests were employed. For all comparisons a probability level of p
