European Journal of Pharmacology, 60 (1979) 105--108 © Elsevier/North-Holland Biomedical Press
105
Short communication ANTAGONISM BY d~I-PROPRANOLOL OF IMIPRAMINE EFFECTS IN MICE MARIO SOUTO, HENRIETTE FRANCI~S, YVES LECRUBIER, ALAIN J. PUECH and PIERRE SIMON D~partement of Pharmacologie, Facultd de Mddecine Pitid-Salpdtridre, 91, boulevard de l'HSpital, F75634 Paris Cedex 13, France
Received 2 October 1979, accepted 8 October 1979 M. SOUTO, H. FRANCI~S, Y. LECRUBIER, A.J. PUECH and P. SIMON, Antagonism by d,l-propranolol of imipramine effects in mice, European J. Pharmacol. 60 (1979) 105--108. Three agents with known or suspected antidepressant activity, imipramine, salbutamol and dexamphetamine, were active in animal tests predictive of an antidepressant effect in man: antagonism of the hypothermia induced by reserpine, by oxotremorine or by a high dose of apomorphine, and the potentiation of the yohimbine-induced toxicity. These effects were antagonized by d,l-propranolol, suggesting that the stimulation of ~-adrenergic receptors could be a common mechanism underlying their effects. These results agree with the nomdrenergic hypothesis of the pathophysiology of affective disorders. Antidepressants
Psychopharmacological tests
I. Introduction Noradrenaline (NA), dopamine (DA) and serotonin (5-HT) have been thought for many years to be involved in the neuro-regulation of m o o d . Part of the evidence for this involvement comes from the fact that standard antidepressant c o m p o u n d s (imipramine-like drugs, amphetamine, MAO inhihitors) have potent effects in pharmacological tests where NA, DA or 5-HT are directly implicated. We have shown recently that ~ d r e n e r g i c stimulants, such as isoprenaline and salbutamol, had profiles o f activity similar to those of classical antidepressant c o m p o u n d s in some pharmacological tests considered to be predictors in animals o f antidepressant activity in man (Franc~s et al., 1978) and that the effects o f isoprenaline in these tests could be antagonized b y the ~-blocker propranolol (Franc~s and Simon, 1978). Furthermore the~e already exists clinical evidence that salbutamol is active as an antidepressant in
~-Adrenergicreceptors
~-Blockers
man and t h a t its delay in the onset of therapeutic activity is shorter than that of classical antidepressants. These results are therefore consistent with the hypothesis that NA is implicated in the pathophysiology o f depressive disorders and suggest a possible role of ~-adrenergic receptors. We suggest that /3-adrenergic receptors are also involved in the pharmacological effects o f other antidepressant agents such as imipramine and amphetamine. The experiments described in the present paper were aimed to assess this possibility b y seeing whether the effects o f imipramine, d-amphetamine, and salbutamol in four different tests for antidepressant activity could be antagonized b y d,l-propranolol. Two of the tests (reserpine-induced hypothermia and potentiation of yohimbine toxicity) have confirmed predictive value whereas the other t w o (apomorphine- and oxotremorineoinduced hypothermia) have been described more recently (Puech et al., 1978).
106 2. Materials and m e t h o d s Male Swiss NMRI mice (Evic Ceba) weighing 20-22 g were used. R o o m temperature was kept at 22 -+ 1 ° C. Rectal temperature (depth 2 cm) was measured using a thermistor probe. d~l-Propranolol in aqueous solution was injected intraperitoneally (i.p.) 15 min before i.p. imipramine, amphetamine and salbutamol. For reserpine interactions, drugs were administered 4 h after i.p. reserpine (2.5 m g • kg-1). Temperature was measured at 30, 60, 90 and 120 min after the last injection. Apomorphine induced hypothermia was studied b y injecting antidepressants 30 min before apomorphine (16 m g . kg -1 s.c.). Temperature was measured 30 min after apomorphine; the animals were put individually in small boxes (4.5 × 3.5 × 11 cm). Oxotremorine-induced hypothermia was studied b y injecting antidepressants 30 rain before oxotremorine (0.5 m g • kg -1 i.p.). Temperature was measured 30, 60, 90 and 120 min after oxotremorine. The potentiation of yohimbine toxicity was studied b y injecting antidepressants 30 min before s.c. yohimbine (25 mg . k g -1) and putting the animals in groups of 10 in conventional cages (28 × 16 × 10 cm). The n u m b e r of deaths was counted at 6 0 , 1 2 0 , 1 8 0 , 2 4 0 rain and 20 h. The dose of propranolol was that with the smallest hypothermia-potentiating effect.
3. Results
The results are shown in fig. 1. Propranolol on its o w n slightly potentiated reserpineinduced h y p o t h e r m i a b u t the effect varied greatly from one occasion to another. Salbutamol, imipramine and d-amphetamine
M. SOUTO ET AL. clearly antagonized the reserpine-induced hypothermia, an antagonism which was markedly reduced b y dj-propranolol pretreatment. Similarly, there was a slight b u t consistent potentiation of b o t h apomorphineand oxotremorine-induced hypothermia b y propranolol alone whereas hypothermia induced b y either c o m p o u n d was antagonized b y salbutamol, imipramine and d-amphetamine. In b o t h tests the antagonism of apomorphine- and oxotremorine-induced hypothermia was greatly reduced by pretreatment with d,l-propranolol. Yohimbine toxicity (0 or I death in 10 mice) was n o t modified b y propranolol alone b u t was increased by salbutamol, imipramine and d-amphetamine. This increased yohimbine toxicity with the three potential antidepressants was completely antagonized b y pretreatment with d,1propranolol.
4. Discussion
The results show that propranolol can antagonize the effects of salbutamol, imipramine and amphetamine in four tests predictive of antidepressant activity in man suggesting that the pharmacological effects of these three antidepressants may in part be due to stimulation o f ~-adrenergic receptors. This conclusion requires some c o m m e n t , however, because propranolol, despite the fact that the dose used was the highest having minimal hypothermic effects, itself mildly potentiated the hypothermia induced b y reserpine, apomorphine and oxotremorine. Nevertheless propranolol's potentiation of hypothermia was not as marked or consistent as its antagonism of the effects o f salbutamol, imipramine
Fig. 1. Interaction of propranolol with salbutamol, imipramine or amphetamine on antidepressant predictive tests in mice. (a) All animals received reserpine 2.5 mg • kg -1 i.p. 5 h before temperature measurement. (b) All animals received o x o t r e m o r i n e 0.5 mg • kg -1 i.p. 60 rain before temperature measurement. (c) All animals received apom o r p h i n e 16 m g . kg -1 s.c. 30 rain before temperature measurement. (d) All animals received y o h i m b i n e 25
mg • kg -1 s.c. 4 h before death numeration, d,l-Propranolol (pro), salbutamol (salb), imipramine (imi), amphetamine (amp) were injected intraperitoneally. The injection volume was 0.25 mg/20 g. The time of administration and the doses used (mg • kg -1 ) are indicated in the figure. Each result was obtained from at least 6 mice for hypothermia, 10 mice for the toxicity of yohimbine. * P < 0.05 ; ** P < 0.01, *** P < 0.001, Student's t-test.
A N T A G O N I S M O F IMIPRAMINE B Y d,I-PROPRANOLOL (~)
107
RESERPINE
Ft~ i--
oC37.
-37°C
11.O. r-'--1
-31
.26 h-T5min.
MJ 0~
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4
0
4
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pro. 0 amp.O
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APOMORPHINE
°C38.
ID
34
30 h - 75 min. h - 60min.
t0
if'
Q
0 h- 285 rain. h-270min,
2 4
wo.O 4 0 solb.O 0 4
4 4
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108
and amphetamine in these three tests, suggesting that the antagonism observed was not simply due to the intrinsic hypothermic effect of propranolol. If stimulation of ~-adrenergic receptors is a common feature of the three antidepressants tested, is ~-adrenergic stimulation common to all antidepressants? The three drugs salbutamol, imipramine and amphetamine have different mechanisms of action -- direct receptor stimulation, blockade of monoamine reuptake and stimulation of monoamine release. MAO inhibitors increase the availability of monoamines by blocking their metabolism. Other antidepressant drugs, for example mianserin, appear to act by blocking pre-synaptic a-adrenergic receptors thereby increasing the release of NA through interruption of a negative feedback system. The hypothesis can therefore be entertained that all antidepressant drugs act through a final common mechanism of ~-adrenergic stimulation.
M. SOUTO ET AL.
If so, some dysfunction in the ~-adrenergic system would seem to be implicated in the pathophysiology of depressive illness.
References Franc~s, H., A.J. Puech and P. Simon, 1978, Profil psychopharmacologique de l'isoprdnaline et du salbutamol, J. Pharmacol. (Paris) 9, 25. Franc~s, H. and P. Simon, 1978, Isoproterenol and psychopharmacological tests: Antagonism by betaadrenergic antagonists, Pharmacol. Res. Commun. 10,211. Puech, A.J., H. Franc~s, M. Souto, R. Chermat and P. Simon, 1978, Problems of pharmacological screening for antidepressants, in: Advances in Pharmacology and Therapeutics, Vol. 5, Neuropsychopharrnacology, ed. C. Dumont (Pergamon Press, Oxford--London). Simon, P., Y. Lecrubier, R. Jouvent, A.J. Puech, J.F. Allilaire and D. WidlScher, 1978, Experimental and clinical evidences of the antidepressant effect of a beta-adrenergic stimulant, Psychol. Med. 8, 335.
105
Short communication ANTAGONISM BY d~I-PROPRANOLOL OF IMIPRAMINE EFFECTS IN MICE MARIO SOUTO, HENRIETTE FRANCI~S, YVES LECRUBIER, ALAIN J. PUECH and PIERRE SIMON D~partement of Pharmacologie, Facultd de Mddecine Pitid-Salpdtridre, 91, boulevard de l'HSpital, F75634 Paris Cedex 13, France
Received 2 October 1979, accepted 8 October 1979 M. SOUTO, H. FRANCI~S, Y. LECRUBIER, A.J. PUECH and P. SIMON, Antagonism by d,l-propranolol of imipramine effects in mice, European J. Pharmacol. 60 (1979) 105--108. Three agents with known or suspected antidepressant activity, imipramine, salbutamol and dexamphetamine, were active in animal tests predictive of an antidepressant effect in man: antagonism of the hypothermia induced by reserpine, by oxotremorine or by a high dose of apomorphine, and the potentiation of the yohimbine-induced toxicity. These effects were antagonized by d,l-propranolol, suggesting that the stimulation of ~-adrenergic receptors could be a common mechanism underlying their effects. These results agree with the nomdrenergic hypothesis of the pathophysiology of affective disorders. Antidepressants
Psychopharmacological tests
I. Introduction Noradrenaline (NA), dopamine (DA) and serotonin (5-HT) have been thought for many years to be involved in the neuro-regulation of m o o d . Part of the evidence for this involvement comes from the fact that standard antidepressant c o m p o u n d s (imipramine-like drugs, amphetamine, MAO inhihitors) have potent effects in pharmacological tests where NA, DA or 5-HT are directly implicated. We have shown recently that ~ d r e n e r g i c stimulants, such as isoprenaline and salbutamol, had profiles o f activity similar to those of classical antidepressant c o m p o u n d s in some pharmacological tests considered to be predictors in animals o f antidepressant activity in man (Franc~s et al., 1978) and that the effects o f isoprenaline in these tests could be antagonized b y the ~-blocker propranolol (Franc~s and Simon, 1978). Furthermore the~e already exists clinical evidence that salbutamol is active as an antidepressant in
~-Adrenergicreceptors
~-Blockers
man and t h a t its delay in the onset of therapeutic activity is shorter than that of classical antidepressants. These results are therefore consistent with the hypothesis that NA is implicated in the pathophysiology o f depressive disorders and suggest a possible role of ~-adrenergic receptors. We suggest that /3-adrenergic receptors are also involved in the pharmacological effects o f other antidepressant agents such as imipramine and amphetamine. The experiments described in the present paper were aimed to assess this possibility b y seeing whether the effects o f imipramine, d-amphetamine, and salbutamol in four different tests for antidepressant activity could be antagonized b y d,l-propranolol. Two of the tests (reserpine-induced hypothermia and potentiation of yohimbine toxicity) have confirmed predictive value whereas the other t w o (apomorphine- and oxotremorineoinduced hypothermia) have been described more recently (Puech et al., 1978).
106 2. Materials and m e t h o d s Male Swiss NMRI mice (Evic Ceba) weighing 20-22 g were used. R o o m temperature was kept at 22 -+ 1 ° C. Rectal temperature (depth 2 cm) was measured using a thermistor probe. d~l-Propranolol in aqueous solution was injected intraperitoneally (i.p.) 15 min before i.p. imipramine, amphetamine and salbutamol. For reserpine interactions, drugs were administered 4 h after i.p. reserpine (2.5 m g • kg-1). Temperature was measured at 30, 60, 90 and 120 min after the last injection. Apomorphine induced hypothermia was studied b y injecting antidepressants 30 min before apomorphine (16 m g . kg -1 s.c.). Temperature was measured 30 min after apomorphine; the animals were put individually in small boxes (4.5 × 3.5 × 11 cm). Oxotremorine-induced hypothermia was studied b y injecting antidepressants 30 rain before oxotremorine (0.5 m g • kg -1 i.p.). Temperature was measured 30, 60, 90 and 120 min after oxotremorine. The potentiation of yohimbine toxicity was studied b y injecting antidepressants 30 min before s.c. yohimbine (25 mg . k g -1) and putting the animals in groups of 10 in conventional cages (28 × 16 × 10 cm). The n u m b e r of deaths was counted at 6 0 , 1 2 0 , 1 8 0 , 2 4 0 rain and 20 h. The dose of propranolol was that with the smallest hypothermia-potentiating effect.
3. Results
The results are shown in fig. 1. Propranolol on its o w n slightly potentiated reserpineinduced h y p o t h e r m i a b u t the effect varied greatly from one occasion to another. Salbutamol, imipramine and d-amphetamine
M. SOUTO ET AL. clearly antagonized the reserpine-induced hypothermia, an antagonism which was markedly reduced b y dj-propranolol pretreatment. Similarly, there was a slight b u t consistent potentiation of b o t h apomorphineand oxotremorine-induced hypothermia b y propranolol alone whereas hypothermia induced b y either c o m p o u n d was antagonized b y salbutamol, imipramine and d-amphetamine. In b o t h tests the antagonism of apomorphine- and oxotremorine-induced hypothermia was greatly reduced by pretreatment with d,l-propranolol. Yohimbine toxicity (0 or I death in 10 mice) was n o t modified b y propranolol alone b u t was increased by salbutamol, imipramine and d-amphetamine. This increased yohimbine toxicity with the three potential antidepressants was completely antagonized b y pretreatment with d,1propranolol.
4. Discussion
The results show that propranolol can antagonize the effects of salbutamol, imipramine and amphetamine in four tests predictive of antidepressant activity in man suggesting that the pharmacological effects of these three antidepressants may in part be due to stimulation o f ~-adrenergic receptors. This conclusion requires some c o m m e n t , however, because propranolol, despite the fact that the dose used was the highest having minimal hypothermic effects, itself mildly potentiated the hypothermia induced b y reserpine, apomorphine and oxotremorine. Nevertheless propranolol's potentiation of hypothermia was not as marked or consistent as its antagonism of the effects o f salbutamol, imipramine
Fig. 1. Interaction of propranolol with salbutamol, imipramine or amphetamine on antidepressant predictive tests in mice. (a) All animals received reserpine 2.5 mg • kg -1 i.p. 5 h before temperature measurement. (b) All animals received o x o t r e m o r i n e 0.5 mg • kg -1 i.p. 60 rain before temperature measurement. (c) All animals received apom o r p h i n e 16 m g . kg -1 s.c. 30 rain before temperature measurement. (d) All animals received y o h i m b i n e 25
mg • kg -1 s.c. 4 h before death numeration, d,l-Propranolol (pro), salbutamol (salb), imipramine (imi), amphetamine (amp) were injected intraperitoneally. The injection volume was 0.25 mg/20 g. The time of administration and the doses used (mg • kg -1 ) are indicated in the figure. Each result was obtained from at least 6 mice for hypothermia, 10 mice for the toxicity of yohimbine. * P < 0.05 ; ** P < 0.01, *** P < 0.001, Student's t-test.
A N T A G O N I S M O F IMIPRAMINE B Y d,I-PROPRANOLOL (~)
107
RESERPINE
Ft~ i--
oC37.
-37°C
11.O. r-'--1
-31
.26 h-T5min.
MJ 0~
)ro. 0
4
0
4
h-6Omin, salb,O
0
8 8
pro.O imi. 0
4 0 4 0 16 16
pro. 0 amp.O
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APOMORPHINE
°C38.
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34
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t0
if'
Q
0 h- 285 rain. h-270min,
2 4
wo.O 4 0 solb.O 0 4
4 4
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-s8 °c
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0
4
sdb. O 0 16 16
pro.
0
4 0
4
imi.
0 0 16 16
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pro. 0 8
0 8
omp. O 0
4 4
108
and amphetamine in these three tests, suggesting that the antagonism observed was not simply due to the intrinsic hypothermic effect of propranolol. If stimulation of ~-adrenergic receptors is a common feature of the three antidepressants tested, is ~-adrenergic stimulation common to all antidepressants? The three drugs salbutamol, imipramine and amphetamine have different mechanisms of action -- direct receptor stimulation, blockade of monoamine reuptake and stimulation of monoamine release. MAO inhibitors increase the availability of monoamines by blocking their metabolism. Other antidepressant drugs, for example mianserin, appear to act by blocking pre-synaptic a-adrenergic receptors thereby increasing the release of NA through interruption of a negative feedback system. The hypothesis can therefore be entertained that all antidepressant drugs act through a final common mechanism of ~-adrenergic stimulation.
M. SOUTO ET AL.
If so, some dysfunction in the ~-adrenergic system would seem to be implicated in the pathophysiology of depressive illness.
References Franc~s, H., A.J. Puech and P. Simon, 1978, Profil psychopharmacologique de l'isoprdnaline et du salbutamol, J. Pharmacol. (Paris) 9, 25. Franc~s, H. and P. Simon, 1978, Isoproterenol and psychopharmacological tests: Antagonism by betaadrenergic antagonists, Pharmacol. Res. Commun. 10,211. Puech, A.J., H. Franc~s, M. Souto, R. Chermat and P. Simon, 1978, Problems of pharmacological screening for antidepressants, in: Advances in Pharmacology and Therapeutics, Vol. 5, Neuropsychopharrnacology, ed. C. Dumont (Pergamon Press, Oxford--London). Simon, P., Y. Lecrubier, R. Jouvent, A.J. Puech, J.F. Allilaire and D. WidlScher, 1978, Experimental and clinical evidences of the antidepressant effect of a beta-adrenergic stimulant, Psychol. Med. 8, 335.
