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Effect of histaminergic drugs on footshock-induced aggressive behaviour in rats
European Journal of Pharmacology, 73 (1981) 217-219 Elsevier/North-Holland Biomedical Press
217
Short communication EFFECT OF HISTAMINERGIC DRUGS ON FOOTSHOCK-INDUCED AGGRESSIVE BEHAVIOUR IN RATS ARUNAVA RAY, KRISHNA K. SHARMA and PARANTAPA SEN *
Department of Pharmacology, University College of Medical Sciences, New Delhi 110 029, India Received 27 May 1981, accepted 3 June 1981
A. RAY, K.K. SHARMA and P. SEN, Effect of histaminergic drugs on footshock-induced aggressive behaviour in rats, European J. Pharmacol. 73 (1981) 217-219. Histamine and 2-pyridylethylamine decreased and 4-methylhistamine increased footshock-induced aggression after their intracerebroventricular administration to rats. Mepyramine and cimetidine had no effect on the fighting response but blocked the effects of the respective agonists. Histamine when given after mepyramine increased and after cimetidine decreased the fighting score, this decrease being more than that with histamine alone. It is inferred that central Hi-receptors are inhibitory and H2-receptors facilitatory in footshock aggression and that this is independent of catecholaminergic mechanisms. Footshock aggression
2-Pyridylethylamine
4-Methylhistamine
1. Introduction
Evidence is accumulating that histamine (HA) is a neurotransmitter in the central nervous system (Schwartz, 1977). However, clear assignment of a physiological role for HA in various body functions and behaviours is lacking although intracerebroventricular (i.c.v.) administration of this amine has been shown to produce a number of behavioural effects ranging from an increase in water intake (Gerald and Maickel, 1972), hypomotility, depression of the avoidance response (Calcutt and Reynolds, 1976), elevation of the self stimulation threshold (Cohn et al., 1973), hypothermia (Green et al., 1976) and catalepsy (Jagiello -Wojtowicz, 1973) in rats. These apparent neurotransmitter actions of HA have been shown to be mediated via either H~-, H 2- or both receptors. The possibility of a hitherto unknown type of histamine receptor cannot be denied as some effects of HA were not blocked by H~- or H 2receptor antagonists (Calcutt and Reynolds, 1976). In the present study, we have investigated the effect of HA and selective agonists of HI- and H2-receptors on footshock-induced aggressive be* To whom correspondence should be addressed.
Mepyramine
Cimetidine
Histamine
haviour in rats. Further, we have studied any possible interrelationship of HA with catecholamines since previous studies have shown that HA stimulates the release of catecholamines in brain (Subramanian and Mulder, 1977; Subramanian, 1979), and both dopamine (facilitatory) and noradrenaline (inhibitory) are involved in the footshock-induced aggressive behaviour (Daruna, 1978).
2. Materials and methods
Male albino rats (150-180 g) which showed at least one fighting score in 1 min period of footshock were selected for the study. In all animals, chronic polyethylene (PE-10) cannulae were implanted 4 mm deep into the lateral ventricle (Noble et al., 1967) under pentobarbitone anaesthesia (40 mg/kg i.p.). A 4 mm anchoring optical screw was placed skull deep, 1.5 mm anterolateral to the bregma and both the screw and cannula were fixed to the skull with dental acrylic cement. The animals were kept individually in shoe box plastic cages and used 72 h after cannulation. One pair of rats was footshocked at a time in an aggressometer (Techno Electronics) before and
0014-2999/81/0000-0000/$02.50 © Elsevier/North-Holland Biomedical Press
218
after drug administration, for 3 min. The stimulation parameters were: 150 V, 0.5 mA, 5 shocks/sec (intershock interval 200 msec, pulse duration 5 msec). On footshock, the animals stood face to face on their hindlimbs and struck at, wrestled with or bit (with or without bleeding) at each other. One strike with forelimbs was scored as 1, one wrestling bout as 2, one bite without bleeding as 3 and one bite with bleeding as 4. The total score in a 3 min period of footshock was counted with the help of a digital counter. The drugs used were: histamine diphosphate (Sigma), 2-pyridylethylamine hydrochloride (2PEA, H l-agonist), 4-methylhistamine (4MHA, H2-agonist ), cimetidine (H2-antagonist) (all from Smith Kline & French), mepyramine maleate (Anthisan ampoules, May and Baker) and amethyl-p-tyrosine methylester hydrochloride (AMT, Sigma). All drugs were dissolved in physiological saline except cimetidine which was dissolved in a minimal quantity of 0.5 N HC1 and neutralised with 0.5 N NaOH to attain a pH of 6.0 then diluted to an appropriate volume with saline. All drugs were administered i.c.v, in a volume of 20 #1 over a period of 10 sec except AMT, which
was injected intraperitoneally (i.p.) in a vol of 5 ml/kg. Both rates in a pair received the same drug treatment. The fighting score was determined 15 min after an agonist, 30 min after an antagonist and 4 h after AMT administration. Before the animals were put in the aggressometer, they were tested for the effect of drugs on pain sensitivity. This was done with the tail-flick response in a resistance wire (0.5 f2/cm, at 6.5 A) analgesiometer. An observer who was not aware of the drug treatment assessed the response. The results were analysed statistically with Student's t-test.
3. Results
The footshock-induced fighting score was significantly reduced (P<0.001) after administration of HA and of the H~-receptor agonist, 2PEA (table 1). However, 4MHA, and H:-receptor agonist increased the fighting score significantly (P<0.001). Administration of HA to mepyraminetreated animals increased the fighting score whereas the score was reduced (P<0.001) in
TABLE 1 Effect of histamine and selective Ht- and H2-receptor agonists and antagonists on footshock-induced aggressive behaviour in rat. Drugs
Saline Histamine (HA) 2-Pyridylethylamine (2PEA) 4-Methylhistamine (4MHA) Mepyramine (MEP) Cimetidine (CIM) M E P + HA C I M + HA MEP + 2PEA CIM+4MHA a-Methyl-p-tyrosine (AMT) A M T + HA A M T + 2PEA AMT+4MHA
Dose ( # g / r a t i.c.v.), 20/~1 5 20 20 30 40 ** ** ** ** 150 m g / k g i.p. ** ** **
Pretreatment time (min)
Fighting score (mean ± S.E.M.) * Before drug
After drug
15 15 15 15 30 30 ** ** ** ** 4h
112.5 _ 6.25 100.0±4.92 97.8 ± 3.68 11 I. 1 ± 4.49 96.0 ± 3.96 107.2 ± 3,44 104.1 ± 4 . 2 8 123.4±4.08 127.2 ± 4,41 123.0±5.04 106.5 ± 5.52
115.0 ~ 5.82 68.0±4.11 a 33.3 ± 2.96 a 164.2 ___6.61 a 109.0 ± 4.45 98.0 ± 4.09 163,0±5.65 a 41,4±4.78 a,c 120.0 ± 3.03 116.2-----5.93 98.0 ± 4.82 b
** ** **
115.4___5,23 104.4±6.0 101.8±5.72
62.2±4.67 a,d 45.4±5.33 a,d 152.7±6.97 a'd
* Five pairs of rats were used for each set of experiments. ** The d o s e , route and the pretreatment times were the same as for individual drugs. a P
219
cimetidine-treated animals. This reduction in fighting response by HA in cimetidine-treated animals was significantly greater (P<0.01) than that observed with HA alone. Mepyramine and cimetidine as such did not produce a significant change (P>0.05) in the fighting response when compared to that of the saline controls, but blocked the effects of their respective agonists, 2PEA and 4MHA. Pretreatment with AMT did not alter the effect of HA, 2PEA and 4MHA on the fighting score. Control animals treated with physiological saline i.c.v, did not reveal any change in fighting scores. At the doses used, none of the drugs produced a significant change (P>0.05) in the latency of the tail-flick response. Also there was no visible change in locomotor behaviour in the cage after various drugs when compared with saline-treated animals, except after mepyramine and AMT, both of which lowered activity without producing catalepsy.
been shown to release dopamine and noradrenaline from various regions of the brain (Subramanian and Mulder, 1977; Subramanian, 1979) suggesting a neuromodulatory role of this amine in the catecholaminergic processes in the CNS, it was necessary to rule out the mediation of effect of histaminergic drugs by catecholamine release. The results with AMT, a catecholamine synthesis inhibitor, show that the changes produced in footshock-induced aggressive behaviour by histamine, and by H l- and H2-receptor stimulation are independent of catecholaminergic mechanisms.
Acknowledgements The authors are grateful to Dr. M. Alkondon for useful discussions during the study and Mr. T. Khanna for skillful technical assistance.
References 4. Discussion The results of this study indicate clearly that both H l - and H2-receptors are involved in footshock-induced aggressive behaviour in rats. However, the effects mediated by these two receptors are of opposite nature. Whereas the H~receptor is inhibitory, the H2-receptor seems to have a facilitatory role. Since HA, which stimulates both H~- and H2-receptors, produced an inhibitory effect, H~-receptor activity appears to play a dominant role. The observation that HA produced a greater reduction in the fighting score in cimetidine-treated animals than did HA alone, lends further support to this view. The effect of histaminergic drugs on the fighting score could not have been due to changes in pain sensitivity since none of these drugs altered the tail-flick latency in the doses used. Previous studies have suggested that noradrenaline was inhibitory and dopamine fac.ilitatory in the modulation of footshock-induced aggressive behaviour (vide rev. Daruna, 1978). Since HA has
Calcutt, C.R. and J. Reynolds, 1976, Some behavioural effects following intracerebroventricular injection in rats of histamine H~ and H 2 receptor agonists and antagonists, Neurosci. Lett. 3, 82. Cohn, C.K., G.G. Ball and J. Hirsch, 1973, Histamine: Effects on self stimulation, Science 180, 757. Daruna, J.H., 1978, Patterns of brain monoamine activity and aggressive behaviour, Neurosci. Biobehav. Rev. 2, 101. Gerald, M.C. and R.P. Maickel, 1972, Studies on the possible •role of brain histamine in behaviour, Br. J. Pharmacol. 64, 462. Green, M.D., B. Cox and P. Lomax, 1976, Histamine H l and H 2 receptors in the central thermoregulatory pathways of the rat, J. Neurosci. Res. 1,353. Jagiello-Wojtowicz, E., 1973, The central action of histamine. 1. The effect of intraventricular histamine on rat behaviour, Pol. J. Pharmacol. Pharm. 25, 503. Noble, E.P., R.J. Wurtman and J. Axelrod, 1967, A simple and rapid method for injecting 3H-norepinephrine into the lateral ventricle of the rat brain, Life Sci. 6, 281. Schwartz, J.C., 1977, Histaminergic mechanisms in brain, Ann. Rev. Pharmacol. Toxicol. 17, 325. Subramanian, N., 1979, Depletion of noradrenaline in rat brain by histamine, Indian J. Pharmacol. 11, 177. Subramanian, N. and A.H. Mulder, 1977, Modulation.by histamine of the release of radiolabelled catecholamines from rat brain tissue slices, European J. Pharmacol. 43, 143.
217
Short communication EFFECT OF HISTAMINERGIC DRUGS ON FOOTSHOCK-INDUCED AGGRESSIVE BEHAVIOUR IN RATS ARUNAVA RAY, KRISHNA K. SHARMA and PARANTAPA SEN *
Department of Pharmacology, University College of Medical Sciences, New Delhi 110 029, India Received 27 May 1981, accepted 3 June 1981
A. RAY, K.K. SHARMA and P. SEN, Effect of histaminergic drugs on footshock-induced aggressive behaviour in rats, European J. Pharmacol. 73 (1981) 217-219. Histamine and 2-pyridylethylamine decreased and 4-methylhistamine increased footshock-induced aggression after their intracerebroventricular administration to rats. Mepyramine and cimetidine had no effect on the fighting response but blocked the effects of the respective agonists. Histamine when given after mepyramine increased and after cimetidine decreased the fighting score, this decrease being more than that with histamine alone. It is inferred that central Hi-receptors are inhibitory and H2-receptors facilitatory in footshock aggression and that this is independent of catecholaminergic mechanisms. Footshock aggression
2-Pyridylethylamine
4-Methylhistamine
1. Introduction
Evidence is accumulating that histamine (HA) is a neurotransmitter in the central nervous system (Schwartz, 1977). However, clear assignment of a physiological role for HA in various body functions and behaviours is lacking although intracerebroventricular (i.c.v.) administration of this amine has been shown to produce a number of behavioural effects ranging from an increase in water intake (Gerald and Maickel, 1972), hypomotility, depression of the avoidance response (Calcutt and Reynolds, 1976), elevation of the self stimulation threshold (Cohn et al., 1973), hypothermia (Green et al., 1976) and catalepsy (Jagiello -Wojtowicz, 1973) in rats. These apparent neurotransmitter actions of HA have been shown to be mediated via either H~-, H 2- or both receptors. The possibility of a hitherto unknown type of histamine receptor cannot be denied as some effects of HA were not blocked by H~- or H 2receptor antagonists (Calcutt and Reynolds, 1976). In the present study, we have investigated the effect of HA and selective agonists of HI- and H2-receptors on footshock-induced aggressive be* To whom correspondence should be addressed.
Mepyramine
Cimetidine
Histamine
haviour in rats. Further, we have studied any possible interrelationship of HA with catecholamines since previous studies have shown that HA stimulates the release of catecholamines in brain (Subramanian and Mulder, 1977; Subramanian, 1979), and both dopamine (facilitatory) and noradrenaline (inhibitory) are involved in the footshock-induced aggressive behaviour (Daruna, 1978).
2. Materials and methods
Male albino rats (150-180 g) which showed at least one fighting score in 1 min period of footshock were selected for the study. In all animals, chronic polyethylene (PE-10) cannulae were implanted 4 mm deep into the lateral ventricle (Noble et al., 1967) under pentobarbitone anaesthesia (40 mg/kg i.p.). A 4 mm anchoring optical screw was placed skull deep, 1.5 mm anterolateral to the bregma and both the screw and cannula were fixed to the skull with dental acrylic cement. The animals were kept individually in shoe box plastic cages and used 72 h after cannulation. One pair of rats was footshocked at a time in an aggressometer (Techno Electronics) before and
0014-2999/81/0000-0000/$02.50 © Elsevier/North-Holland Biomedical Press
218
after drug administration, for 3 min. The stimulation parameters were: 150 V, 0.5 mA, 5 shocks/sec (intershock interval 200 msec, pulse duration 5 msec). On footshock, the animals stood face to face on their hindlimbs and struck at, wrestled with or bit (with or without bleeding) at each other. One strike with forelimbs was scored as 1, one wrestling bout as 2, one bite without bleeding as 3 and one bite with bleeding as 4. The total score in a 3 min period of footshock was counted with the help of a digital counter. The drugs used were: histamine diphosphate (Sigma), 2-pyridylethylamine hydrochloride (2PEA, H l-agonist), 4-methylhistamine (4MHA, H2-agonist ), cimetidine (H2-antagonist) (all from Smith Kline & French), mepyramine maleate (Anthisan ampoules, May and Baker) and amethyl-p-tyrosine methylester hydrochloride (AMT, Sigma). All drugs were dissolved in physiological saline except cimetidine which was dissolved in a minimal quantity of 0.5 N HC1 and neutralised with 0.5 N NaOH to attain a pH of 6.0 then diluted to an appropriate volume with saline. All drugs were administered i.c.v, in a volume of 20 #1 over a period of 10 sec except AMT, which
was injected intraperitoneally (i.p.) in a vol of 5 ml/kg. Both rates in a pair received the same drug treatment. The fighting score was determined 15 min after an agonist, 30 min after an antagonist and 4 h after AMT administration. Before the animals were put in the aggressometer, they were tested for the effect of drugs on pain sensitivity. This was done with the tail-flick response in a resistance wire (0.5 f2/cm, at 6.5 A) analgesiometer. An observer who was not aware of the drug treatment assessed the response. The results were analysed statistically with Student's t-test.
3. Results
The footshock-induced fighting score was significantly reduced (P<0.001) after administration of HA and of the H~-receptor agonist, 2PEA (table 1). However, 4MHA, and H:-receptor agonist increased the fighting score significantly (P<0.001). Administration of HA to mepyraminetreated animals increased the fighting score whereas the score was reduced (P<0.001) in
TABLE 1 Effect of histamine and selective Ht- and H2-receptor agonists and antagonists on footshock-induced aggressive behaviour in rat. Drugs
Saline Histamine (HA) 2-Pyridylethylamine (2PEA) 4-Methylhistamine (4MHA) Mepyramine (MEP) Cimetidine (CIM) M E P + HA C I M + HA MEP + 2PEA CIM+4MHA a-Methyl-p-tyrosine (AMT) A M T + HA A M T + 2PEA AMT+4MHA
Dose ( # g / r a t i.c.v.), 20/~1 5 20 20 30 40 ** ** ** ** 150 m g / k g i.p. ** ** **
Pretreatment time (min)
Fighting score (mean ± S.E.M.) * Before drug
After drug
15 15 15 15 30 30 ** ** ** ** 4h
112.5 _ 6.25 100.0±4.92 97.8 ± 3.68 11 I. 1 ± 4.49 96.0 ± 3.96 107.2 ± 3,44 104.1 ± 4 . 2 8 123.4±4.08 127.2 ± 4,41 123.0±5.04 106.5 ± 5.52
115.0 ~ 5.82 68.0±4.11 a 33.3 ± 2.96 a 164.2 ___6.61 a 109.0 ± 4.45 98.0 ± 4.09 163,0±5.65 a 41,4±4.78 a,c 120.0 ± 3.03 116.2-----5.93 98.0 ± 4.82 b
** ** **
115.4___5,23 104.4±6.0 101.8±5.72
62.2±4.67 a,d 45.4±5.33 a,d 152.7±6.97 a'd
* Five pairs of rats were used for each set of experiments. ** The d o s e , route and the pretreatment times were the same as for individual drugs. a P
219
cimetidine-treated animals. This reduction in fighting response by HA in cimetidine-treated animals was significantly greater (P<0.01) than that observed with HA alone. Mepyramine and cimetidine as such did not produce a significant change (P>0.05) in the fighting response when compared to that of the saline controls, but blocked the effects of their respective agonists, 2PEA and 4MHA. Pretreatment with AMT did not alter the effect of HA, 2PEA and 4MHA on the fighting score. Control animals treated with physiological saline i.c.v, did not reveal any change in fighting scores. At the doses used, none of the drugs produced a significant change (P>0.05) in the latency of the tail-flick response. Also there was no visible change in locomotor behaviour in the cage after various drugs when compared with saline-treated animals, except after mepyramine and AMT, both of which lowered activity without producing catalepsy.
been shown to release dopamine and noradrenaline from various regions of the brain (Subramanian and Mulder, 1977; Subramanian, 1979) suggesting a neuromodulatory role of this amine in the catecholaminergic processes in the CNS, it was necessary to rule out the mediation of effect of histaminergic drugs by catecholamine release. The results with AMT, a catecholamine synthesis inhibitor, show that the changes produced in footshock-induced aggressive behaviour by histamine, and by H l- and H2-receptor stimulation are independent of catecholaminergic mechanisms.
Acknowledgements The authors are grateful to Dr. M. Alkondon for useful discussions during the study and Mr. T. Khanna for skillful technical assistance.
References 4. Discussion The results of this study indicate clearly that both H l - and H2-receptors are involved in footshock-induced aggressive behaviour in rats. However, the effects mediated by these two receptors are of opposite nature. Whereas the H~receptor is inhibitory, the H2-receptor seems to have a facilitatory role. Since HA, which stimulates both H~- and H2-receptors, produced an inhibitory effect, H~-receptor activity appears to play a dominant role. The observation that HA produced a greater reduction in the fighting score in cimetidine-treated animals than did HA alone, lends further support to this view. The effect of histaminergic drugs on the fighting score could not have been due to changes in pain sensitivity since none of these drugs altered the tail-flick latency in the doses used. Previous studies have suggested that noradrenaline was inhibitory and dopamine fac.ilitatory in the modulation of footshock-induced aggressive behaviour (vide rev. Daruna, 1978). Since HA has
Calcutt, C.R. and J. Reynolds, 1976, Some behavioural effects following intracerebroventricular injection in rats of histamine H~ and H 2 receptor agonists and antagonists, Neurosci. Lett. 3, 82. Cohn, C.K., G.G. Ball and J. Hirsch, 1973, Histamine: Effects on self stimulation, Science 180, 757. Daruna, J.H., 1978, Patterns of brain monoamine activity and aggressive behaviour, Neurosci. Biobehav. Rev. 2, 101. Gerald, M.C. and R.P. Maickel, 1972, Studies on the possible •role of brain histamine in behaviour, Br. J. Pharmacol. 64, 462. Green, M.D., B. Cox and P. Lomax, 1976, Histamine H l and H 2 receptors in the central thermoregulatory pathways of the rat, J. Neurosci. Res. 1,353. Jagiello-Wojtowicz, E., 1973, The central action of histamine. 1. The effect of intraventricular histamine on rat behaviour, Pol. J. Pharmacol. Pharm. 25, 503. Noble, E.P., R.J. Wurtman and J. Axelrod, 1967, A simple and rapid method for injecting 3H-norepinephrine into the lateral ventricle of the rat brain, Life Sci. 6, 281. Schwartz, J.C., 1977, Histaminergic mechanisms in brain, Ann. Rev. Pharmacol. Toxicol. 17, 325. Subramanian, N., 1979, Depletion of noradrenaline in rat brain by histamine, Indian J. Pharmacol. 11, 177. Subramanian, N. and A.H. Mulder, 1977, Modulation.by histamine of the release of radiolabelled catecholamines from rat brain tissue slices, European J. Pharmacol. 43, 143.