SOME STUDIES ON DRUG-INDUCED BEHAVIOUR IN YOUNG CHICKS

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SOME STUDIES ON DRUG-INDUCED BEHAVIOUR IN YOUNG CHICKS

Abstract:

Some behavioural and electrophysiological studies were undertaken in chicks and rats using observational, EEG, EMG and evoked potential techniques. Some dopamine (DA) agonists (apomorphine, d-amphetamine, amantadine, and piribedil) induced stereotyped pecking activity and aggressive behaviour of varying intensities in chicks. On the other hand, DA, L-dopa and ergometrine did not induce characteristic stereotyped activity in the chicks. D-amphetamine and ergometrine induced distinct postural changes in chicks. Pretreatment of chicks with ergometrine and piribedil antagonized the behavioural effects of apomorphine and d-amphetamine. The results show that apomorphine d-amphetamine, amantadine and piribedil induce a similar pattern of stereotyped activity in young chicks. The results further suggest that X ergometrine exerts a predominant inhibitory influence on stereotyped behaviour , while piribedil has both DA agonistic and antagonistic effects in young chicks. Pretreatment of chicks with reserpine and 6-hydroxydoparaine (6-OHDA) potentiated apomorphine and piribedil-induced stereotyped behaviour while the effects of d-amphetamine and amantadine were inhibited. The behavioural effect of apomorphine were potentiated when chicks were pretreated with dihydroxy-phenylserine, while d-amphetamine and amantadine effects were antagonised. FLA–63 potentiated d-amphetamine and amantadine-induced stereotyped behaviour and inhibited apomorphine effects. Propranolol antagonized the behavioural effects of apomorphine and d-amphetamine, while phenoxybenzamine slightly potentiated the effects. Pimozide and haloperidol antagonized apomorphine, d-amphetamine, amantadine and piribedil-induced stereotyped behaviour. These observations indicate a primary role for VT dopaminergic system in drug-induced stereotyped behaviour in young chicks as in other species. Serotonin and quipazine antagonized apomorphine and d-amphetamine-induced stereotyped behaviour. On the other hand, cyproheptadine and parachloro-phenylalanine (PCPA) potentiated the effects of apomorphine and d-amphetamine. These results suggest that serotonergic system plays an inhibitory role in drug-induced stereotyped behaviour in chicks. Desipraraine, imipramine and amitriptyline induced biphasic locomotor effects in chicks. Aporaorphine-induced locomotor activity was potentiated when the chicKs were pretreated 30 rain, previously with amitriptyline and imipramine. When the three antidepressants were administered 1 h previously, apomorphineinduced locomotor activity was inhibited. The results suggest that tricyclic antidepressants produce a time-dependent effect on apomorphine-induced locomotor activity in XII chicks. Repeated administration of j3,i$’-iminodipropionitrile( IDPN) for five days induced specific behavioural changes in chicks. These behavioural changes were characterized by excitation which was accompanied by loud chirping, jerky head and neck movements, and circling motion (i.e. ECC-syndrome). Amphetamine potentiated the syndrome while apomorphine and piribedil enhanced the head and neck movements with minimal effect on the circling behaviour. Pimozide antagonized the ECC-syndrome and also inhibited amphetamine-induced potentiation of the syndrome. Atropine and hyoscine enhanced the ECC-syndrome and also potentiated the effects of d-amphetamine, while physostigmine antagonised the syndrome. Quipazine, in low doses, abolished and in high doses enhanced the ECC-syndrome. The latter effect was antagonised by both cyproheptadine and pimozide. Such results suggest that DA and I I serotonergic mechanisms may be involved in IDPN-induced effects in chicks. It is also possible that cholinergic system may exert an inhibitory influence on the ECC-syndroioe. Evoked responses to photic stimulation recorded under artificial light and dark adaptation from three different brain areas in conscious young chicks were compared. The magnitude of the evoked responses varied from one experiment to another, but for a particular chick consistent responses were obtained under the same behavioural state, stimulus intensity, and recording conditions. The evoked responses recorded under dark adaptation were larger in magnitude and more reproducible when compared with those recorded..under artificial light. The photic-evoked responses under dark adaptation were very sensitive to drug effects. These observations suggest that photic-evoked response (PER) could probably be utilized in the elucidation of the actions of some :v Psychoactive drugs. The influence of acute and chronic administration of phenobarbitone and ethanol on PER was studied in rats. Both phenobarbitone and ethanol produced behavioural depression. EEG synchronization and varying effects on the averaged PER recorded from the frontal cortex (FC) optic cortex (OC) and midbrain reticular formation (MBRF). In phenobarbitone- and ethanol- dependent animals, amplitude of the PER recorded from the FC and OC were enhanced while the recordings from the MBRF were reduced. On the other hand, the amplitudes of the PER from all the three brain areas were enhanced during withdrawal. The results suggest that both phenobarbitone and ethanol produce similar effects on PER in rats and that the effects may probably be characteristic of the sedative – hypnotic group of drugs

SOME STUDIES ON DRUG-INDUCED BEHAVIOUR IN YOUNG CHICKS

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