OLFACTORY BULB ABLATION IN THE RAT: BEHAVIOURAL CHANGES AND THEIR REVERSAL BY ANTIDEPRESSANT DRUGS

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Abstract
1 The effects of bilateral olfactory bulbectomy, sham-operation and inducement of peripheral anosmia were studied on locomotor activity, passive avoidance acquisition and irritability. 2 Bulbectomized rats were hyperactive, deficient at learning a step-down passive avoidance response and hyperirritable. Peripheral anosmia, induced by intranasal infusion of ZnSO4 solution resulted in no behavioural changes. 3 Chronic pretreatment with amitriptyline (3 and 10mg/kg) and a tetracyclic antidepressant mianserin (Org GB 94, 5 and 15 mg/kg) reversed the hyperactivity and reduced the learning deficit of bulbectomized rats. These drugs had no significant effects on sham-operated animals. 4 Neither amitriptyline nor mianserin reduced the exaggerated responses of bulbectomized rats to external stimuli. 5 (+)-Amphetamine (1 and 3 mg/kg) accelerated the acquisition of the passive avoidance response, greatly enhanced the locomotor activity and slightly increased the irritability score of both sham-operated and bulbectomized rats. 6 Chlorpromazine (1 and 3 mg/kg) and chlordiazepoxide (10 mg/kg) significantly reduced the acquisition, locomotor activity and irritability of experimental and control rats. 7 Lithium sulphate (1 and 3 mg/kg) had no effect on activity or irritability but produced a small impairment in acquisition of bulbectomized rats. 8 It is concluded that the reversal by antidepressant drugs of the behavioural syndrome seen after olfactory bulb ablation could constitute a new model for the detection of this group of centrally acting compounds.