In this investigation, quantitative characteristics of vocalization, fighting, biting and convulsions elicited by carbachol injected into the cerebral ventricle of unanesthetized cats have been studied. Fighting, biting and convulsions were dose-dependent and long-lasting, their ED50 values being 0.008 mg, 0.018 mg and 0.047 mg respectively. The value of ED50 for vocalization is less than 0.005 mg. When using small doses the entire aggressive behavior pattern could be divided into its elements (vocalization, fighting, biting); however with larger doses it was not possible to obtain a separation of effects. These results support the view that there are central cholinoceptors of different sensitivity subserving aggressive behavior and convulsions. The fact that carbachol produces long-lasting aggressive behavioral effects further supports the view that the mechanisms activated by this cholinomimetic agent differ from conventional synaptic transmission. It follows then that cholinoceptive neurones activated by carbachol subserve physiological functions or pathological changes of long duration.
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