Suppressive effects of intraperitoneal and intraventricular injections of nicotine on muricide and shock-induced attack on conspecifics.

Rats were used to investigate the effect of nicotine on mouse-killing and foot shock-induced attack on conspecifics. It was found that intraperitoneal injections of nicotine (100-1000 micrograms/kg) suppressed mouse-killing in a dose dependent manner. The suppression of mouse-killing by nicotine was not blocked by hexamethonium (30 mg/kg), a peripheral nicotinic receptor blocking agent. Mecamylamine (30 mg/kg), a nicotinic blocking agent with central effects, did reduce the inhibition of attack produced by nicotine. Both intraperitoneal and intraventricular injections of nicotine suppressed shock-induced attack on conspecifics. Shock-elicited flinch, vocalization, and escape were not influenced by nicotine injections. These findings give further support to the view that muscarinic and nicotinic compounds produce antagonistic effects on certain types of attack behavior.