Effects of chemical injection into the reticular formation of rats.

Abstract

In order to demonstrate a continuum of arousal and relate with the performance of instrumental responses, chemical solutions were injected through implanted cannulae into the mesencephalic reticular formation of unrestrained rats. Neural excitants produced alertness and fear, and after repeated injections caused generalized convulsions. Neural depressants produced a hyperactive "delirious" state, which, if the injection was repeated, was abruptly followed by coma without intervening drowsiness or sleep. In both high and low arousal states, the performance of instrumental responses was suppressed, showing a curvilinear relationship between arousal level and performance.