Forebrain noradrenaline depletion blocks the release by chlordiazepoxide of behavioral extinction in the rat.

The interaction between chlordiazepoxide (CDP) and forebrain noradrenaline (NA) was investigated in rats with bilateral radiofrequency lesions of the noradrenergic dorsal tegmental bundle (DTB). Forebrain NA was reduced to 35% of control by the DTB lesions; hypothalamic NA and dopamine were unchanged. Rats were trained on a straight alley runway task for food reward. During extinction of the runway task, CDP significantly increased extinction responding in sham lesion animals but not in DTB lesion animals. Thus, CDP was ineffective in increasing resistance to extinction responding in the runway task in animals with significant depletion of forebrain NA.