Ventral tegmental area lesions differentially affect responses controlled by CS-US contiguity and response-reinforcer contingency in the rat.

Rats with electrolytic lesions of the ventral tegmental area (VTA, n = 32), or sham lesions (n = 32), were tested in four behavioral paradigms in a shuttlebox. The paradigms were designed to assess the motivational influence of CS-US contiguity and response-reinforcer contingency. The VTA lesion increased the number of shuttle responses in the paradigms involving contiguity between a warning signal and a shock, without affecting responses controlled by the contingency between shuttling and shock avoidance. Escape latency was reduced by the lesion, but the general locomotor activity of the rats was not increased.The data suggest that the VTA normally acts to inhibit behavior motivated by classically conditioned fear. The results are discussed in terms of the hypothesis that the dopaminergic projection from the VTA to the nucleus accumbens plays a role in the inhibition of emotionally motivated motor responses.