Abstract

We suggested that behavioural activation depends on dopamine D1 receptors and its level is regulated by a reward evaluation depending on D2 receptors. This hypothesis rests on the different effect of D1 and D2 antagonists on the microstructue of licking, and in particular on the abililty of D1 antagonism to reduce the number of licking bouts, a measure of activation, and of D2 antagonism to reduce their size, a measure of reward evaluation. In this study, we demonstrated that (a) reward devaluation produces on bout number time course an effect similar to that produced on operant responding and (b) the interaction between D1 and D2 receptors governing the activation of ingestive behaviour appears to be the same governing escape-directed behaviour, thus generalising and providing further support to our hypothesis. Then, we engaged in the study of the gender differences in the sensitization to NaCl appetite (a possible model of psychosis), through the study of the microstructure of the ingestion of salty solutions. Our results show that the sex differences in sensitization depend on the mechanisms underlying behavioural activation, consistently with the observation of a different sensitivity between the two sexes to the effects of D1 antagonism. These results might bear relevance in the understanding of the gender differences in the response to antipsychotics.

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