Double dissociation of the behavioural effects of R(+) 7-OH-DPAT infusionsin the central and basolateral amygdala nuclei upon Pavlovian and instrumental conditioned appetitive behaviours

Dopaminergic cell bodies located within the ventral mesencephalon innervate the amygdaloid complex, a region critically involved in the attribution of affective significance to environmental stimuli. Recently, we have shown t hat post-session intra-amygdala administration of a Dg dopamine receptor ag onist enhances selectively the acquisition of an appetitive conditioned res ponse. In the present study, we have investigated the potential involvement of the central nucleus and the basolateral nuclei of the amygdala in media ting this effect. Thus, rats were trained to associate an arbitrary stimulu s (CS+) with the availability of 10% sucrose reward. Post-session infusions of the D-3 receptor-preferring agonist, R(+) 7-OH-DPAT, were made into eit her the central nucleus or basolateral nuclei. Acquisition of a conditioned approach response was enhanced by R(+) 7-OH-DPAT infusions within the cent ral nucleus, but not within the basolateral nuclei. Drug infusions into eit her region failed to affect approach behaviour elicited by presentation of a control stimulus (CS-), explicitly unpaired with sucrose reward. The effe cts of pre-test infusions of R(+) 7-OH-DPAT on the instrumental properties of the stimuli were then determined. Rats were presented with two novel lev ers, depression of one lever resulted in presentation of the CS+, while pre sentation of the CS- was contingent upon depression of the other lever. Rat es of response upon each lever as well as the ability of the conditioned st imuli subsequently to elicit conditioned approach behaviour were recorded. Data revealed a double dissociation of the effects of R(+) 7-OH-DPAT on the expression of the Pavlovian and instrumental properties of the reward-rela ted stimulus. Thus, within the central nucleus R(+) 7-OH-DPAT dose-dependen tly attenuated expression of the conditioned approach response, but had no effect upon instrumental responding maintained by the conditioned reward. I n contrast, within the basolateral nuclei, R(+) 7-OH-DPAT had no effect upo n expression of conditioned approach behaviour, but abolished selectively t he ability of the reward-associated stimulus to support the acquisition of a novel instrumental response. Hence, these data indicate that distinct reg ions of the amygdaloid complex process distinct aspects of conditioned appe titive behaviours.