Electrolytic lesions were placed bilaterally either in the anterior or in the posterior amygdala of albino rats. In terms of comparisons of lesion data with data for animals with corresponding control operations, anterior amygdaloid lesions had no significant influence on either water or overall food intake nor on body weight, while posterior amygdaloid lesions significantly increased water consumption without reliably altering food intake or body weight. It is proposed that the dorsal portion of the anterior amygdala may contain neural elements which facilitate food consumption and inhibit water intake, that the posterodorsal amygdala may contain excitatory elements for food intake, and that the middle portion of the amygdala as a whole may facilitate water intake.In a previous study (Stoller, 1972), relatively large bilateral lesions situated in the amygdaloid complex of rats decreased water intake and produced a loss of body weight. In addition, the data indicated that such lesions might reduce food consumption. Although histological examination of the amygdala and neighboring structures revealed a few instances of damage to the posterior striatum (striatum = caudatoputamen nucleus), a subse· quent investigation (Stoller, 1974) suggested that striatal injury had exerted relatively little, if any, influence on the previous findings.Information has accumulated indicating that amygdaloid influences on eating and drinking are region dependent. Lesions in the dorsomedial amygdala, for example, have resulted in aphagia (Fonberg, 1969), whereas damage involving the basolateral region has produced hyperphagia (Green, Clemente , & De Groot, 1957). Collier and Gault (1969) observed both aphagia and adipsia as a result of lesions involving the medial nuclei. Grossman and Grossman (1963) found that, in rats, water intake was reduced by lesions in the anterior or middle portion of the ventral amygdala, but was increased by posteroventrally placed lesions. More recently Box and Mogenson (1975) observed that lesions in the dorsal region of the central amygdaloid nucleus of the rat produced aphagia and adipsia, whereas lesions in the ventral posterior portion of the lateral amygdala resulted in hyperphagia.In view of such findings the present study sought to extend the analyses of the previous investigations in this laboratory (Stoller, 1972(Stoller, , 1974) to a comparison of the possible effects of anterior and posterior amyg· daloid lesions on eating and drinking.
Albino rats were trained on a visual discrimination task for which leverpressing in the presence of a cuelight was continuously reinforced with food. Upon attainment of criterion, the rats received bilateral electrolytic lesions in either the anterior or the posterior amygdala, or were subjected to a corresponding control operation. For both placement sites, the discriminative behavior of the lesioned animals, as well as their activity in an open field, was comparable to that of the corresponding controls. The results are discussed in terms of possible excitatory and inhibitory amygdaloid influences on appetitively motivated instrumental behavior and are interpreted in relation to previous research. It is proposed that the middle portion of the amygdala as a whole may exert an excitatory influence on appetitive arousal.
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