Lesions of the amygdala central nucleus interfere with blockade of satiation for peanut oil by Na-2-mercaptoacetate

Abstract

Previous research suggests that the amygdala central nucleus (CN) is an important neuroanatomical substrate for energy balance, and the detection of lipoprivic state signals in particular. We recently demonstrated that rats with selective lesions of the CN did not show enhanced conditioned reponding toward oil-predicting stimuli after administration of the lipoprivic agent, Na-2-mercaptoacetate (MA; Benoit, Morell, and Davidson, 1999). In the present experiment, rats with lesions of the CN were trained in such a way that a stimulus predicted the delivery of either sucrose pellets or peanut oil under food deprivation. They were then given access to the foods under food satiation after an injection of either saline or MA. Finally, rats received a behavioral test for learned satiation responses to the stimulus (i.e., reduced responding) in the absence of food or MA. Results showed that MA blocked acquisition of satiation responses in rats trained with peanut oil, but not sucrose. Rats with lesions of the CN, however, acquired satiation responses equally, regardless of macronutrient or treatment. These data extend previous findings suggesting that the CN is a critical brain structure for rats' ability to detect lipoprivation and introduce an additional behavioral paradigm for the study of macronutrient selection.