Fos expression and hormone changes following electrical stimulation of the posterodorsal amygdala and the effects on food intake in conscious female rats

Previous studies have shown that lesions of the posterodorsal amygdala (PDA) produce hyperphagia and obesity in female rats. To better understand the role of the PDA in the regulation of feeding behavior, the current study examined the effects of electrical stimulation of the PDA of female rats on food intake and identified neurons activated by PDA stimulation using Fos immunohistochemistry. Hormonal levels following stimulation of the PDA were also investigated. Electrical stimulation (100 mu A, 0.2 ms, 20 Hz, 10 min) of the PDA remarkably decreased I h food intake of rats. Following PDA stimulation, the number of Fos-like immunoreactive neurons increased in the caudal and intermediate parts of the nucleus of the solitary tract (NST), the area postrema. (AP), the external lateral submicleus of the parabrachial nucleus (PBN), the arcuate nucleus of the hypothalamus (Arc), and the central amygdaloid nucleus (CeA). The level of circulating leptin was elevated significantly by PDA stimulation as well. Together with previous studies, the results suggest that the PDA may play an important role in the regulation of feeding behavior, at least partly by modulating the circulating leptin, and that the caudal and intermediate parts of the NST, AP, external lateral PBN, Arc, and CeA probably participate in this regulation. (C) 2009 Elsevier B.V. All rights reserved.