Damage to the central amygdala produces differential encephalic c-fos expression in the water deprivation-partial rehydration protocol

Abstract

We investigated the effects of electrolytic damage to the central nucleus of the amygdala on brain c-fos expression and 0.3 M NaCl intake of adult male rats (n=6-12/group) submitted to a cycle of 36 h of water deprivation (WD) followed by 2 h water intake until satiety or partial rehydration (PR). The groups were divided into sham lesion (CEAs), bilateral lesion of the CEA (CEAX) and misplaced lesion with intact CEA (CEAm). The WD-PR produced a marked increase in c-fos expression in the medial parabrachial nucleus (MPBN) and some increase in the parvocelullar portion of the hypothalamic paraventricular nucleus (PVNp), compared to respective hydrated control (no water deprivation) state in CEAX, but not in CEAs or CEAm. The WD-PR induced similar c-fos expression in the lamina terminalis, supraoptic nucleus, magnocellular PVN and lateral parabrachial nucleus in both CEAX and CEAs. The CEAX showed the typical reduced daily need-free 0.3 M NaCl intake compared to CEAs. However, the 0.3 M NaCl intake of CEAX, unexpectedly, was not significantly different from CEAs or intact rats in the sodium appetite test that followed a cycle of WD-PR. The results do not allow associating the alterations in c-fos expression to the typical inhibition of sodium appetite well known in the literature to be produced by damage to the CEA. Nevertheless, the enhanced cell activation in the MPBN and PVNp suggests an inhibitory role for the CEA on the activity of these nuclei when water-deprived rats have quenched their thirst. (C) 2009 Elsevier B.V. All rights reserved.