Effect of paraventricular nucleus lesion and cold restraint stress on gastric emptying of a liquid meal in rats

RESUMO

The effects of cold restraint stress on gastric emptying (GE) and the involvement of the hypothalamic paraventricular nucleus (PVN) were investigated in male Wistar rats (200-250 g body weight). Electrolytic lesions were produced stereotaxically in the nucleus by passing a 2.0-mA current for 10 s through stainless steel electrodes. GE was measured by means of a liquid test meal of 5 per cent (w/v) glucose solution plus phenol red (6 mg/dl) dye as marker, given by orogastric infusion. Cold restraint stress induces a significant increase (43.7 per cent , N = 11) in gastric retention of a 5 per cent glucose solution in rats, i.e., a delay in GE of this solution. However, restraint stress alone does not produce any change. Both truncal vagotomy and electrolytic lesion of the PVN completely block the cold restraint-induced delay in GE. However, PVN lesion per se results in a decrease of GE (30.6 per cent , N = 10) when compared to nonoperated controls. In addition, PVN-lesioned rats exposed to cold restraint present a slightly faster GE (14.7 per cent , N = 11) than controls, demonstrating an opposite response to that initially observed without lesion. These data suggest an important role for PVN efferents, probably influencing medullary vagal preganglionic neurons, in the development of this gastric motor impairment under stress conditions