EFFECT OF PARAVENTRICULAR NUCLEUS LESION AND COLD RESTRAINT STRESS ONGASTRIC-EMPTYING OF A LIQUID MEAL IN RATS

The effects of cold restraint stress on gastric emptying (GE) and the involvement of the hypothalamic paraventricular nucleus (PVN) were inv estigated in male Wistar rats (200-250 g body weight). Electrolytic le sions 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% (w/v) glucose solution plus pheno l red (6 mg/dl) dye as marker, given by orogastric infusion. Cold rest raint stress induces a significant increase (43.7%, N = 11) in gastric retention of a 5% glucose solution in rats, i.e, a delay in GE of thi s solution. However, restraint stress alone does not produce any chang e. 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%, N = 10) when compared to nonop erated controls. In addition, PVN-lesioned rats exposed to cold restra int present a slightly faster GE (14.7%, N = 11) than controls, demons trating an opposite response to that initially observed without lesion . These data suggest an important role for PVN efferents, probably inf luencing medullary vagal preganglionic neurons, in the development of this gastric motor impairment under stress conditions.