Colonic motility in the cat. IV. Peripheral pathways mediating the effects induced by hypothalamic and mesencephalic stimulation.

Abstract

Rostad, H. Colonic motility in the cat. IV. Peripheral pathways mediating the effects induced by hypothalamic and mesencephalic stimulation. Acta physiol. scand. 1973. 89. 154–168. The peripheral pathways by which the hypothalamus and mesencephalon influence the motility of the colon have been studied by combining brain stimulation and peripheral nerve sectioning, and by use of autonomic blocking agents. Excitatory colonic effects induced from the hypothalamic sympatho-inhibitory area with concomitant blood pressure falls were found to be mediated through the sympathetic lumbar colonic nerves, whereas excitatory responses with associated blood pressure rises were conveyed through the latter as well as through the parasympathetic pelvic nerves. On the other hand, the augmentatory colonic effects usually associated with blood pressure rise evoked from the mesencephalon were conveyed through the lumbar colonic nerves only. The responses through the lumbar colonic and pelvic nerves were blocked by guanethidine and atropine, respectively. The augmentatory colonic responses from the hypothalamic sympatho-inhibitory area were blocked by the beta-adrenergic blocking agent propranolol, whereas the effects from the other responsive hypothalamic areas, transmitted through the lumbar colonic nerves, were blocked by alpha-blocker (phenoxybenzaminc), but not by propranolol. This finding support the presence of alpha-excitatory receptors in the colonic wall. Inhibition of colonic motility induced by hypothalamic and mesencephalic stimulation, weir found to be mediated through the lumbar colonic as well as through the splanchnic nerves. The effects were blocked by guanethidine, and those from the responsive hypothalamic zones were also blocked by propranolol.