Bleeding inhibits vagally induced duodenal HCO3- secretion via activation of the splanchnic nerves in anaesthetized rats.

This study was performed on chloralosed rats in order to examine the influence of a minor blood loss on duodenal HCO3- secretion. The HCO3- output was measured by in situ titration in a duodenal segment. Blood loss of 0.3 ml per 100 g body wt (approximately 5% of total blood volume) and 0.6 ml per 100 g body wt (approximately 10% of total body volume) reduced duodenal HCO3- secretion by about 18 and 31%, respectively. Adrenal ligation increased basal output of HCO3- but did not affect the bleeding-induced response. Thoracic epidural anaesthesia or splanchnicotomy did not affect the basal secretion but markedly reduced the depression of duodenal HCO3- secretion due to blood loss. Vagotomy lowered basal duodenal HCO3- secretion and blood loss did not reduce alkaline output in these animals. However, electric stimulation of the cut vagal nerves raised the duodenal HCO3- secretion to a similar level as in rats with intact vagal nerves. In this group blood loss reduced the duodenal HCO3- output as in rats with intact nerves. It is suggested that a small blood loss, via an activation of the sympathetic nervous system, reduces the vagally controlled part of the duodenal HCO3- secretion and that this effect is conveyed in the splanchnic nerves.