Central representation and opioid modulation of gastric mechanoreceptor activity in the rat

The effects of gastric distension on single-unit activity recorded from the dorsal vagal nucleus in the rat medulla have been studied using microelectrodes in anesthetized animals. Out of 97 units studied, 64 responded to gastric distension in one of four characteristic ways. It was possible to modify these gastric distension responses by iontophoretic application of Leu-enkephalin and naloxone. The predominant effect was diminution of the centrally recorded gastric distension response by Leu-enkephalin. These studies show it is possible to modulate the central representation of gastric mechanoreceptor activity by an opioid peptide that is common to both the gut and the brain. It is suggested these studies provide evidence that opiate effects on the gastrointestinal tract are mediated centrally as well as peripherally.