Authors' current addresses P. J. Johnson: School of Chemical & Biomedical Sciences, Central Queensland University, Rockhampton, Queensland 4702, Australia.
Role of α2-adrenoceptors in the sympathetic inhibition of motility reflexes of guinea-pig ileum
Article first published online: 5 AUG 2004
The Journal of Physiology
Volume 534, Issue 2, pages 465–478, July 2001
How to Cite
Stebbing, M. J., Johnson, P. J., Vremec, M. A. and Bornstein, J. C. (2001), Role of α2-adrenoceptors in the sympathetic inhibition of motility reflexes of guinea-pig ileum. The Journal of Physiology, 534: 465–478. doi: 10.1111/j.1469-7793.2001.00465.x
M. A. Vremec: Ludwig Research Institute, Parkville, Victoria 3052, Australia.
- Issue published online: 5 AUG 2004
- Article first published online: 5 AUG 2004
- (Received 22 December 2000; accepted after revision 13 March 2001)
- 1Sympathetic regulation of the motility of guinea-pig ileum was investigated using mesenteric nerve (MN) stimulation to inhibit motility reflexes, in vitro.
- 2Transmural electrical stimulation (5 Hz, 1 s) in intact intestinal segments, or inflation of a balloon against the mucosa in opened segments, evoked contractions of the circular and longitudinal muscles oral to the stimulus.
- 3MN stimulation (10 Hz, 5 s) usually abolished contractions of the longitudinal and circular muscles evoked by either electrical or mechanical stimuli.
- 4The inhibition was mimicked by UK14,304 (70-100 nm) and abolished by idazoxan (100 nm), revealing an enhancement of circular muscle contractions. There was no evidence for α2-receptors on the muscle, suggesting sympathetic inhibition was via the myenteric plexus.
- 5Possible sites of action of noradrenaline released from sympathetic nerves were investigated using intracellular recordings from the circular muscle in a multichambered organ bath.
- 6When in the stimulation chamber, UK14,304 depressed (by 50 %) excitatory junction potentials (EJPs) recorded oral to a distension stimulus, but did not affect inhibitory junction potentials (IJPs) recorded anal to the stimulus. When added to a chamber between the stimulus and recording chambers, UK14,304 depressed EJPs by 40 %, but did not alter IJPs. When in the recording chamber, UK14,304 depressed EJPs by 20 %, but had no effect on IJPs. IJPs were inhibited, however, when UK14,304 was applied to the whole bath.
- 7It is concluded that sympathetic activity inhibits intestinal motility mainly via α2-adrenoceptors on ascending interneurons and intrinsic sensory neurons of the orally directed reflex pathway.