Non-cholinergic ascending excitatory response in the cat small intestine: possible involvement of substance P.
Using an electromyographic technique, an ascending excitatory response was recorded "in vitro" in the presence of atropine in the cat small intestine up to 70 mm orally with respect to the site of repetitive transmural nerve stimulation. This non-cholinergic ascending excitatory response was characterized by an increase in the slow wave amplitude and spiking activity. This response was reversibly abolished by Tetrodotoxin (3,1 X 10(-6) M) but remained unchanged after exposure of the intestine to: Hexamethonium (4,9 X 10(-6) M) plus Tubocurarine (1,4 X 10(-5) M), Guanethidine (5 X 10(-7) to 5 X 10(-5) M), Domperidone (2,3 X 10(-7) to 2,3 X 10(-5) M), Naloxone (3 X 10(-7) to 3 X 10(-5) M), Methysergide (2,8 X 10(-7) to 2,8 X 10(-5) M), Metergoline (2,4 X 10(-5) M), Methiotepin (2,1 X 10(-5) M) and Mepyramine (2,3 X 10(-5) M). This response was unaffected by the substance P analogues, D-Pro2, D-Phe7, D-Trp9-Substance P (10(-5) M) or D-Pro2, D-Trp7-9-Substance P (10(-5) M) but was reversibly abolished after exposure of the intestine to substance P (10(-6) M). Moreover substance P still effectively abolished this response in the presence of any two of the above analogues. The results of the present study show that the non-cholinergic excitatory response elicited in the cat small intestine due to the activity of long ascending pathways probably involved substance P. The functional significance of this response is discussed.
Miolan
J P
JP
Département de Physiologie et Neurophysiologie, U.A., C.N.R.S. No 205. Faculté des Sciences St Jérôme, Marseille, France.
Niel
J P
JP
D000818:Animals; D002415:Cats; D004386:Duodenum / Q000502:physiology*; D004525:Efferent Pathways; D004576:Electromyography; D005769:Gastrointestinal Motility / Q000187:drug effects*; D013373:Substance P / Q000502:physiology*
D013373:Substance P