A pharmacological and immunohistochemical study of the splanchnic innervation of ileal longitudinal muscle in the toad Bufo marinus.
A study was made of the innervation of the longitudinal muscle of the toad ileum with particular emphasis on the splanchnic innervation by non-adrenergic, non-cholinergic (NANC) nerves. Nerve fibres containing substance P-like immunoreactivity (SP-LI) were observed in the gut wall and in the ileal wall after degenerative section of the splanchnic nerves. Incubation overnight in a high concentration of capsaicin (3 X 10(-4) M) caused degeneration of SP-LI fibres. No evidence was obtained for enteric neurons containing SP-LI. Substance P caused a contraction of the longitudinal muscle similar to that produced by nerve stimulation. The response to nerve stimulation was decreased by about 60% by treatment with alpha-chymotrypsin. Capsaicin normally evoked a contraction of the longitudinal muscle, but did not do so after degenerative section of the splanchnic nerves. Prolonged treatments with high concentrations of capsaicin (5 X 10(-5) M) abolished the excitatory response to nerve stimulation. The results suggest that substance P is the transmitter mediating the NANC contraction. The fibres releasing the transmitter are possibly antidromically activated, sensory afferents. Both transmural stimulation and capsaicin caused a NANC inhibition of longitudinal muscle. Stimulation of perivascular nerves after splanchnic nerve section caused a NANC excitation, as did transmural stimulation even after nerve section or capsaicin treatment.
D000818:Animals; D002024:Bufo marinus; D002211:Capsaicin / Q000494:pharmacology; D002918:Chymotrypsin / Q000494:pharmacology; D003714:Denervation; D005260:Female; D007082:Ileum / Q000187:drug effects / Q000294:innervation*; D007158:Immunologic Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009412:Nerve Fibers / Q000032:analysis / Q000502:physiology; D013153:Splanchnic Nerves / Q000502:physiology; D013373:Substance P / Q000032:analysis / Q000494:pharmacology*
D013373:Substance P; D002918:Chymotrypsin; D002211:Capsaicin