title: Pharmacological analysis of receptors involved in the late, tachykininergic contractile response to electrical transmural stimulation in isolated rabbit iris sphincter muscle.
abstract: We characterized the pharmacological nature of the tachykinin receptor subtype mediating the contractile response to electrical transmural stimulation (ETS) in the isolated rabbit iris sphincter muscle preparation by using selective NK1-receptor antagonists, spantide and L-668,169, and a selective NK2-receptor antagonist, L-659,877. ETS caused a biphasic contraction in this preparation: a rapidly developing cholinergic component followed by a slowly decaying tachykininergic component. The tachykininergic contractile response to ETS was effectively attenuated by spantide and L-668,169, but only slightly by L-659,877, indicating that the tachykinin receptors mediating ETS-induced contraction are of the NK1 type. In the same preparation, the contractile activity of substance P (SP) was slightly more potent than that of neurokinin A (NKA). Unlike in other tissues rich in NK1-receptor subtypes, spantide and L-668,169 antagonized the contractile response to NKA more effectively than that to SP, and the reverse was observed for L-659,877. These results strongly suggest that the tachykininergic contraction induced by ETS in the rabbit iris sphincter preparation is mediated by NK1-receptors which are activated by endogenously released NKA.
authors.affiliation: Department of Pharmacology, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kunitomo
authors.forename: N
authors.initials: N
authors.lastname: Imaizumi
authors.forename: E
authors.initials: E
authors.lastname: Sameshima
authors.forename: M
authors.initials: M
authors.lastname: Fujiwara
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D007498:Iris / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D011817:Rabbits; D018039:Receptors, Tachykinin / Q000187:drug effects / Q000502:physiology*; D013373:Substance P / Q000031:analogs & derivatives* / Q000494:pharmacology; D015320:Tachykinins / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D010456:Peptides, Cyclic; D018039:Receptors, Tachykinin; D015320:Tachykinins; C076509:L 668169; D013373:Substance P; C042867:spantide