Pharmacological Profiles of Muscarinic Receptors in the Longitudinal Smooth Muscle of Guinea Pig Ileum

Abstract

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 NK,-receptor antagonists, spantide and L-668,169, and a selective NK2-recep tor 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 NK, 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 NK,-receptor subtypes, spantide and L-668,169 an tagonized 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 rab bit iris sphincter preparation is mediated by NK,-receptors which are activated by endogenously released NKA.

Effects of RP 67580, a tachykinin NK1 receptor antagonist, on a primary afferent‐evoked response of ventral roots in the neonatal rat spinal cord

“…These results suggest that NKA acts on NK1 rather than NK2 receptors in the neonatal rat spinal cord. The possibility that NKA acts on NK1 receptors has also been suggested in other preparations (Kunitomo et al, 1993;Zhao et al, 1993).…”

Neurokinin A Is a Main Constituent of Sensory Neurons Innervating the Anterior Segment of the Eye

“…The prominent innervation of the iris sphincter muscle is of relevance, as NKA has been shown to contract this muscle in the rat, 35 rabbit, 36 -41 and pig 42 via activation of NK-1 receptors, at least in the rabbit. 41 Miosis induced by peptides deriving from the TG is well known to occur in response to topical noxious stimulation in lower mammals and has been shown to be mainly mediated by SP (see review, see Ref. 43).…”

TLR2 and TLR4 Modulate Mouse Ileal Motility by the Interaction with Muscarinic and Nicotinic Receptors

“…To address the role of the muscarinic and nicotinic ACh receptors on the responses triggered by ACh, the ileum sections were incubated for 15 min with 0.2 µM AF-DX 116, a selective muscarinic acetylcholine receptor (mAChR) M2 antagonist; 0.1 µM 4-DAMP, a specific mAChR M3 antagonist; 10 µM mecamylamine, non-selective nicotinic acetylcholine receptors (nAChR) α3 and β4 antagonists; or 2 nM α-bungarotoxin, a specific α7 nicotinic acetylcholine receptor (nAChR) antagonist, prior to the performance of the 0.1–10 µM ACh concentration–response curves. Previous studies have reported that similar concentration ranges of these antagonists induce effects in the neurotransmission of the intestinal smooth muscle [ 24 , 26 , 27 ].…”