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Involvement of substance P present in primary afferent neurones in modulation of cutaneous blood flow in the instep of rat hind paw
Author(s) -
Yonehara Norifumi,
Chen JiQiang,
Imai Yasuo,
Inoki Reizo
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14325.x
Subject(s) - antidromic , chemistry , sciatic nerve , stimulation , substance p , endocrinology , medicine , methysergide , phentolamine , neurogenic inflammation , anesthesia , antagonist , neuropeptide , receptor , biochemistry
1 The participation of small‐diameter afferent fibres in the microcirculatory haemodynamics of cutaneous tissue was examined by studies on the effects of antidromic stimulation of primary afferent neurones on cutaneous blood flow (CBF) and tachykinin release into the subcutaneous space in the instep of the hind paw of rats. 2 Antidromic stimulation of the sectioned sciatic nerve induced a biphasic flow response, an initial transient decrease followed by an increase, with no alteration in the blood pressure. 3 Neither phase was affected by pretreatment with phentolamine (0.1 mg kg −1 , i.a.), propranolol (0.5 mg kg −1 , i.a.), atropine (0.5 mg kg −1 , i.a.), methysergide (0.5 mg kg −1 , i.a.) or mepyramine (10 mg kg −1 , i.a.) plus cimetidine (10 mg kg −1 , i.a.), but both were significantly inhibited by pretreatment with capsaicin (50 mg kg −1 , s.c). 4 Spantide (1–2 μmol kg −1 , i.a.), a substance P (SP) antagonist, reduced the basal CBF, and also inhibited both phases of the biphasic flow response evoked by antidromic stimulation of the sectioned sciatic nerve. 5 Intra‐arterial infusion of SP (0.5 μmol kg −1 , i.a.) induced a biphasic flow response similar to that elicited by antidromic stimulation of the sectioned sciatic nerve. 6 Antidromic stimulation of the sectioned sciatic nerve caused a marked increase in SP release into the subcutaneous perfusate of the instep of the rat hind paw, but no detectable increase in neurokinin A release. 7 We suggest that SP and its receptors are mainly responsible for the vascular response induced by stimulation of the sectioned sciatic nerve, and that small‐diameter afferent fibres containing SP tonically regulate vascular tone in cutaneous microvessels.