Summary
Intravenous administration of catecholamines produced dose-related inhibition of electrodermal responses (EDRs) evoked by electrical stimulation of the post-ganglionic sciatic nerve in anaesthetized rats, with relative potencies being (−)-adrenaline > (±)-adrenaline > (−)-noradrenaline = (+)-adrenaline. The suppression of EDRs by (±)-adrenaline and (−)-noradrenaline was blocked by pretreatment with yohimbine (0.75 mg/kg i.v.) but not by prazosin (0.3 mg/kg i. v.). The selective α2-adrenoceptor agonist B-HT 920 also inhibited neurally evoked skin potential responses. This effect of B-HT 920 was antagonized by the selective α2-adrenoceptor antagonist idazoxan (0.1 mg/kg i. v.) but was insensitive to prazosin. Idazoxan was more potent than yohimbine in blocking (±)-adrenaline-induced suppression of EDRs. Methacholine administered into the femoral artery evoked EDRs by an atropine-sensitive mechanism. Methacholine-induced EDRs were not suppressed by intravenous administration of (−)-adrenaline (1 μg/kg or 3 μg/ kg) whereas EDRs evoked by the sciatic nerve stimulation on the other hindpaw were inhibited. Increase in the endogenous catecholamines by asphyxia strongly inhibited EDRs by a mechanism which was also sensitive to yohimbine but not to prazosin. These results suggest that peripheral presynaptic α2-adrenergic mechanisms are involved in inhibition of transmitter release in this sympatheticcholinergic system.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Ahlquist RP (1948) A study of the adrenotropic receptors. Am J Physiol 153:586–600
Bennett DR, Reinke DA, Alpert E, Baum T, Vasquez-Leon H(1961) The action of intraocularly administered adrenergic drugs on the iris. J Pharmacol Exp Ther 134:190–198
Billigheimer E (1920) Über einen Antagonismus zwischen Pilokarpin und Adrenalin. Naunyn-Schmiedeberg's Arch Exp Path Pharmak 88:172–178
Chapleo CB, Doxey JC, Myers PL, Roach AG (1981) RX 781094, a new potent, selective antagonist of α2-adrenoceptors. Br J Pharmacol 74:842p
Darrow CW (1937) Neural mechanisms controlling the palmar galvanic skin reflex and palmar sweating. Arch Neurol Psychia (Chic) 37:641–663
Davison MA, Koss MC (1975) Brainstem loci for activation of electrodermal response in the cat. Am J Physiol 229:930–934
Doxey JC, Gadie B, Lane AC, Tulloch IF (1983) Evidence for pharmacological similarity between α2-adrenoceptors in the vas deferens and central nervous system of the rat. Br J Pharmacol 80:155–161
Doxey JC, Lane AC, Roach AG, Virdee NK (1984) Comparison of the α-adrenoceptor antagonist profiles of idazoxan (RX 781094), yohimbine, rauwolscine and corynanthine. Naunyn-Schmiedeberg's Arch Pharmacol 325:136–144
Gherezghiher T, Koss MC (1985) Ocular effects of adrenergic stereoisomers in the rabbit. J Ocular Pharmacol 1:19–28
Girardot MN, Koss MC (1984) A physiological and pharmacological analysis of the electrodermal response in the rat. Eur J Pharmacol 98:185–191
Grundstrom N, Andersson RGG, Wikberg JES (1981) Prejunctional alpha2-adrenoceptors inhibit contraction of tracheal smooth muscle by inhibiting cholinergic neurotransmission. Life Sci 28:2981–2986
Kobinger W, Pichler L (1981) α1- and α2-Adrenoceptor subtypes: selectivity of various agonists and relative distribution of receptors as determined in rats. Eur J Pharmacol 73:313–321
Koss MC, Davison MA (1976) The electrodermal response as a model for central sympathetic reactivity: the action of clonidine. Eur J Pharmacol 37:71–78
Koss MC, Davison MA, Bernthal PJ (1976) Epinephrine inhibition of the electrodermal response in the cat. Psychopharmacol 50:149–152
Rhodes KF, Waterfall JF (1987) The effects of some α-adrenoceptor antagonists on the response of the canine saphenous vein to BHT 933, UK-14304 and methoxamine. Naunyn-Schmiedeberg's Arch Pharmacol 335:261–268
Sato K (1977) The physiology, pharmacology and biochemistry of the eccrine sweat gland. Rev Physiol Biochem Pharmacol 79:51–131
Starke K (1981) α-Adrenoceptor subclassification. Rev Physiol Biochem Pharmacol 88:198–236
Starke K, Docherty JR (1981) Alpha1- and alpha2-adrenoceptors: pharmacology and clinical implications. J Cardiovasc Pharmacol 3 (suppl 1):S14-S23
Timmermans PBMWM, van Zwieten PA (1982) α2-Adrenoceptors: classification, localization, mechanisms and targets for drugs. J Med Chem 25:1389–1401
Trendelenburg U (1965) Supersensitivity by cocaine to dextrorotatory isomers of norepinephrine and epinephrine. J Pharmacol Exp Ther 148:329–338
Walland A (1984) Clonidine inhibits electrodermal potentials induced by preganglionic stimulation. Eur J Pharmacol 102:47–53
Wang GH (1957) The galvanic skin reflex. A review of old and recent works from a physiologic point of view. Part one. Am J Physiol Med 36:295–320
Wang GH (1958) The galvanic skin reflex. A review of old and recent works from a physiologic point of view. Part two. Am J Physiol Med 37:35–57
Wikberg JES (1979) The pharmacological classification of adrenergic α1 and α2 receptors and their mechanisms of action. Acta Physiol Scand 106 (suppl 468):1–99
Author information
Authors and Affiliations
Additional information
Send offprint requests to M. C. Koss
Rights and permissions
About this article
Cite this article
Ito, T., Koss, M.C. Inhibition of a peripheral sympathetic-cholinergic system by presynaptic α2-adrenoceptors. Naunyn-Schmiedeberg's Arch Pharmacol 337, 24–28 (1988). https://doi.org/10.1007/BF00169472
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00169472