Summary
Clonidine (0.2 mg/kg i.v.) and St 587 (1 mg/kg i.v.), selective agonsists ofα 2- andα 1-adrenoceptors, respectively, increased the flexor reflex amplitude in the spinal rat. Yohimbine and rauwolscine,α 2-adrenoceptor antagonists, inhibited dose-dependently the effect of clonidine but not of St 587. However, prazosin and clozapine,α 1-adrenoceptor antagonists, diminished the action of both agonists in a dose-dependent manner. After central chemosympathectomy caused by 6-OH-DA or DSP-4 the response to clonidine did not differ from that in the sham-operated animals. In 6-OH-DA treated rats yohimbine (1 mg/kg i.v.) antagonized the effect of clonidine to the same extent as it did in unlesioned animals. It is concluded that the results are functional evidence thatα 1- andα 2-adrenoceptors are present in the rat spinal cord, and stimulation of each receptor increases flexor reflex activity.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Andén N-E, Jukes MGM, Lundberg A (1966) The effect of DOPA on the spinal cord. Acta Physiol Scand 67: 387–397
Andén N-E (1970) Effects of amphetamine and some other drugs on central catecholamine mechanisms. In: Costa E, Garattini S (eds) Symposium on amphetamines and related compounds. North-Holland Publ Co, Amsterdam, pp 447–462
Andén N-E, Corrodi M, Fuxe K, Hökfelt T, Rydin C, Svensson T (1970) Evidence for a central noradrenaline receptor stimulation by clonidine. Life Sci 9, Part I: 513–523
Andén N-E, Grabowska M, Strömbom U (1976) Different alpha-adrenoceptors in the central nervous system mediating biochemical and functional effects of clonidine and receptor blocking agents. Naunyn-Schmiedebergs Arch Pharmacol 292: 43–52
Astrachan DI, Davis M, Gallager DW (1983) Behavior and binding: correlation betweenα 2-adrenergic stimulation of acoustic startle andα 1-adrenoceptor occupancy and number in rat lumbar spinal cord. Brain Res 260: 81–90
Austin JH, Nygren LG, Fuxe K (1976) A system for measuring the noradrenaline receptor contribution of the flexor reflex. Med Biol 54: 352–363
Cambridge D (1981) UK-14, 304, a potent and selectiveα 2-agonist for the characterization ofα-adrenoceptor subtypes. Eur J Pharmacol 72: 413–415
Carlsson A, Magnusson T, Rosengren E (1963) 5-Hydroxytryptamine of the spinal cord normally and after transection. Experimentia (Basel) 19: 359
Cavero I, Roach AG (1980) The pharmacology of prazosin, a novel antihypertensive agent. Life Sci 27: 1525–1540
De Jonge A, van Meel JCA, Timmermans PBMWM, van Zwieten PA (1981) A lipophylic, selectiveα 1-adrenoceptor agonist: 2-(2-chloro-5-trifluoro-methylphenylimino)imidazoline (St 587). Life Sci 28: 2009–2016
Earley CJ, Leonard BE (1978) Isolation and assay of noradrenaline, dopamine, 5-hydroxy-tryptamine, and several metabolites from brain tissue using disposable Bio-Rad columns packed with Sephadex G-10. J Pharmacol Methods 1: 67–79
Ferry N, Goodhardt M, Hanoune J, Sevenet T (1983) Binding of yohimbine stereoisomers toα-adrenoceptors in rat liver and human platelets. Br J Pharmacol 78: 359–364
Jones DJ, Kendall DE, Enna SJ (1982) Adrenergic receptors in rat spinal cord. Neuropharmacology 21: 191–195
Jonsson G, Hallman H, Ponzio F, Ross S (1981) DSP-4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine] — a useful denervation tool for central and peripheral noradrenaline neurons. Eur J Pharmacol 72: 173–188
Keller H, Bartholini E, Pletscher A (1973) Increase of 3-methoxy-4-hydroxy-phenylethylene glycol in rat brain by neuroleptic drugs. Eur J Pharmacol 23: 183–186
Kobinger W, Pichler L (1983) Subgroups ofα-adrenoceptors: selectivity of drugs and receptor importance in various target system. In: Bock KD (ed) Catapresan (Clonidin) Wege der Entwicklung eines Pharmakons. Editio Cantor, Aulendorf, pp 83–91
Langer SZ, Shepperson NB (1982) Recent developments in vascular smooth muscle pharmacology: the post-synapticα 2-adrenoceptor. Trends Pharmacol Sci 3: 440–444
Maj J, Palider W, Baran L (1976) The effects of serotonergic and antiserotonergic drugs on the flexor reflex of spinal rat: a proposed model to evaluate the action of the central serotonin receptor. J Neural Transm 38: 131–147
Maj J, Görka Z, Melzacka M, Rawłów A, Pilc A (1983) Chronic treatment with imipramine: further functional evidence for the enhanced noradrenergic transmission in flexor reflex activity. Naunyn-Schmiedebergs Arch Pharmacol 322: 256–260
Nozaki M, Bell JA, Martin WR (1980) Noradrenergic action of amphetamine following degeneration of descending monoaminergic fibers in the spinal cord. Psychopharmacology 67: 25–29
Nygren L-G, Olson L (1976) On spinal noradrenaline receptor supersensitivity: correlation between nerve terminal densities and flexor reflexes various times after intracisternal 6-hydroxydopamine. Brain Res 116: 455–470
Palider W, Rawłów A (1977) Effect of serotonin uptake blocking agents on the flexor reflex of hind limb of the spinal rat. Pol J Pharmacol Pharm 29: 367–376
Pawłowski L, Ruczynska J, Maj J (1980 a) Zimelidine and clomipramine: different influence on the fenfluramine but not p-chloroamphetamine-induced pharmacological effects. Neurosci Lett 16: 203–207
Pawłowski L, Ruczynska J, Przegalinski E (1980 b) The effect of thyroliberin and some of its analogues on the hind limb flexor reflex in the spinal rat. Pol J Pharmacol. Pharm 32: 539–550
Pawłowski L, Roǵoz Z, Skuza G, Maj J (1982) Central effects of St 587 [2-(2-chloro-5-trifluoromethylphenylimino)imidazolidine], a new alpha1, adrenoceptor agonist. In: Abstracts of 13th CINP Congress, Jerusalem, June 20–25
Przegalinski E, Bigajska K, Lewandowska A (1981) The influence of rolipram on the central serotoninergic system. Pharmacopsychiatria 14: 162–166
Przegalinski E, Rawłów A (1982) The stimulatory action of phosphodiesterase inhibitors on the flexor reflex of the hind limb in the spinal rat. J Neural Transm 55: 9–17
van Meel JCA, De Jonge A, Timmermans PBMWM, van Zwieten PA (1981) Selectivity of some alpha-adrenoceptor agonists for peripheral alpha1- and alpha2-adrenoceptors in the normotensive rat. J Pharmacol Exp Ther 219: 760–767
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Rawłów, A., Górka, Z. Involvement of postsynaptic α1- and α2-adrenoceptors in the flexor reflex activity in the spinal Rats. J. Neural Transmission 66, 93–105 (1986). https://doi.org/10.1007/BF01260905
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF01260905