Data issued from morphological and physiological experiments suggests that the noradrenergic system, through ascending pathways to the brain and descending pathways to the spinal cord, may regulate male sexual functions. Adrenoceptors have been shown to be present in the brain and spinal cord of animals and humans. The activity of spinal preganglionic neurons is modulated by noradrenaline. Pharmacological approaches aiming at selectively targeting α1- or α2-adrenoceptors have been conducted in patients with erectile dysfunction or in monkeys and rats in a variety of tests. Briefly, conclusions arising from these studies are: activation of α1-adrenoceptors facilitates copulation, where activation of α2-adrenoceptors inhibits copulation. α2-adrenoceptors antagonists like yohimbine facilitate sexual behavior, reducing ejaculation latency in male rats and increasing their sexual motivation. Furthermore, yohimbine induces copulation in rats either castrated or sexually naive. In contrast, activation of α1-adrenoceptors depresses sexual responses in another context, i.e. reflexive erections. Activation of α2-adrenoceptors activates reflexive erections in rats, and α2-adrenoceptors antagonists (yohimbine) inhibit them. Today’s challenge is to separate the effects of any drug acting at the level of the α-adrenoceptors on the central vs. peripheral control of sexual functions, on the brain vs. spinal cord control of the same functions, and the search for any specialization of α-adrenoceptors subtypes in a given sexual function. Treatment of sexual dysfunctions in man (e.g. ejaculation) focusing on the spinal cord as a pharmacological target should also be expanded. Finally, considering the similarities between neural networks controlling male and female sexual functions, the treatment of female sexual dysfunction with comparable pharmacological approaches should be evaluated.

Aston-Jones G, Shipley MT, Grzanna R: The locus coeruleus, A5 and A7 noradrenergic cell groups. In: Paxinos (Eds), The Rat Nervous System, second edition 1995, pp 183–213.
Clark JT, Smith ER and Davidson JM: Enhancement of sexual motivation in male rats by yohimbine. Science 1984;225:847–849.
Clark JT, Smith ER and Davidson JM: Evidence for the modulation of sexual behavior by alpha-adrenoceptors in male rats. Neuroendocrinology 1985;41:36–43.
Clark JT and Smith ER: Clonidine suppresses copulatory behavior and erectile reflexes in male rats: lack of effect of naloxone pretreatment. Neuroendocrinology 1990;51:357–364.
Clark JT: Suppression of copulatory behavior in male rats following central administration of clonidine. Neuropharmacology 1991;30:373–382.
Hernandez-Gonzalez M, Oropeza MV, Guevara MA, Cervantes M, Morali G: Effects of intrathecal administration of adrenergic agonists on the frequency of copulatory pelvic thrusting of the male rat. Arch. Med. Res., 1994;25:419–425.
Smith ER, Lee RL, Schnur SL and Davidson JM: Alpha 2-adrenoceptor antagonists and male sexual behavior: II. Erectile and ejaculatory reflexes. Physiol. Behav. 1987;41:15–19.
Roussel B, Pujol JF and Jouvet M: Effects of lesions in the pontine tegmentum on the sleep stages in the rat. Arch. Ital Biol 1976;114:188–209.
Bancroft J: Are the effects of androgens on male sexuality noradrenergically mediated? Some consideration of the human. Neurosci. Biobehav Rev 1995;19:325–330.
Day HE, Campeau S, Watson SJ Jr and Akil H: Distribution of alpha 1a-, alpha 1b- and alpha 1d-adrenergic receptor mRNA in the rat brain and spinal cord. J. Chem. Neuroanat. 1997;13:115–139.
Roudet C, Mouchet P, Feuerstein C and Savasta M: Normal distribution of alpha 2-adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: a quantitative autoradiographic study. J. Neurosci. Res 1994;39:319–329.
Roudet C, Gimenez-Ribotta M, Privat A, Feuerstein C and Savasta M: Regional study of spinal alpha 2-adrenoceptor densities after intraspinal noradrenergic-rich implants on adult rats bearing complete spinal cord transection or selective chemical noradrenergic denervation. Neurosci. Lett. 1996;208:89–92.
Young WS and Kuhar MJ: Noradrenergic alpha 1 and alpha 2 receptors: Light microscopic autoradiographic localisation. Proc. Natl. Acad. Sci. USA 1980;77:1696–1700.
Wada T, Otsu T, Hasegawa Y, Mizuchi A and Ono H: Characterization of alpha 1-adrenoceptor subtypes in rat spinal cord. Eur. J. Pharmacol. 1996;312:263–266.
Danuser H and Thor KB: Inhibition of central sympathetic and somatic outflow to the lower urinary tract of the cat by the alpha 1 adrenergic receptor antagonist prazosin. J. Urol. 1995;153:1308–1312.
Downie JW and Bialik GJ: Evidence for a spinal site of action of clonidine on somatic and viscerosomatic reflex activity evoked on the pudendal nerve in cats. J. Pharmacol. Exp. Ther. 1988;246:352–358.
Gajewski J, Downie JW and Awad SA: Experimental evidence for a central nervous system site of action in the effect of alpha-adrenergic blockers on the external urinary sphincter. J. Urol. 1984;132:403–409.
Becker AJ, Stief CG, Machtens S, Schultheiss D, Hartmann U, Truss MC, Jonas U: Oral phentolamine as treatment for erectile dysfunction. J Urol 1998;159:1214–1216.
Ernst E, Pittler MH: Yohimbine for erectile dysfunction: a systematic review and meta-analysis of randomized clinical trials. J Urol. 1998;159:433–436.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.