ELSEVIER Brain Research 662 (1994) 233-239 BRAIN RESEARCH Research report Changes in monoamine turnover in forebrain areas associated with masculine sexual behavior: a microdialysis study Blas Fumero, Juan Ramdn Fernandez-Vera, Jose Luis Gonzalez-Mora, Manuel Mas * Department of Physiology, University of La Laguna, Medical School, Tenerife, Spain Accepted 9 August 1994 Abstract This report compares the changes in the main dopamine (DA) and serotonin (5-HT) metabolites, respectively dihydrox- yphenylacetic acid (DOPAC) and 5-hydroxy indoleacetic acid (5-HIAA) in three relatively close brain regions, namely he nucleus accumbens (ACB), the medial preoptic area, and the medial basal hypothalamus (MBH), as well as DA in the ACB, of copulating male rats. All these neurochemicals remained fairly stable when the animals were exposed to non sexual social stimuli (castrated females), and they increased during mating with receptive females. There were regional differences in these copulation-related changes, however, with those in the MBH being shorter-lived. There were also differences in the time-course of the changes in DOPAC and 5-HIAA the latter being slower. It is suggested that they reflect the involvement of the DA and 5-HT innervation of diencephalic structures in, respectively the appetitive and consummatory/satiation mechanisms of sexual behavior. The physiological relevance of these neurochemical changes is supported by the lack of differences between the standard measures for sexual behavior recorded before surgery and during the dialysis session. Keywords: Microdialysis; Dopamine; Dihydroxyphenylacetic acid; 5-Hydroxyindoleacetic acid; Nucleus accumbens; Medial preoptic area; Medial basal hypothalamus; Masculine sexual behavior I. Introduction The elucidation of the neurotransmitters involved in the regulation of sexual behavior has traditionally re- lied on pharmacological methods (see [4,30] for review). More recently, parallel to the development of sensitive analytical techniques, attention has been paid to the possible changes in the release and metabolism of endogenous transmitters concomitant to the display of sexual behavior and related social interactions. The initial studies were based on analyzing the content of various neurotransmitters and their metabolites pre- sent in different brain fragments excised after killing animals engaged in mating activity or exposed to sexu- ally relevant stimuli, and relating the neurochemical findings to the behavior displayed immediately before sacrifice [2,3,15,21,24,34]. * Corresponding author. Departamento de Fisiologia, Facultad de Medicina, Universidad de La Laguna, 38320 Tenerife, Spain. Fax: (34) (22) 603 529. 0006-8993/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0006-8993(94)00987-2 A seemingly more physiological approach is pro- vided by in vivo neurochemical techniques such as voltammetry and microdialysis. They have made possi- ble, in recent years, the assessment of extracellular levels of some transmitters and their metabolites in brain areas of freely behaving animals during their display of different behaviors, including mating. The monoamine neurotransmitters such as dopamine (DA) and serotonin as well as their main metabolites, respec- tively, dihydroxyphenylacetic acid (DOPAC) and 5-hy- droxyindoleacetic acid (5-HIAA) are especially suited for being monitored with these techniques. These two neurotransmitters have long been ascribed prominent roles in the control of masculine sexual behavior by a wealth of pharmacological studies [4,30]. An increased release of dopamine (DA) in the nu- cleus accumbens (ACB) of copulating male rats was first documented using in vivo voltammetry [22]. This finding has been consistently replicated by using micro- dialysis [8,10,27,28,35]. Milder increases in DA release in the ACB could also be detected with in vivo electro- chemical recordings by exposing the animals to sexually