Hormones, genes and the structure of sexual arousal

Despite the inherent difficulty of connecting individual genes with integra ted mammalian behaviors, it has been determined that a series of genes are turned on by estrogenic hormones acting in forebrain. Their products are, i n turn, facilitatory for female reproductive behaviors such as lordosis. Th e causal routes by which two genes contribute to the control of lordosis be havior, the classical estrogen receptor gene (ER-alpha) and a thyroid hormo ne (TH) receptor gene (TR-beta), have been delineated. Beyond the mechanism s underlying the expression of concrete, specific natural behaviors, lies t he question of sexual motivation. Required as an intervening variable to ex plain fluctuations in natural behaviors in the face of constant stimuli? mo tivational states have both general and specific features. Most theoretical and experimental approaches toward the general aspects of motivation have depended heavily on concepts of 'arousal.' Sexual arousal is likely to depe nd both on very general, broadly distributed neuronal influences and on spe cific affiliative and sexual tendencies. Is 'general arousal' a monolithic, undifferentiated process? In no way can a review at this time settle such issues, but the reasons behind six new experimental approaches to these que stions are described. (C) 1999 Elsevier Science B.V. All rights reserved.