Individual differences in male rat ejaculatory behaviour: searching for models to study ejaculation disorders

Abstract

In addition to investigating sexual function in rats that display normal ejaculatory behaviour, studying rats that are either 'hyposexual' or 'hypersexual' may provide important insights into the aetiology of ejaculatory dysfunctions in men, such as premature and retarded ejaculation. To this end, rats were matched into groups of 'sluggish', 'normal' and 'rapid' ejaculators based on their ejaculation frequencies displayed in a series of weekly sexual behaviour tests. Selecting rats on this parameter revealed large and stable differences in other parameters of sexual behaviour as well, including ejaculation latency and mount frequency but not intromission frequency and mount latency, putative indices of sexual motivation. Neuroanatomically, Fos immunoreactivity as a measure of neuronal activation was increased in rapid ejaculators compared with sluggish ejaculators in ejaculation-related brain areas, presumably associated with the differences in ejaculatory behaviour. Although the total number of oxytocin neurones within subregions of the hypothalamus did not differ between groups, in the supraoptic nucleus of the hypothalamus more oxytocin neurones were activated in rapid ejaculators compared with the other groups. Apart from the differences observed in ejaculatory behaviour, groups did not differ with respect to their locomotor activity and approach-avoidance behaviour as measured in the elevated plus-maze. Finally, apomorphine-induced stereotypy was similar in sluggish and rapid ejaculators, suggesting no large differences in dopamine susceptibility. Altogether, the present results suggest stable differences in male rat ejaculatory behaviour. Further exploring the neurobiological mechanisms underlying these differences may be a promising approach to gain insights into the aetiology of sexual dysfunctions such as premature, retarded or an-ejaculation.

Functional and Psychological Characteristics of Belgian Men with Premature Ejaculation and Their Partners

“…More specifically, drugs stimulating the 5-HT2c receptors appear to delay ejaculation, while those stimulating the 5-HT2a receptors accelerate it. Dopaminergic neurons probably also intervene (Peeters & Giuliano, 2008) and research has been conducted which supports the involvement of some oxytocin receptors (Pattij et al, 2005). The sensitivity of these neurophysiological systems varies from one individual to another, depending notably on genetic factors.…”

Sexual Dysfunction, Depression and Antidepressants: A Translational Approach

“…Some rats were sexually very active, some not at all and the rest with a variety of intermediate levels [25]. We standardly test all males subsequently for four weekly tests of 30 minutes, which generates very stable levels of sexual behavior in individual males.…”

Relationship of delay aversion and response inhibition to extinction learning, aggression, and sexual behaviour

“…The sexual behaviour procedure was adapted from Pattij et al [37]. After the extinction test, the male animals were housed apart from each other and a companion female was introduced (see Section 2.1).…”