Deviant sexual behavior, hormones and sex-chromosomal relationship : A study in the spontaneously hypertensive rat (SHR)

Abstract: The general aim of the present thesis was to gain insight into some biological factors that influencedeviant sexual performance. Two inbred strains selectively bred (hypertension) from the same Wistarrat colony were used: the spontaneously hypertensive rat (SHR) and its normotensive progenitor theWistar Kyoto rat (WKY). The sexual behavior of the SHR males was found to differ from that of theWKY strain in several respects. Briefly, the SHR showed a lower copulatory intensity and socio-sexual approach behavior. The plasma levels of testosterone (T) and follicle stimulating hormonewere found to be higher in the SHR. T as well as estradiol were less efficient to reinstate the sexualbehavior in the castrated SHR than in the WKY male, suggesting a reduced responsiveness to gonadalhormones in the SHR. In contrast to the male copulatory behavior the heterotypical i.e., the hormoneinduced female copulatory response (lordosis) had the same magnitude in the SHR and WKY.Neonatal castration enhanced, whereas neonatal T treatment attenuated the T activated copulatorybehavior in the SHR male when tested in adulthood. The data suggest that the deviant sexual behaviorprofile in the SHR is mediated by nemoendocrine mechanisms during the neonatal period. Toevaluate a possible sex chromosome linkage as to the deviant sexual profile in the SHR a breedingexperiment was conducted. The SHR specific low sexual profile was not transferred to the F1-hybridcrossings between the SHR and WKY strains suggesting that the deviant sexual profile of the SHRmale cannot be derived exclusively from just one of the sex chromosomes. Female SHR rats wereused in analogous experiments. The results of these experiments showed that the mechanismsunderlying the deviant sexual behavior of the SHR was confined to the neuronal substrate associatedto male typical (dimorph) psychoneuroendocrine functions.It is concluded, that the deviant sexual profile of the SHR rat is likely to have a multidimensionalorigin to be sought in the combination of chromosomal and early endocrine or environmental factors.