The Psychophysiology of Sex

Neuroendocrine Processes during Sexual Arousal and Orgasm

Neuroendocrine Processes during Sexual Arousal and Orgasm tillmann h. c. krüger, manfred schedlowski, and michael s. exton Neuroendocrine Response to Acute Sexual Arousal Despite investigation now spanning well over 30 years, little consensus has been reached regarding the endocrine control of sexual arousal in healthy humans. Historically, the approach to this question has been to measure the endocrine response to various modes of sexual stimulation. This undertaking allows an examination of hormones that may be involved in the up- or down-regulation of a sexual response, depending on the timing and magnitude of such changes. Numerous studies conducted during the past three decades have shown a high level of agreement in regard to cardiovascular responses to sexual activity (Carmichael, Warburton, Dixen, & Davidson, 1994; Littler, Honour, & Sleight, 1974; Nemec, Mans¤eld, & Kennedy, 1976; Whipple, Ogden, & Komisaruk, 1992). In contrast, studies that examined the responses of sympathetic, pituitary, and gonadal hormones have been notable for lack of consistency in their conclusions (Blaicher et al., 1999; Brown & Heninger, 1975; Carani et al., 1990; Carmichael et al., 1994, pp. 10–20; Fox, Ismail, Love, Kirkham, & Loraine, 1972; Heiman , Rowland, Hatch, & Gladue, 1991; La Ferla, Anderson, & Schalch, 1978; Lee, Jaffe, & Midgley, 1974; Levi, 1969; Lincoln, 1974; Pirke, Kockott , & Dittmar, 1974; Purvis, Landgren, Cekan, & Diczfalusy, 1976; Rowland et al., 1987; Stoléru, Ennaji, Counot, & Spira, 1993; Wiedeking, Lake, Ziegler, Kowarski, & Money, 1977). Nevertheless, we must be cognizant that technical advances, combined with the use of a number of very different methodological approaches, contribute signi¤cantly to the variance between or differences in the data from different experiments. Inconsistent Methodology Studies examining the neuroendocrine response to sexual arousal and orgasm have employed a number of different methodologies, thus making general interpretations dif¤cult. One potential confound involves the differences in the methods employed for the induction of sexual arousal. Researchers have employed the viewing of stimulating ¤lms, imagery of fantasies , masturbation, and coitus. These methods clearly demonstrate different 83 characteristics of sexual stimulation, with differences in duration and intensity of exposure, as well as the amount of physical contact. Additionally, differences between such studies are further compounded by some studies requesting participants to achieve orgasm, while others did not. Together, such factors have contributed to the inability to directly compare data generated from different laboratories. Additionally, a primary concern limiting the evaluation of results from these studies is the method of blood collection. Blood has often been sampled at single discrete time points, sometimes with the experimenter entering the experimental room. Such a methodology has a number of potential de¤cits. Firstly, short-term alterations of certain neuroendocrine variables may be missed by using this technique. Secondly, entering the experimental room may cause the participant undue concern, which may potentially contribute to any observed endocrine alterations. Thirdly, punctual blood sampling may induce physical discomfort that also may impact hormonal status. Therefore, we designed a method for the examination of the neuroendocrine response to sexual arousal and orgasm in healthy males and females (Exton et al., 1999; Exton, Krüger, Bursch, et al., 2001; Exton, Krüger, Koch, et al., 2001; Exton et al., 2000; Krüger et al., 1998). We established this paradigm so as to eliminate dif¤culties due to punctual blood sampling, as well as the in®uence of the presence of the experimenter . By keeping these factors constant, we are able to compare factors that are incomparable in the existing literature—namely the effect of different modes of stimulation, as well as the in®uence of orgasm on endocrine alterations following sexual arousal. Improved Methodology For the examination of the endocrine response to sexual arousal and orgasm, we developed a laboratory model of continuous blood sampling that we formerly established in experimental ¤eld studies. Most experiments were conducted in 10 healthy male or female volunteers. Each experiment was conducted in participants naive to the experimental conditions . All subjects were exclusively heterosexual and reported a relaxed attitude toward masturbation and pornography. All volunteers underwent an intensive nonstructured clinical interview to exclude men and women with confounding physical or mental health problems (e.g., drug or alcohol abuse, medication intake, or sexual dysfunctions). Volunteers were requested to refrain from any kind of sexual activity and to avoid alcoholic beverages or other drugs 24 hours prior to the laboratory investigation. The study paradigm is displayed in Figure 1. A balanced crossover design was implemented, involving two sessions on consecutive days, with each session commencing in the afternoon (at 3 p.m.). Subjects lay down on a comfortable bed...