Sexual response arousal

From a simple psychopharmacological perspective, the human sexual response can be divided into three phases, each with distinct and relatively nonoverlapping neurotransmitter functions, namely, libido, arousal, and orgasm. 

FIGURE 14—2. Psychopharmacology of the human sexual response, part 2. Sexual arousal in peripheral genitalia is accompanied by erections in men and lubrication and swelling in women. Both nitric oxide and acetylcholine mediate these actions. 

In summary, there are three major psychopharmacological stages of the human sexual response (Fig. 14—7). Multiple neurotransmitters mediate these stages, but only some of them are understood. Libido (stage 1) has dopaminergic dimensions to its pharmacology. The mechanism of arousal (stage 2), which is characterized by... 

In this chapter, issues in psychopharmacology related to sex and sexuality were discussed. This included an overview of the neurotransmitter mechanisms involved in the three psychopharmacological stages of the human sexual response, namely libido, arousal, and orgasm. Neurotransmitters that mediate each of these three stages were discussed, as well as drugs that facilitate and inhibit these stages. A specific introduction to the nitric oxide neurotransmitter system was outlined. 

To explore the psychopharmacology of the human sexual response, including libido, arousal and orgasm. 

A reasonable conclusion, about the acute effects of alcohol on male sexual response is that, similar to aggression, the disinhibition theory falls far short of explaining the information that is available. Rather, social and psychological factors seem to be important determinants of sexual response in men at low BACs and often work to increase libido. However, the pharmacology of alcohol begins to dominate at BACs greater than 0.05%, which cause a decrease in arousal and sexual competence. 

The midbrain (mesencephalon) is the top of the brain stem. The dorsal midbrain is the tectum, which is involved in eye movements and reflexive reactions to sensory stimuli. The mesencephalic reticular formation projects upward to the forebrain and is involved in arousal and attention. The periaqueductal gray area surrounds the cerebral aqueduct, and integrates analgesic, defensive/aggressive, sexual, and autonomic responses. The red nucleus and substantia nigra are important structures in motor function. 

Khat produces effects similar to those of other monoamine stimulants, (i.e., increases in mental stimulation, physical endurance, elevated mood) (Widler etal. 1994 Kalix 1994 Brenneisen etal. 1990). Stimulus generalization occurs between cathinone, amphetamine, and cocaine, suggesting similar subjective effects (Huang and Wilson 1986). Similar to other monoamine stimulants, cathinone causes dose-dependent reductions in eating and body weight (Islam et al. 1990 Zelger and Carlini 1980). Oral cathinone increases sexual arousal in rats, but does not affect erectile or ejaculatory responses (Taha et al. 1995). 

Figure 19.17 The biochemistiy and physiology responsible for penile erection. Sexual activity itself begins with a state of arousal that leads to erection. Arousal results in part from stimulation of the sense organs. The hypothalamus coordinates the sensations and activates the autonomic nervous system. Sensory nerves from the skin of the penis and other erogenous zones stimulate the parasympathetic system. This activates nitric oxide synthase and the resultant nitric oxide, via cyclic GMP, causes vasodilation of the arterioles. This increases blood flow through the corpora cavernosa which then expands producing an erection. Pheromones secreted by the female can stimulate the odour detecting system in the nasal cavity of the male (Chapter 12 and see above). Stress, however, activates the sympathetic system releases cyclic AMP which can result in vasoconstriction of the arterioles. Other factors that can interfere with an erection are physical fatigue and alcohol.

Even adults can still develop olfactory preferences that contravene those acquired before sexual maturity. Female laboratory mice imprinted by the odor of one mouse strain will prefer this odor even more if they are exposed to males of this strain as adults. However, if they are exposed to males of a different strain when sexually mature, their original odor preference will be reversed (Albonetti and D Udine, 1986). Naturally occurring sex or body odors may assume their sexual significance after association with sexual activity male mice were aroused by a perfume that they had experienced earlier on scented females they had interacted with (Nyby etal., 1978). Practitioners have known that adult mammals can acquire responses after exposure to certain animals. For instance, bulls of the Asian elephant that had been housed near African elephant bulls respond to temporal gland secretion and its three components phenol, 4-methylphenol, and (E)-farnesol from the latter species. Asian bulls thathad not been associated with African bulls did not respond (Rasmussen, 1988). 

BZs should be reserved for patients at low risk of substance abuse, those who require rapid relief, or those who have not responded to other therapies. Clonazepam is the most extensively studied BZ for treatment of generalized SAD. It improved fear and phobic avoidance, interpersonal sensitivity, fears of negative evaluation, and disability measures. Adverse effects include sexual dysfunction, unsteadiness, dizziness, and poor concentration. Clonazepam should be tapered at a rate not to exceed 0.25 mg every 2 weeks. Gabapentin was effective for SAD, and onset of effect was 2 to 4 weeks. j8-Blockers blunt the peripheral autonomic symptoms of arousal (e.g., rapid heart rate, sweating, blushing, and tremor) and are often used to decrease anxiety in performance-related situations. For specific SAD, 10 to 80 mg of propranolol or 25 to 100 mg of atenolol can be taken 1 hour before the performance. A test dose should be taken at home on a day before the performance to be sure adverse effects wUl not be problematic. Incomplete response to a first-line agent may benefit from augmentation with buspirone or clonazepam. 

Both acute and chronic alcohol use can lead to impotency in men. Increased blood alcohol concentrations lead to decreased sexual arousal, increased ejaculatory latency, and decreased orgasmic pleasure. Additionally, many chronic alcoholics develop testicular atrophy and decreased fertility the mechanisms are complex and likely involve altered hypothalamic function and a direct toxic effect of alcohol on Leydig cells. Testosterone levels may be depressed, but many men who are alcohol-dependent have normal testosterone and estrogen levels. Gynecomastia is associated with alcoholic liver disease and is related to increased cellular response to estrogen and to accelerated metabolism of testosterone. 

The present results are consistent with both animal and human research showing that female selection of male mates is influenced by body odor (Eklund et al., 1992 Wedekind et al., 1995). Phrased in the language of evolutionary mechanisms and parental investment theory, the Sensory Stimuli and Sexuality Survey suggests that sensory information about mates presumed to be indicative of offspring viability related to immune genetics (i.e., olfaction) is especially important for female heterosexual responses. For males information pertaining to female fecundity (as indicated by physical attractiveness attributes that can be seen) and offspring viability potential (olfaction) are most important in mate selection Olfaction, however, is less involved in sexual arousal for males than it is for females. 

As well as ensuring that the prospective mate is of the same species, the male s courtship performance allows females to choose between different males. The later stages of courtship may involve both partners in an alternating series of displays that inhibit aggression and fear responses and ensure synchrony of sexual arousaL... 

Bronson, F.H., and C. Desjardins Endocrine Responses to Sexual Arousal in Male Mice. Endocrinol. Ill, 1286-1291 (1982). 

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