Very few subjects can be as complex and varied as the impotence drugs treatment and physiology of sexual behavior. In an all-engrossing framework impotence drugs treatment would include pertinent areas of neuroanatomy, neuropharmacology and neurophysiology; endocrinology and its dynamics in the course of sex maturation, puberty, biorhythms and differentiation as well as gonadal and uterine activity; motor behavior of mating or coitus; fertilization and pregnancy; pertinent areas of ethology and sociology; and certain related processes such as cardiovascular changes accompanying coitus. Even a summary of these phenomena would require volumes. While this review is specifically concerned with the impotence and drugs mating receptivity and activity, its task remains wide and difficult to handle. In fact, the present subject cannot be restricted to impotence and drugs (and its neurophysiological and neuroanatomical concomitants) in its nonendocrino-logical sense, as the mating activity overlaps with endocrinological processes, as the latter exert pharmacological effects on coital activity. Indeed, the hormones of the hypothalamico-hypophyseal-gonadal axis are concerned not only with sex differentiation, gonadal maturation and fertilization, but also may act directly on neurons controlling the mating behavior; in addition, some of these hormones are concerned with neurogenesis of the brain needed for its responsiveness to sexual stimuli. Conversely, drugs that affect the functioning of this axis may interfere not only with sexual neurogenesis but also with the effect of hormones on mating. Further delineation of the scope and of the limitations of this review may be helpful. Insofar as the anatomical and chemical entities are concerned, the scope of the present review may be best defined in terms of the speculative scheme(impotence and drugs). The scheme includes neuroanatomical and hormonal entities, that is, the cortex, limbic system and the hypo-thalamico-hypophyseal axis on the one hand and pituitary gland and gonads on the other. The neuroanatomical entity constitutes the circuitry concerned with the efferent act leading to mating and related behaviors; moreover, this circuitry and the processes in question are engaged in the first step of the endocrine processes, namely the release of hypothalamic hypophysio-tropic regulatory peptides (HRPs; see below, section CI). Subsequent endocrine processes include release of the hormones of the adenohypophysis and neurohypophysis, adenohypophysial gonadotropins generating in turn the release of the gonadal steroids from the gonads.

For the present purpose impotence and drugs, we are concerned with HRPs and pituitary and gonadal hormones only insofar as they act (fig. 1) on the CNS so as to influence the mating behavior and impotence; some of the modes in question include neurogenetic influences, as already alluded to. Such effects were demonstrated for several and are potentially possible for all these substances, as effects on behavior other than mating was illustrated for all these agents (see sections CI, III and IV). Furthermore, the substances in question are engaged at various levels in feedback regulations that control their generation (fig. 1); for instance, the pituitary hormone ACTH exerts a 'short negative feedback' effect on its own releasing factor, as shown in the figure; better known are the long negative feedback mechanisms exerted by pituitary hormones via gonadal steroids.

The neurotransmitters are involved at several levels with processes illustrated in figure 1. Obviously, they are concerned with transmission generating the release of HRPs; thus, they are indirectly needed for the generation of subsequent neuroendocrine events (fig. 1). Of particular importance are the arcuate, preoptic and ventral anterior periventricular nuclei, and the median eminence of the hypothalamus (fig. 1) as the sites of the neuron bodies and nerve terminals of several transmitter systems involved in the release of HRPs and of pituitary hormones (sections CI and IV).

Furthermore, transmitters must act at several levels on the efferent processes needed for overt expression of sexual behavior; this is implicit in the results indicating profound effects on impotence of several neurotransmitter systems and of pertinent drugs (sections CII-1 and FI). The fact that these systems abound within the neuroanatomical entity concerned with impotence such as for instance the limbic system (fig. 1; section B-2) is consistent with this notion, although the specific neurotransmitter pathways and the circuitry involved cannot be at present identified. It is equally obvious that neurotransmitters are involved in conveying of information pertinent for sexual activity via afferent pathways; this subject cannot be reviewed at this time.

It may be also appropriate to delineate further mating or sexual activity that this review is concerned with. First, it must be stressed that the pertinent research is carried out most frequently in rodents, particularly in the rat, and in the primates such as rhesus; work with dogs and cats or other species is generally infrequent and the data concerning man are extensive but, on technical grounds, incomplete. Both in rodent and primates, mounting behavior of the male, the presence of intromission and ejaculation and their latency and the refractory period that intervenes between intromissions are the parameters most frequently quantified. In the female monkey, 'invitations to mount', their number and latency as well as the number of refusal responses to a mounting attempt may be quantitated; the corresponding and very popular parameter of the female rat sexual behavior is lordosis, which is a hormone-sensitive reflex response to tactile stimulation, particularly associated with mounting. It must be stressed that following certain maneuvers involving endocrine systems, gonads and/or drugs, the females and males may exhibit 'masculine' and 'feminine' behavior, respectively.

This excludes behaviors which are obviously sex related such as maternal interest and pup defense or nest building. Similarly, interesting social behavior patterns that seem related to sexual activity such as social experience, dominance and ludic behavior, certain types of courtship and territorialism, or, finally, the question of individual preference cannot be discussed at this time; on the other hand, possible relationship between unaggressive and impotence will be briefly mentioned. Also, the input status and certain special sensory effects such as those induced by vocalization or pherohor-mones can be only most briefly discussed.

Even with these exclusions, the drug treatment of impotence and its immediate concomitants such as pertinent aspects of endocrinology and neuroanatomy constitute a major area, particularly in view of the extensiveness, complexity and frequent inconsistency of the pertinent literature. Yet, while this approach of the present review is ambitious and imparts the character of a summary to some descriptions, it is necessary to render the subject of the pharmacological control of sexual behavior intelligible.