Effects of p-chlorophenylalanine on reflexive and noncontact penile erections in male rats

To clarify the role of serotonin in penile erection, testosterone-primed castrated male rats were treated with the serotonin-synthesis inhibitor, p-chlorophenylalanine (pCPA), and reflexive erection (RE; male supine, penile sheath retracted) and noncontact erection (NCE; penile erection evoked by remote sexual stimuli) tests were performed. Half the males were injected with 100 mg/kg pCPA 4 times before each test; control males were treated with saline instead of pCPA. In the RE test, compared to the control group, pCPA-treated males had a shorter erection latency, but they also displayed fewer erections. NCE tests were conducted as a 2 x 2 factorial experiment: pCPA or saline, and estrous female present or absent. Only the pCPA-female Group had a high proportion of responders (68%), compared to 14-27% in the other Groups (p < 0.02). These results suggest that the serotonergic system exerts facilitative and inhibitory influences on different systems in regulating reflexive erection. On the other hand, serotonin appears to play an inhibitory role in the induction of noncontact erection, because pCPA did not directly induce erection, but rather facilitated the response to females.

Penile erection in response to remote cues from females: albino rats severely impaired relative to pigmented strains

Male rats have been observed to display erections when exposed to inaccessible estrous females, and it was suggested that these "noncontact erections" (NCEs) represent a species-typical response that may index sexual arousal. Initial efforts in other laboratories to repeat and extend this research were unsuccessful, and it appeared that differences in the rat strains being used might be responsible. To address this question NCE tests were given to rats of two albino strains, Wistar and Sprague-Dawley, and two pigmented strains, hooded Long-Evans and inbred Brown Norway. A high proportion of Long-Evans and Brown Norway rats displayed NCEs, whereas Wistar and Sprague-Dawley albino rats rarely did. Additional experiments did not reveal the reasons for the strain difference in NCE, but they provided evidence against hypotheses based on the relative erectogenic effect of albino and hooded estrous females, the attention paid to estrous females, the motor repertoire, or erectile function per se. Albinism-related neural pathology, possibly outside of the visual system, may contribute to the deficit in NCE in albino rats.

Placing erection in context: the reflexogenic-psychogenic dichotomy reconsidered

Penile erections are usually classified as arising from "reflexogenic" or "psychogenic" causes. In practice this dichotomy has translated, somewhat circularly, to a distinction between spinal vs. supraspinal mediation, pelvic vs. hypogastric neural mediation, and perineal somesthetic stimulation vs. stimulation of receptors innervated by the cranial nerves. Evidence for differential regulation of erection in different contexts is reviewed. Research ascribing a physiological role to the hypogastric nerves in psychogenic erection, exemplified by classic studies of cats and spinally injured men, is suggestive but not compelling. Somewhat stronger is evidence that erection in some contexts (e.g., nocturnal penile tumescence (NPT) in humans or touch-stimulated erection in rats) is more sensitive to androgen levels than in other contexts (e.g., visual erotic stimuli in men or copulation in rats). However, some of these differences may arise from the relative erectogenic strength of the stimuli, rather than from qualitative differences in androgen sensitivity of different contexts. More compelling is the possibility that conflicting interpretations of the role of dopamine in erection may stem in large part from differences among laboratories in the context in which erection is evoked. In light of the evidence reviewed, it seems unlikely that the conventional reflexogenic-psychogenic dichotomy should be retained, at least in its present form. As a first step, it may be worth considering that reflexive erections may not be limited to somesthetic perineal stimulation, but rather may also include stimuli received via the cranial nerves. Two alternatives to the standard reflexogenic-psychogenic dichotomy are proposed. The first is a minor revision in which two senses of psychogenic erection are distinguished: the weak, commonly used, sense would include erection resulting from any extrinsic nonsomesthetic stimulation, whether visual, auditory, or chemosensory. In this sense, reflexive erections and psychogenic erections may not be mutually exclusive. The strong sense of psychogenic erection would be limited to memory and fantasy. The origins of psychogenic erection in both senses need not be available to consciousness, which may account for apparently spontaneous erections. In the second alternative taxonomy, erectogenic stimuli are classified as contact (somesthetic) or noncontact, and their action in evoking erection is placed on a continuum of reflexivity. Erectile contexts could then be considered as orthogonal to the other two dimensions. Even without a change in taxonomy, the conduct and interpretation of research into erectile function may be expected to benefit from closer attention to differences and similarities between contexts and species, and to context-sensitive differences in the regulation of erection.

Noncontact stimulation from estrous females evokes penile erection in rats

Five experiments demonstrated that noncontact stimulation from estrous females evokes penile erection in a high proportion of sexually experienced male rats. In Experiment 1, 23 of 24 males (96%) displayed erections while separated from estrous females by a wire-mesh barrier, compared with 8% when no female was present. In Experiment 2, inaccessible estrous females stimulated erection in 100% of males, whereas only 38% responded to inaccessible unfamiliar males and 0% to inaccessible preferred food or an empty cage (n = 8/group). These data suggest that nonsexual arousing stimuli do not readily evoke erections. Experiments 3 and 4 demonstrated that bedding collected from estrous females is highly attractive to males, but is ineffective in promoting erections even when the males can burrow in the bedding. Therefore, estrous odors alone are apparently insufficient to stimulate erection. In Experiment 5, the percentage of males (n = 18) responding with erection did not vary significantly as a function of their exposure to ovariectomized females (67%), receptive but nonproceptive females (83%), or proceptive females (89%), but these stimuli were progressively more effective in reducing erection latency and increasing the number of erections displayed, suggesting that behavioral cues emitted by females promote erection. The display of erection by rats under the conditions used in these studies satisfies conventional criteria for recognition as psychogenic erections, which we have provisionally defined as erections that occur without concurrent somesthetic stimulation. The availability of a rodent model of psychogenic erection should foster analysis of its physiological mediation.

Effects of copulation on apomorphine-induced erection in rats

By testing the effects of antecedent copulation on subsequent apomorphine-induced penile erection we sought to test an implicit assumption in the research on drug-induced "spontaneous" erection--namely, that this research provides information relevant to the regulation of erection in copula. In experiment 1, male rats were observed after being injected SC with 0, 15, 30, 60, or 120 micrograms/kg apomorphine (APO); 60 micrograms/kg yielded the maximum probability of erection and yawning. In experiment 2, males were injected with 60 micrograms/kg APO after no exposure to females, after three intromissions, or after copulation to sexual satiety. There was no significant effect of three intromissions, but sexually sated males displayed no erections, the first evidence that copulation affects drug-induced erections. In experiment 3, males had one ejaculation, three intromissions, or no exposure to females immediately before injection with APO (60 micrograms/kg, SC) or ascorbic acid vehicle. APO induced both erection and yawning, but neither behavior was reliably affected by copulation in APO-treated males. Among vehicle-treated males, those having three intromissions or one ejaculation before the test had shorter erection latencies and more erections than males not exposed to females. Thus, a relatively small amount of copulation resulted in a level of erectile response similar to that of APO-treated males. Optimal doses of APO may be no more effective in promoting erection in male rats than are the natural neurochemical sequelae to copulation.

Physiology and mechanics of rat levator ani muscle: evidence for a sexual function

The levator ani (LA) of male rodents is a classic model tissue for the study of hormone-muscle interactions, although its functions remain unknown. Recordings during copulation from chronic electromyographic (EMG) electrodes in the LA and bulbospongiosus (BS) revealed that EMG activity in the LA and BS was tightly coordinated. The LA was not active during noncopulatory behaviors, including the 1-min interval surrounding defecation. Electrical stimulation of the LA motor nerves increased penile bulb pressure. Increases in penile bulb pressure following BS nerve stimulation were markedly attenuated after LA denervation and were reduced further by LA removal. Stimulation of the LA nerve yielded insignificant changes in rectal pressure. Perineal motion analysis demonstrated that the LA acts upon the penile bulb and the surrounding BS exclusively. Apparently the rodent LA muscle is an active component in a highly coordinated neuromuscular system augmenting penile erection and, contrary to its name, is most unlikely to participate in alimentary function.

Participation of pelvic nerve branches in male rat copulatory behavior

The role of the pelvic nerve branches in the mediation of copulatory behavior was investigated. The somatomotor or the viscerocutaneous branch of the pelvic nerve was bilaterally sectioned in sexually experienced male rats. Somatomotor branch surgery had no detectable effect. Viscerocutaneous branch transection altered copulatory parameters that reflect impairments in penile erection and seminal plug emission. The altered behavioral parameters approached or reached presurgical and sham values 21 days after transection, indicating that the damage to erectile and ejaculatory function was transient. It is suggested that animals with viscerocutaneous branch transection recover copulatory efficiency through a compensatory plastic mechanism, possibly involving the hypogastric nerve.

Relative androgen sensitivity of the vascular and striated-muscle systems regulating penile erection in rats

In this study we sought to compare the androgen sensitivity of the penile vascular erectile system with that of the striated muscles that augment the vascular effectors. All males were castrated 2 weeks before the experiments. At the time of castration, all males were implanted SC with a 45-mm testosterone (T)-filled Silastic capsule to maintain reflexive erections in ex copula tests. Experimental males had the bulbospongiosus (bulbocavernosus and levator ani) and ischiocavernosus muscles removed, while control animals underwent sham muscle excision surgery. After two baseline penile reflex tests, the T capsules were removed, and the groups were compared for the rate of loss of penile responses over 5 weeks. After these tests were completed, the T capsules were reimplanted and the two groups were compared for the rate of restoration of penile reflexes. These tests were conducted at 6, 12, 24, 36, 48, 72, and 96 h after reimplantation of the T capsules. Our results demonstrated that the vascular effector mechanisms responsible for initiating erections are androgen sensitive. The effects of T withdrawal and replacement on erection latency and low intensity erections (E1s) were manifested at about the same rate in the vascular and striated muscle effector systems. In contrast, the restoration of moderate intensity erections (E2s) by T occurred at a faster rate in rats with intact penile muscles. This result suggests that T was acting on the striated muscle effector systems to augment penile erection during this time, presumably due to the bulbospongiosus muscle exerting greater force on the penile bulb.

Electromyographic activity of rat ischiocavernosus muscles during copulation after treatment with a GABA-transaminase inhibitor

The administration of GABA-transaminase inhibitors (GABA-TIs) to male rats reduces the proportion of mounts that result in intromissions. Copulatory pelvic thrusting remains normal, despite the fact that animals treated with GABA-TIs show gross deficiencies in other motor acts. In order to determine whether altered sexual behavior produced by GABA-TI could be due to deficiencies in activity of striated penile muscles, we recorded the electromyographic (EMG) activity of the ischiocavernosus (IC) muscle during copulation in male rats treated with sodium valproate. The duration of IC EMG bursts was reduced by sodium valproate in separate tests that allowed or prevented intromission. There was no effect on EMG amplitude or frequency. It is suggested that insufficient activity of the IC muscles reduces the likelihood of vaginal penetration. The actions of GABA may be localized to hypothalamic or brain stem nuclei with GABAergic projections to the spinal motoneurons controlling the IC muscles, or GABA may act directly on these neurons.

Erectile mechanism in paraplegia

Erection is generally viewed as a reflex mechanism that can receive higher CNS influences. Paraplegic men who have lost reflex activity from the genital area are, therefore, treated as irreversibly impotent. However, the innervation of the male reproductive system suggests that two neural pathways innervate the genitals. In theory, the second (thoracic-lumbar) pathway should compensate for the loss of the first (sacral) pathway in cases of low spinal lesions. Clinical practice, however, ignores the TL pathway as a basis for treatment of spinal cord-injured men. This study used an animal model to demonstrate that the TL pathway could mediate penile responses in paraplegic rats. Eighty-five percent (85%) of spinal animals showed penile responses following hypothalamic (MPOA) stimulation despite a complete loss of peripheral erectile reflexes. These results not only have important implications from a clinical perspective, they further document the physiology of erection and support the view that erection is not a primary parasympathetic activity, but probably results from a sequence of sympathetic processes.

Erectile function and bulbospongiosus EMG activity in estrogen-maintained castrated rats vary with behavioral context

Electromyographic (EMG) activity in the bulbospongiosus muscles (BS) was recorded to monitor potential castration-induced alterations in muscle activity during copulation and reflexive erections. EMG recordings were made from intact male rats and from castrated rats maintained from 7 to 50 days on estradiol benzoate (300 micrograms/day) or testosterone (200 micrograms/day). Despite a 40-50% postcastration reduction in the weight of the BS and accessory sexual glands in estrogen-treated rats, the pattern of EMG activity during copulation was similar across groups. In estradiol-treated males, the EMG burst frequency during mounts and burst duration during intromissions exceeded the parameters of intact males and of castrated males maintained on testosterone. Between intromissions, and following ejaculatory patterns, estrogen-treated males displayed spontaneous muscle bursts accompanied by visually confirmed erection of the glans penis, but these males quickly lost the capacity for reflexive erections. These data demonstrate that despite castration-induced atrophy of the penile muscles and, presumably, their spinal motor nuclei, the motor output to these muscles is maintained following androgen removal. The capacity for substantial penile erection is retained during copulation long after reflexive erections have diminished.

Copulatory behavior and reflexive penile erection in rats after section of the pudendal and genitofemoral nerves

Two experiments probed the roles of the pudendal and genitofemoral nerves in sexual behavior. Male rats were tested for copulatory behavior and reflexive erections after transection of the sensory (SP) or motor (MP) branches of the pudendal nerves and, in Experiment 2, section of the genitofemoral (GF) nerve alone or in combination with the SP nerves. Damage to the GF nerve had no apparent effects. Division of the SP nerve severely impaired the ability of males to achieve intromission, and hence ejaculation, and reflexive erections were drastically reduced. However, this treatment caused impairments less complete than those previously described for more distal deafferentation by section of the dorsal penile nerves or by application of topical anesthetics to the glans penis. Penile autotomy following SP section was delayed but not avoided by daily treatment with amitriptyline. Transection of the MP nerves had the most drastic effects, preventing reflexive erections, although some intromissions (but no ejaculations) occurred during copulation. Although urinary function was also disrupted by MP transection, the impairment in sexual function is tentatively ascribed to chronic hyperinvolution of the penile corpora following loss of phasic vasoconstrictive stimulation normally supplied via the MP nerves. The pattern of results suggests that the pudendal nerves make different contributions to penile erection in different contexts.

Maintenance of erection of penile glans, but not penile body, after transection of rat cavernous nerves

Two experiments tested the widely held assumption that the cavernous nerves (CN) are essential not only to erection of the penile body, via the corpora cavernosa, but also to erection of the glans penis, via the corpus spongiosum. In Experiment 1, the copulatory behavior and reflexive erections of male rats were studied before and after the CN were transected bilaterally (n = 8), unilaterally (n = 6), or sham-operated (n = 6). In postoperative tests, bilaterally operated males were severely impaired in their attempts to effect intromission, and they had the expected deficits in reflexive erections of the penile body, but their capacity for erection of the glans penis was only minimally impaired. Sham-operated males were unaffected by surgery, and unilaterally transected males had intermediate values. Experiment 2 tested the hypothesis that activity of the bulbospongiosus muscles was responsible for the residual erectile capacity of the glans after CN transection in Experiment 1. Males had bilateral sections of the CN (n = 9), or of the nerves innervating the bulbospongiosus muscles (n = 10), or of both of these nerves (n = 8), or sham surgery (n = 10). Relative to CN transection alone, the combined denervation further reduced glans penis erections, but did not eliminate them. These results suggest that the cavernous nerves of the rat are not the only peripheral nerves facilitating vascular engorgement of the corpus spongiosum.

Electromyographic analysis of male rat perineal muscles during copulation and reflexive erections

Anatomical examination of the ventral bulbospongiosus (BS) muscle suggested that its proximal and distal portions may act during penile erection as a two-stage pump governing the intensity of glans erections. The coordination between these portions of the BS, and of the proximal BS with the ischiocavernosus (IC) muscle, was studied using electromyographic (EMG) recordings taken during copulation and reflexive erections. Mounts without intromission were accompanied by either strong IC activity with little or no proximal BS activity, or strong proximal BS activity preceding the onset of IC activity. Activity in the proximal BS during mounts was variable in both duration and amplitude but uniform in frequency. During mounts with intromission, EMG activity of the proximal BS consisted of two characteristic phases, an early phase of low-amplitude activity which was similar to proximal BS activity during nonintromissive mounts, followed by an intromissive phase of high-amplitude, high-frequency activity. During intromission patterns, IC activity reliably preceded proximal BS activity. Ejaculations were accompanied by stronger proximal BS activity than were other copulatory events and were followed by a series of proximal BS and IC bursts lasting for 10-20 seconds. During reflexive erections, EMG activity in the proximal BS was always fusiform and varied with the intensity of erection only in frequency. In contrast to the proximal BS, activity in the distal BS was similar in frequency and amplitude across copulatory and reflexive events. These findings suggest that: a) different motoneuron pools serve the different portions of the BS muscle; b) the distal BS does not differentially affect glans erection but may serve primarily to promote rigidity of the portion of the bulb that it surrounds, while the proximal BS acts as the variable aspect of a hypothetical two-stage pump, and c) activity in the IC must precede activity in the proximal BS to achieve intromission.

The ejaculatory reflex in copulating rats: normal bulbospongiosus activity without apparent urethral stimulation

Electromyographic activity was recorded from the bulbospongiosus muscles of intact, copulating male rats to test the hypothesis that urethral stimulation contributes to the ejaculatory reflex. Neither urethral anesthetization with lidocaine nor prevention of emission with guanethidine affected the rhythmic contraction of the bulbospongiosus muscle during the ejaculatory pattern. Urethral stimulation by the ejaculate apparently does not contribute to the regulation of the striated-muscle components of ejaculation-related reflexes in copulating male rats.

The ischiourethralis muscle of the rat: anatomy, innervation, and function

The ischiourethralis (IU), a striated perineal muscle presumed to be involved in sexual reflexes, was studied in the rat. The paired muscle arises from the penile crus and the penile bulb and unites in a raphe over the deep dorsal vein of the penis. Retrograde tracing studies show that the muscle is innervated by neurons in the dorsolateral nucleus of the lumbar spinal cord, a pudendal nerve motor nucleus which also innervates the ischiocavernosus muscle. Excision of the IU muscle did not interfere with the ability of males to display normal copulatory behavior, nor did it affect significantly the number and intensity of reflexive erections. It nevertheless remains possible that the IU may contribute to intense glans erection by compressing the deep dorsal vein.

Spinal block reveals roles for brain and spinal cord in the mediation of reflexive penile erections in rats

Five experiments were addressed at two questions: (1) is the influence of the brain on spinal control of reflexive erection exclusively inhibitory; and (2) are the effects of copulation on erectile potential mediated by the brain, the spinal cord, or both? After various amounts of antecedent copulation, spinal anesthesia was induced in male rats by tetracaine (TET) injected through chronically implanted cannulae into the thoracic or lumbar spinal subarachnoid space, and the animals were then tested for reflexive penile erections (supine position, penile sheath retracted, no phasic stimulation applied). In sexually rested rats, TET injected at either T4 or T10 reduced reflex latency but also reduced the number and intensity of responses. Penile erection was inhibited by TET injected at L5, the region of the cord receiving sensory and motor projections from the genitalia. In previous studies surgical transection of the thoracic cord facilitated erection latency and production. In the present experiments the divergent effects of intrathecal TET on these variables suggested that they are controlled by separate systems within the spinal cord and that in the sexually rested rat the net influence of the brain is to inhibit the latency system and excite the production system. After rats copulated to sexual satiety, thoracic spinal block did not reverse the complete abolition of reflexive erections, establishing for the first time that copulation has direct inhibitory effects on the spinal cord's intrinsic system. Fewer antecedent ejaculations had less inhibitory effects on reflexive erection, and TET then acted, as in rested males, to reduce the erection latency and the number of erections, indicating that copulation may act on the brain's descending influences on spinal systems. The overall pattern of results suggested that the brain exerts both excitatory and inhibitory influences on separate, interacting spinal mechanisms that regulate the latency to reflexive erection and the number and intensity of erections displayed.

Introduction--reproductive behavior: a symposium in honor of Frank A. Beach, 1911-1988

A symposium honoring the memory of Frank A. Beach (1911-1988) and celebrating his scientific contributions was held on June 12, 1989 during the 21st Conference on Reproductive Behavior (CRB). The papers arising from the symposium are introduced after a very brief history of the CRB and its origins in an annual meeting of West Coast American sex researchers that was organized by Frank Beach and his colleagues.

Quinelorane (LY163502), a D2 dopamine receptor agonist, facilitates seminal emission, but inhibits penile erection in the rat

Dopaminergic compounds have been shown to facilitate male sexual responses in various contexts. We investigated the effects of a specific D2 dopamine receptor agonist, quinelorane (LY163502), on sexual responses elicited in the restrained supine male rat (i.e., ex copula reflex tests). Penile erections, evoked by retraction of the penile sheath, were inhibited by systemic administration of 10 micrograms/kg quinelorane; however, the occurrence of seminal emission was dramatically increased. A smaller dose of 0.25 ng/kg was without effect. In a second experiment, intracranial microinjection of quinelorane was followed by ex copula reflex tests. The medial preoptic area (MPOA) has been previously implicated in the dopaminergic regulation of male copulatory behavior. The effects of an intra-MPOA injection of quinelorane on seminal emission and erectile responses were similar to those observed following systemic administration. These results are consistent with the hypothesis that DA receptors in the MPOA are important in the regulation of male sexual behavior and suggest that D2 receptors in the MPOA may decrease ejaculatory threshold while inhibiting erectile mechanisms.

Penile desensitization does not affect postcopulatory genital autogrooming in rats: evidence for central motor patterning

Postcopulatory genital autogrooming was studied in rats following desensitization of the glans penis due to topical application of an anesthetic ointment or to surgical transection of the dorsal penile nerve. These treatments sharply reduced the number of mounts resulting in intromission, but genital autogrooming was largely unaffected. The probability and duration of genital grooming were sensitive to the mount bout status of the copulatory event. The probability of autogrooming was higher, and the duration longer, after mounts that ended mount bouts and after intromissions, than after mounts that were incorporated within a mount bout. These findings suggest that the apparently compulsive genital autogrooming within a copulatory context is not regulated by afferent impulses from the penis, but may largely reflect central motor programing.

Inhibition of sexual reflexes by lumbosacral injection of a GABAB agonist in the male rat

The effects of gamma-aminobutyric acid (GABA) agonists on penile reflexes were investigated. An intrathecal injection of baclofen (0.2, 0.4, or 0.8 microgram), a GABAB receptor agonist, into the subarachnoid space of the lumbosacral spinal cord (L5-S1), resulted in a dose-related decrease in the number of animals responding in a penile reflex test. Doses of 0.2 and 0.4 microgram of baclofen decreased the number of erections; 0.4 microgram also increased the latency to the first glans erection. The highest dose of baclofen (0.8 microgram) completely inhibited penile responses in these tests. None of these doses, however, prevented rats from copulating to ejaculation. Antecedent ejaculation, which facilitated the onset of penile reflexes in saline controls, also blocked the inhibitory effects on penile responses by the lower doses (0.2 and 0.4 microgram) of baclofen, but was ineffective in animals treated with 0.8 microgram baclofen. In contrast to the inhibitory effects of baclofen in the lumbosacral cord, an intrathecal injection of baclofen (0.8 microgram) at thoracic segments (T8-T10) did not affect penile erections elicited following an ejaculation. The role of spinal GABAA receptors in sexual reflexes was assessed by intrathecal injection of a GABAA agonist. THIP (0.5.1. or 2 micrograms), onto the lumbosacral cord. Only at the largest dose of THIP were slight inhibitory effects on penile reflexes observed. Together, these data indicate that stimulation of GABAB receptors in the lumbosacral spinal cord inhibits erectile mechanisms ex copula.

Rapid effect of testosterone on striated muscle activity in rats

We addressed the question of how rapidly gonadal steroids might affect behavior by studying how fast testosterone (T) could augment the actions of the striated penile muscles and their associated penile reflexes. Eight male rats, functionally castrated 4 months before this study, bore chronically implanted electrodes in the bulbospongiosus (bulbocavernosus) muscle. The males were observed for the display of penile reflexes immediately after the injection of T (250 micrograms i.m.) and T propionate (250 micrograms s.c.), as well as after injections of only the oil vehicle. Overt penile responses were rare. However, in several tests subcutaneous twitching was observable near the midline posterior to the penis. These twitches were accompanied by electromyographic bursts and were attributed to contractions of the bulbospongiosus muscle. T reliably (p less than 0.025) accelerated the onset of electromyographic activity: 6 of the 8 males had electromyographic bursts before the 30-min limit, and 3 males responded within 6 min. This is the first demonstration of such a rapid action of androgens on behavior or its basis in striated muscle activity. The rapid muscular response to T was ascribed to steroid-sensitive neuronal membrane receptors. Such responsiveness could increase the intensity of penile reflexes within minutes after surges of luteinizing hormone and T have been induced by cues associated with estrous females and thereby could contribute to the fertility of mating.

The development of grooming and its expression in adult animals

We have seen that grooming is a class of heterogeneous activities, widely represented in animal taxa, yet sufficiently homogeneous within some phyletic groups to generate and test phylogenetic hypotheses. In the life of the grooming animal, the functions served by these activities are also diverse. Similar acts of grooming may serve different functions in different species or in different contexts. Sometimes these different functions can be discovered by careful attention to variations in the spatiotemporal patterning or sequencing of grooming elements. In several species a general cephalocaudal progression has been noted during both the ontogeny of grooming and during its expression in adults. During early development and in adulthood, the components or functional units of grooming appear to be hierarchically organized. Scratching with the hindpaw, for example, appears in rodents to be separate from the hierarchical branches in which one finds licking and face wiping. At least some transitions between functional units can be predicted from changes in the temporal patterning of one grooming unit (e.g., eye wipe) just prior to the onset of another unit (e.g., ear wipe). Analyses of genital and other types of grooming during two forms of sexual activity (copulation and the display of penile erections ex copula) were used to demonstrate once again that the stimulus regulation of grooming is context dependent. Among the implications of this review for the physiological study of grooming are the following: 1. Careful attention should be given to the spatiotemporal patterning of grooming, in order to reduce errors of "lumping" and "splitting" in classifying grooming acts, and also to detect alterations in the patterning when they occur. Such changes in patterning may be assumed to reflect changes in the physiological state of the animal. 2. Grooming acts that appear formally similar in different contexts may operate under rather different physiological systems. 3. Experimental manipulations may affect grooming directly, that is, by generating grooming efference without changing afference, or indirectly, by altering the "motivational state" or by creating stimulation that potentiates grooming, as from itching or from reafference due to provoking other behavior patterns.

Role of the bulbospongiosus muscles in sexual behavior and fertility in the house mouse

In two studies we investigated the role of the bulbospongiosus muscles (mBS) in the copulatory behavior, fertility, and ex copula reflexes of B6D2F1/J male mice. In Experiment 1, males had the mBS excised (BSx) or underwent a sham surgical procedure (SHx) and were tested for sexual behavior. BSx males had a significantly higher number of breaks (periods after intromission when the penis leaves the vagina and is reinserted without a dismount) per intromissive mount. On all other copulatory measures, BSx and SHx males were statistically indistinguishable. Vaginal smears taken daily from mated females revealed no effect of the male's condition on the rate of pseudopregnancy, but there was a higher rate of pregnancy in females mated to SHx males. In Experiment 2, males were tested for penile reflexes after midthoracic spinal transection. BSx males showed no intense erections, significantly fewer moderate erections, and significantly fewer clusters (series of reflexes separated by less than 15 sec). The results of the two experiments suggest that in mice the mBS contributes to the penile erection necessary to maintain intromission during thrusting. It also appears that in mice, as in rats, the actions of the mBS in promoting the formation of penile cups contribute substantially to fertilization.

An IBM-PC based data collection system for recording rodent sexual behavior and for general event recording

A microcomputer (IBM-PC) based data collection system for the acquisition and analysis of male rodent copulatory behavior and its reflexive components has been developed. This software features ease of data entry, flexibility across experimental protocols, and built-in tutorials. The program for the recording and analysis of sexual reflexes of the male is readily adapted for recording other behavior patterns.