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At least 235 records · Page 13Linked to original sources
PubMed1988

Ultrasonic vocalizations in male rats following acquisition of copulation-illness associations.

Brief 50-kHz ultrasonic vocalizations are emitted by male rats during copulatory encounters with sexually receptive females. These vocalizations also occurred during pairings with estrous females in male rats whose copulatory behaviors had been associatively inhibited by LiCl-induced aversive contingencies. Longer 22-kHz calls, typically emitted during the postejaculatory refractory period, were not observed in these males. These results demonstrate a dissociation of behaviors that were (mounts, intromissions, and ejaculations) and were not (50-kHz vocalizations) associatively inhibited by LiCl.

Animals↗
PubMed1989

Paced copulation in rats: effects of intromission frequency and duration on luteal activation and estrus length.

When estrous female rats regulate or pace (P) the timing of vaginal intromissions received from males during mating, the stimulation is more effective in inducing luteal function and abbreviating the period of receptivity than is nonpaced (NP) stimulation. The present studies examined whether the coital stimuli necessary for each of these functional consequences are similar. In Experiment 1, estrous females received either 5 or 10 intromissions from males in P or NP tests; control animals received mounts-without-intromission (MO). The duration of estrus was not affected by 5P, 5NP, or 10NP stimulation, but was significantly abbreviated in 10P animals. In contrast, activation of prolonged luteal function occurred in 70% of 5P females compared to only 10% of 5NP females; luteal activation was similar in 10P and 10NP females (74% for both groups combined). In Experiment 2, male copulatory behaviors were compared in tests with P and NP females. Males tested with P females exhibited significantly longer intromission durations (616 +/- 21 msec) than did males tested with NP females (527 +/- 30 msec). Other measures of male copulatory performance such as the number of intromissions to ejaculation and the ejaculation latency did not differ between groups. These studies demonstrate that luteal activation is more readily induced by paced coital stimulation than is abbreviation of estrus. In addition, they suggest that differences between P and NP females in the behavioral and neuroendocrine responses to coital stimulation may result from differences in intromission duration displayed by males under these test conditions.

Animals↗
PubMed1985

Fluprazine hydrochloride decreases copulation in male rats.

The copulatory performance of 18 sexually experienced male rats was tested 30 min after IP injection of the phenylpiperazine, Fluprazine Hydrochloride (4 and 8 mg/kg), or saline solution. Three 20-min tests with an estrous female were conducted at weekly intervals. Each drug dose produced a significant depressive effect on copulatory behavior (latency to and frequency of intromissions and ejaculations) without affecting social investigation. The increased latencies to mounting and intromission observed at both doses suggest that the primary action of the Fluprazine Hydrochloride is to interfere with the transition from social to copulatory patterns. Although the drug's mode of action is currently unknown, the present findings suggest that it operates on some common mediator of sexual and aggressive behavior.

Animals↗
PubMed1994

A D1 agonist in the MPOA facilitates copulation in male rats.

The classic dopamine agonist apomorphine, microinjected into the medial preoptic area (MPOA), enhances the copulatory behavior of male rats, while pharmacological blockade of endogenous dopamine inhibits sexual behavior. We now report that MPOA injections of 10 micrograms of the selective D1 agonist dihydroxyphenyl-tetrahydrothienopyridine (THP) significantly increased the number of ejaculations, while decreasing the latency to ejaculate in a 30-min test. These effects were not observed following coadministration of the selective D1 antagonist SCH-23390 with 10 micrograms THP. This enhancement may be related to a D1-stimulated facilitation of penile erections.

Animals↗
PubMed1994

Structural identification, neuronal synthesis, and role in male copulation of myomodulin-A of Lymnaea: a study involving direct peptide profiling of nervous tissue by mass spectrometry.

We used a strategy combining immunodetection, peptide chemistry, and a novel method, direct peptide fingerprinting of neurons and small pieces of nerve by using matrix-assisted laser desorption ionization mass spectrometry, to structurally identify and localize the neuropeptide myomodulin-A in the mollusc, Lymnaea stagnalis. Lymnaea myomodulin appeared to be identical to Aplysia myomodulin-A and is produced by many central neurons, including neurons located in the ventral lobe of the right cerebral ganglion that innervate the penis complex via the penis nerve. Myomodulin-A could also be characterized from the penis complex, and physiological concentrations of the peptide enhanced the relaxation rate of electrically induced contractions of the penis retractor muscle in vitro in a dose-dependent fashion.

Animals↗
PubMed1992

Concurrent wet dog shaking and inhibition of male rat copulation after ventromedial brainstem injection of the 5-HT2 agonist DOI.

Systemic administration of drugs that augment 5-HT2 activity generally induces 'wet dog' shaking (WDS) in rats. This suggests that the naturally occurring form of WDS seen in untreated rats may also serve as a behavioral index of 5-HT2 receptor activation, during the performance of other behaviors. Indeed, spontaneously occurring WDS has previously been reported to be inversely related to male rat copulatory proficiency. In order to examine a potential central nervous system mechanism subsuming these behaviors, male rats were tested for WDS and sexual behavior after brainstem administration of the 5-HT2 agonist DOI. Male Long-Evans rats were implanted with cannulae terminating in the region of the nucleus raphe obscurus/inferior olive, through which they received injections of DOI (0.1-10 micrograms). DOI produced a dose-dependent decrease in sexual behavior and concurrent increase in WDS. Pretreatment with the 5-HT2 antagonist ritanserin effectively blocked the effects of DOI. The results suggest that WDS and copulatory behaviors are modulated by a shared brainstem substrate. It is possible that the results may be the behavioral concomitant of recently described brainstem cells, with bifurcating axons, that project to both the medial preoptic area and the cervical spinal cord.

Amphetamines↗
PubMed2004

Activation of mu opioid receptors in the medial preoptic area following copulation in male rats.

The current study tested the hypothesis that sexual behavior is a biological stimulus for release of endogenous opioid peptides. In particular, activation of mu opioid receptors (MOR) in the medial preoptic area (MPOA), a key area for regulation of male sexual behavior, was studied in male rats. MOR endocytosis or internalization was used as a marker for ligand-induced receptor activation, utilizing confocal, electron, and bright microscopic analysis. Indeed, mating including one ejaculation induced receptor activation in the MPOA, demonstrated by increased immunoreactivity for MOR, increased numbers of endosome-like particles immunoreactive for MOR inside the cytoplasm of neurons, and increased percentage of neurons with three or more endosome-like particles inside the cytosol. Moreover, it was demonstrated that MOR activation occurred within 30 min following mating and was still evident after 6 h. Mating-induced internalization was prevented by treatment with the opioid receptor antagonist naloxone before mating, suggesting that mating-induced receptor activation is a result of action of endogenous MOR ligands. i.c.v. injections of MOR ligand [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin resulted in internalization of the MOR in a similar manner observed following mating. Finally, mating induced Fos expression in MOR containing neurons in the MPOA. However, naloxone pretreatment did not prevent Fos activation of MOR neurons, suggesting that Fos induction was not the result of MOR activation. In summary, these results provide further evidence that endogenous opioid peptides are released in the MPOA during male sexual behavior.

Analgesics, Opioid↗
PubMed1994

Telemetric monitoring of intracavernous pressure in freely moving rats during copulation.

Changes in intracavernous pressure (ICP) were recorded in freely moving rats by means of a catheter implanted in the corpus cavernosum and connected to a pressure transducer located subcutaneously. Intracavernous pressure changes and copulatory events (mounts, intromissions and ejaculations) were recorded during several overnight testing sessions with 12 rats in the presence of receptive females. Video recordings of sexual behavior in the implanted and nonimplanted rats revealed that the ICP device did not impair copulatory behavior. Comparison between copulatory behavior and ICP changes revealed that ICP profiles could identify the number of intromissions and ejaculations as well as the timing of these events. The results showed that during mounts, intromissions and ejaculations, ICP increases were 36.9 mm. Hg, 62 mm. Hg and 106.3 mm. Hg in 4 rats. The increases in ICP during mounts and intromissions appeared higher in sexually experienced as compared with sexually naive rats. These results demonstrate the reliability of the telemetric measurement of ICP in freely moving rats under natural physiological conditions. The model provides quantitative data for research on the neurophysiology of penile erection and evaluation of oral treatments for impotence.

Animals↗
PubMed2003

Play, copulation, anatomy, and testosterone in gonadally intact male rats prenatally exposed to flutamide.

The role of prenatal androgen on the differentiation of sexually dimorphic juvenile play and adult copulatory patterns was evaluated in male offspring of rats injected with 5 mg of the androgen receptor blocker flutamide (4'-nitro-3'-trifluoromethylisobutyranilide) from Days 11-21 of pregnancy. Rough-and-tumble play was incompletely masculinized in flutamide-exposed males at 31 days of age. The copulatory potential tested at 70 days of age was severely attenuated by prenatal flutamide. There was no ejaculatory behavior, low levels of intromissions, and depressed levels of nonintromittive mounting when the animals were tested while gonadally intact. Adult plasma levels of testosterone (T) were not different in flutamide-exposed males and controls, but testicular and epididymal weight, anogenital (AG) distance, and penile length were reduced. While reductions in intromittive mounting and ejaculatory behavior may be due to the abnormalities in the external genitalia, the incomplete masculinization of play and the reduction in nonintromittive mounting probably resulted from effects the androgen antagonist exerted on sexual differentiation of the central nervous system. These data suggest that androgen released prior to birth is needed for the full masculinization of juvenile play behaviors in the rat, just as it is for the adult copulatory pattern.

Androgen Antagonists↗
PubMed2000

Haloperidol challenge during copulation prevents subsequent increase in male sexual motivation.

Male rats manifest an increase in sexual motivation following sexual experience. The current experiment was devised to investigate the role of dopamine in this process by assessing whether sexual behavior occurring in the presence of the dopamine receptor antagonist, haloperidol, would continue to alter the subjects' subsequent sexual motivation. Four groups of male Long-Evans rats (total N=34) traversed an operant runway once per day for one of two goalbox targets: a nonestrous or estrous female. Following establishment of baseline run times (10 trials), all males received one ejaculation with a receptive female in a separate testing environment. Subjects were pretreated with vehicle or one of three doses of haloperidol (0.05, 0.075, 0.10 mg/kg) 45 min prior to being paired with the receptive female. All subjects successfully achieved ejaculation under these conditions. Subjects were then re-tested within the runway for their motivation to approach the two types of female targets (10 trials). Vehicle-treated subjects expressed the expected increase in sexual motivation following sexual experience, while haloperidol treatment dose-dependently attenuated this effect. Subjects that received the highest haloperidol dose subsequently manifested increased run times and intra-runway "retreat" behaviors, suggesting that female cues may have become associated with an aversive sexual experience. These results are consistent with the view that dopamine systems play a role in the rewarding or reinforcing consequences of male sexual behavior.

Animals↗