Isolation-induced facilitation of male sexual behavior in mice.

Compared sexual performance of 288 CD-1 male mice housed individually or in groups of 3 or 12. Exp I examined males presented at weekly intervals with ovariectomized, estrogen-primed, progesterone-treated females. Performance in isolates was consistently superior and reached an asymptote that was twice that of grouped Ss. Reversal of housing conditions reversed performance. Exp II varied intervals of isolation among Ss finding facilitation at several intervals. Exp III compared Ss under different population densities. Density did not alter the effects of isolation and grouping. In all experiments, additional tests with target males indicated that aggressive and sexual performances were moderately correlated and responded similarly to parametric manipulations. These results parallel and extend studies of isolation-induced aggression. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen facilitation of progesterone-induced incubation behavior in castrated male ring doves.

Previous studies have shown that incubation is shared by both male and female ring doves and is induced, without prior participation in courtship and nest building, by progesterone (100 mg/day) treatment. In the present experiment with 52 mature male ring doves, it was shown that the effectiveness of progesterone is markedly reduced by castration and restored after estradiol benzoate (200 mg/day * 14) pretreatment, thus simulating the endocrine events which precede incubation in the female. Estrogen also stimulated the appearance of nest cooing (another isomorphic behavior) but not bow cooing (a male-specific display). Results are discussed in terms of hormonal specificity underlying reproductive behavior and the possible physiological roles of estrogen and progesterone in the ring dove. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decline of sexual behavior in castrated male rats: effects of female precopulatory behavior

Ventricle cells from neonatal rats were cultured in a medium preventing cell proliferation on a modified Roller apparatus with a defined pericellular oxygen partial pressure (pO2) of 38 or 0.6 mm Hg for about one week. The cells were harvested after the second and eighth day of culture (corresponding to one or seven days of culture under a defined pO2) and prepared for electron microscopy. Electron micrographs of this material were examined by stereologic techniques. The obtained results showed some deviations of mitochondrial fine structure of heart muscle cells depending on oxygen supply. During cultivation with a pO2 of 0.6 mm Hg (hypoxic conditions) we observed a proportional increase in mitochondria without cristae and an increase in size accompanied by a more irregular shape. On the contrary, the mitochondria of cells cultured with a pericellular pO2 of 28 mm Hg, which we consider to be a normoxic condition, did not show any deviation of inner membrane arrangement, but an increase in number and a decrease of size during cultivation was apparent. The mitochondria-myofibrils ratio decreased during cultivation in both conditions of oxygen supply. The ratio between sarcoplasmatic reticulum and myofibrils decreased markedly at a pO2 of 0.6 mm Hg.     

Comparison of the effects of stanozolol, oxymetholone, and testosterone cypionate on the sexual behavior of castrated male rats.

In 3 experiments, adult male Long-Evans rats were castrated and treated daily with an anabolic-androgenic steroid (AAS) compound (either stanozolol, oxymetholone, or testosterone cypionate) for 6 weeks. Subjects were assigned to 5 groups that received injections of a high, medium, or low dose of the AAS, testosterone propionate, or the oil vehicle. Stanozolol failed to maintain ejaculation at any dose tested. Although some subjects receiving the low dose of oxymetholone ejaculated, oxymetholone generally failed to stimulate ejaculation above the levels of the oil group. Testosterone cypionate sustained ejaculation at all doses tested. The relative potency of the medium dose of each AAS in the sex accessory tissues was (from most potent to least potent): testosterone cypionate?>?stanozolol?=?oxymetholone?=?oil. Thus, these 3 AAS compounds produced a range of behavioral and endocrine responses in castrated male rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the effects of 17 α–methyltestosterone, methandrostenolone, and nandrolone decanoate on the sexual behavior of castrated male rats.

In a series of 3 experiments, adult male Long-Evans rats were castrated and treated with 1 of 3 different anabolic-androgenic steroid (AAS) compounds ( 17 α-methyltestosterone, methandrostenolone, or nandrolone decanoate) for 6 weeks. In each experiment, subjects received daily injections of a high, medium, or low dose of AAS or the oil vehicle. The AAS effects on body weight in gonadectomized male rats were modest, and no effects on locomotor activity were observed. The AAS compounds administered at doses comparable with human abuse levels were not equipotent in maintaining male sexual behavior patterns (nandrolone decanoate > methandrostenolone > 17 α-methyltestosterone). In addition, the behavioral actions of AAS compounds did not parallel stimulation of sexual accessory glands. The authors reported that this study is the first to quantify the dose–response characteristics of individual AAS compounds with regard to these behavioral and endocrine measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emergence of displacement activities in the male rat following thwarting of sexual behavior.

Conducted 7 experiments with Wistar rats, who were observed in a mating area equipped with a water spout, that revealed the emergence of displacement drinking and hindlimb scratching in noncopulating castrated males and in males with medial preoptic (MPO) lesions exposed to sexually attractive stimulus females. By contrast, sexually quiescent males in the postejaculatory refractory period showed no evidence of displacement activity, and anestrous females displayed only moderate increments in drinking and scratching, compared with copulating estrous females. In both castrated and MPO-lesioned males, the amount of displacement activity was inversely related to strength of masculine sexual behavior, and in castrated Ss, displacement behavior was suppressed by the subcutaneous implantation of a testosterone-filled capsule. When no stimulus females were present, no difference in drinking and scratching by control, castrated, and MPO-lesioned Ss was discerned. Sexually inactive females elicited less displacement activity in castrated Ss than did females in estrus. However, unreceptive stimulus females frequently elicited displacement behaviors in normal sexually active males. Findings are discussed in relation to current concepts of psychological organization of masculine sexual behavior. It is suggested that the emergence of displacement behavior in castrated, MPO-lesioned, and normal males paired with anestrous females may be due to the thwarting of sexual motivation. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysiological correlates of copulatory behavior in the male rat: Evidence for a sexual inhibitory process.

Investigated the dynamics of hippocampal and cortical activity during copulation in 8 male Sprague-Dawley rats. Hippocampal theta rhythm accompanied appetitive behaviors, e.g., watching, sniffing, approaching, and mounting the female. Theta continued after most mounts without intromission, whereas intromission or ejaculation was followed by slowing and desynchronization of hippocampal activity. During rest, high-amplitude irregular slow waves and spindling appeared in the hippocampus and eventually in the cortex. Rest occurred primarily as S approached ejaculation and in the initial part of the postejaculation interval. Rest and its accompanying EEG spindling are interpreted as a developing sexual inhibitory process. A model involving interaction between a postulated arousal process and opponent sexual inhibitory process is presented. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pharmacokinetic and pharmacodynamic studies of L-dopa in rats. II. Effect of L-dopa on dopamine and dopamine metabolite concentration in rat striatum

The purpose of this investigation was to quantitatively describe the time courses of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) concentrations in the striatum after L-dopa injection using a constructed dopamine metabolism model. The time courses of dopamine, DOPAC and HVA concentration in the striatum of rats was determined before and after the rapid i.v. injection of 10, 50 and 100 mg/kg using the same animals as in the previous report. The endogenous dopamine, DOPAC and HVA concentrations in the striatum before L-dopa administration were 5.9 +/- 0.7 micrograms, 3.6 +/- 0.4 micrograms and 1.0 +/- 0.2 micrograms/g, respectively. The dopamine concentration in the striatum increased immediately after L-dopa injection, with the peak concentration (15.9 +/- 0.5 micrograms/g) occurring at 3 min; then it returned to the pre-medication level until 2 h at 100 mg/kg dosing. The time course of dopamine concentration in the striatum was analyzed on a constructed dopamine metabolism model which has a zero-order production rate for the production of dopamine (i.e. release from the dopamine neuronal terminals) and two apparent first-order clearance terms, one from L-dopa to dopamine, which was estimated in the previous report, and the other from dopamine to dopamine metabolites (DOPAC and HVA). However, the time course of dopamine concentration in the striatum could not be described by this model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Olfactory conditioning of sexual behavior in the male rat (Rattus norvegicus).

The role of classical conditioning in the copulatory preferences of male Long-Evans rats (Rattus norvegicus) was examined by pairing a neutral olfactory stimulus (almond odor) with female reproductive status. During training trials, the males were given access to scented or unscented females that were either sexually receptive or unreceptive. Subsequently, copulatory preferences were tested in males given simultaneous access to 2 receptive females, 1 scented and 1 not. Males trained with scented-receptive females displayed an ejaculatory preference for the scented female. Males trained with scented-unreceptive females or with unscented-receptive females displayed an ejaculatory preference for the unscented female. Males displayed no preference when scent and reproductive status were paired randomly. These results demonstrate that classical conditioning produces an ejaculatory preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of sequential preoptic and mammillary lesions on male rat sexual behavior.

Observed the sexual behavior of 52 male Sprague-Dawley rats prior to and following bilateral medial preoptic, unilateral medial preoptic, bilateral posterior preoptic, bilateral mammillary, and sham lesions. Bilateral medial preoptic lesions and mammillary lesions were made either simultaneously or sequentially within the same Ss in separate groups. Mammillary lesions had no effect on sexual behavior. Complete destruction of the medial preoptic area made prior to, simultaneous with, and following mammillary lesions completely abolished mating behavior. Partial destruction of the medial preoptic area increased mount and intromission latencies and slightly increased ejaculation latency. Results suggest that since there was no change in the postejaculatory-refractory interval, the medial preoptic area mediates sexual arousal but apparently is not involved in a copulatory-ejaculatory mechanism. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An NMDA antagonist impairs copulation and the experience-induced enhancement of male sexual behavior in the rat.

Sexual experience facilitates subsequent male sexual behavior; activation of the N-methyl-D-aspartate (NMDA) glutamate receptor may play a role in this experience-induced enhancement. In this article, the authors report that systemic injections of MK-801, an NMDA receptor antagonist, impaired male sexual behavior in sexually naive and sexually experienced male rats. Furthermore, saline-treated rats that received 7 daily exposures to an inaccessible estrous female instead of sexual experience displayed enhancement of copulation on the following day. Injections of MK-801 before each of these exposures inhibited the experience-induced enhancement on the drug-free test on Day 8. These data suggest that stimulation of NMDA receptors enhances sexual performance immediately and mediates the experience-induced enhancement of subsequent copulatory behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Progesterone has rapid and membrane effects in the facilitation of female mouse sexual behavior

Ovariectomized (ovx) mice require both estradiol (E2) and progesterone (P) administration to reinstate feminine sexual behavior (lordosis). The importance of P's actions at E2-induced intracellular progestin receptors (PRs) to facilitate lordosis was investigated in PR knockout (PRKO) mice, PRKO's wild type littermates (C57X129), and wild type C57BL/6J (C57) mice. Subjects were ovx, E2-primed (0.5 microg) and tested following intravenous (i. v.) and intercereberal P. Intravenous P (200 microg) significantly increased lordosis of all mice within 10 min of P, but vehicle infusion did not (Experiment 1). Intravenous P significantly increased the amount and duration and reduced the latency of lordosis, over that seen with vehicle infusion, in PRKO and wild type mice. Whole brain concentrations of P and its 5alpha-reduced metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), which has low affinity for intracellular PRs, were also increased following P compared to vehicle infusion. Progesterone, but not vehicle infusions, significantly increased the number of PR-immunoreactive (PR-IR) cells in the ventromedial hypothalamus (VMH) of C57 and C57X129 mice and increased number of 3alpha, 5alpha-THP-immunoreactive (3alpha,5alpha-THP-IR) cells in the ventral tegmental area (VTA) of all mice. In Experiment 2, P conjugated to bovine serum albumin (P:BSA) increased lordosis when applied bilaterally to both the VMH and VTA of E2-primed mice more than BSA implants. Progesterone implants increased the number of PR-IR cells in the VMH of C57 and C57X129 mice and the number of 3alpha,5alpha-THP-IR cells in the VTA of all mice. The rapid facilitation of lordosis with i.v. P infusion and increases in lordosis when P's effects are relegated to the membrane in the VMH and VTA of PRKO and wild type mice suggest that P may facilitate lordosis through actions at substrates other than intracellular PRs. The present findings suggest a role of 3alpha,5alpha-THP.     

Effects of losartan on the sexual behavior of male rats

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.     

Neuromuscular facilitation induced by muscarinic antagonists in the rat isolated diaphragm

1. Atropine (EC50 = 87 microM), pirenzepine (447 microM), and AF-DX 116 (95.5 microM), but not 4-DAMP (at concentrations of up to 110 microM), produced neuromuscular facilitation and antagonized the oxotremorine-induced neuromuscular blockade in the rat isolated diaphragm. 2. Atropine, pirenzepine, and AF-DX 116 did not change the responses of curarized diaphragms to direct stimulation, or the twitch tension produced by retrograde injection of acetylcholine. 3. These results indicate that neuromuscular facilitation induced by muscarinic antagonists may depend on drug interaction with the M2 subtype of muscarinic autoreceptors to increase acetylcholine output in the neuromuscular junction.     

Differential rates of exhaustion and recovery of several parameters of male rat sexual behavior.

Studied sexual exhaustion of 12 sexually experienced Long-Evans male rats with respect to several copulatory measures. The ejaculatory latency, intercouplatory interval, and intromission frequency demonstrated a U-shaped curve, exhibiting high values for the initial ejaculatory series, falling to a minimum at an intermediate ejaculatory series, and again increasing at exhaustion. The absolute refractory period of the postejaculatory interval (measured at vocalization termination) increased linearly, whereas the relative refractory period (the remaining portion of the postejaculatory interval) was a positively accelerating function. Partial recovery tests demonstrate that the preejaculatory measures and absolute refractory period substantially returned to baseline values by Day 6, while the relative refractory period was still extended. The significance of these data to the theoretical modeling of sexual behavior is discussed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of aggression, sexual behavior and fertility in adult male rat following long-term ingestion of four industrial metals salts

1. The effect of long-term ingestion of the industrial metals salts, manganese sulfate, aluminum chloride, lead acetate and copper chloride was investigated on aggression, sexual behavior and fertility in male rat. Adult male rats ingested solutions of these salts along with drinking water at a concentration of 1000 p.p.m. for 12 weeks. 2. Male rat sexual behavior was suppressed after the ingestion of manganese sulfate, aluminum chloride, lead acetate and copper chloride. The ingestion of solutions of these salts markedly prolonged the intromission and ejaculation latencies. Aluminum chloride and copper chloride reduced the copulatory efficiency. 3. Male rat aggression was also abolished after the ingestion of manganese sulfate, aluminum chloride, lead acetate and copper chloride. The ingestion of solutions of these salts markedly suppressed lateralizations, boxing bouts, fight with stud male and ventral presenting postures. 4. Fertility was reduced in male rats ingested with lead acetate. The total number of resorptions was increased in female rats impregnated by males ingested with manganese sulfate and lead acetate. 5. Body, absolute or relative testes, seminal vesicles weights were dropped in adult male rats ingested with manganese sulfate, aluminum chloride, lead acetate and copper chloride. However, the absolute or relative preputial gland weights were not affected. Collectively, these results suggest that the long-term ingestion of manganese sulfate, aluminum chloride, lead acetate and copper chloride would have adverse effects on sexual behavior, territorial aggression, fertility and the reproductive system of the adult male rat.     

Aromatase inhibition blocks the activation and sexual differentiation of appetitive male sexual behavior in Japanese quail

Two experiments investigated the role of estrogens in the activation and sexual differentiation of appetitive sexual behavior (ASB) in Japanese quail (Coturnix japonica) as measured by a learned social proximity response. Injection of the aromatase inhibitor R767 13 in castrated, testosterone (T)-treated male quail completely suppressed ASB, confirming that, like consummatory sexual behavior, ASB is mediated by T aromatization. ASB is not observed in female quail, even if they are treated with T as adults. The role of embryonic estrogens in the sexual differentiation of ASB was tested by blocking estrogen synthesis in ovo. Control male and T-treated female quail deprived of estrogens during embryonic life learned the social proximity response used to assess ASB, whereas control female quail did not, despite the presence of high T. Thus, ASB is demasculinized by the action of embryonic estrogens during ontogeny as is consummatory behavior.