Dopamine release in the medial preoptic area is related to hormonal action and sexual motivation.

To help elucidate how general the role of dopamine (DA) release in the medial preoptic area (mPOA) is for the activation of male sexual behavior in vertebrates, we recently developed an in vivo microdialysis procedure in the mPOA of Japanese quail. Using these techniques in the present experiment, the temporal pattern of DA release in relation to the precopulatory exposure to a female and to the expression of both appetitive and consummatory aspects of male sexual behavior was investigated. Extracellular samples from the mPOA of adult sexually experienced male quail were collected every 6 min before, while viewing, while in physical contact with, and after exposure to a female. In the absence of a precopulatory rise in DA, males failed to copulate when the barrier separating them from the female was removed. In contrast, males that showed a substantial increase in mPOA DA during precopulatory interactions behind the barrier, copulated with females after its removal. However, there was no difference in DA during periods when the quail were copulating as compared to when the female was present but the males were not copulating. In addition, we show that precopulatory DA predicts future DA levels and copulatory behavior frequency. Furthermore, the size of the cloacal gland, an accurate indicator of testosterone action, is positively correlated with precopulatory DA. Taken together, these results provide further support for the hypothesis that DA action in the mPOA is specifically linked to sexual motivation as compared to copulatory behavior per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is sexual motivational state linked to dopamine release in the medial preoptic area?

The medial preoptic area (mPOA) is a key site for the dopaminergic enhancement of male sexual behavior. Dopamine release increases in the rat mPOA with mating, supporting the critical stimulatory role played by preoptic dopamine on male sexual behavior. However, it has been questioned whether dopamine is specifically related to the occurrence of male sexual behavior and not simply involved in general arousal. To address this question, we asked whether dopamine release in the mPOA is linked to the production of male sexual behavior in Japanese quail (Coturnix japonica), a species that exhibits a much shorter temporal pattern of copulation than rats and does not have an intromittent organ, resulting in a very different topography of their sexual response. Extracellular samples from the mPOA of adult sexually experienced male quail were collected every 6 min before, during, and after exposure to a female using in vivo microdialysis and analyzed using high-performance liquid chromatography with electrochemical detection. Extracellular dopamine significantly increased in the presence of a female and returned to baseline after removal of the female. However, quail that failed to copulate did not display this increased release. These findings indicate that it is not solely the presence of a female that drives dopamine release in males, but how a male responds to her. Furthermore, in quail that copulated, dopamine release did not change in samples collected during periods of no copulation. Together, these findings support the hypothesis that dopamine action in the mPOA is specifically linked to sexual motivation and not only to copulatory behavior or physical arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of medial preoptic–anterior hypothalamic lesions on development of sociosexual behavior in dogs.

Bilateral medial preoptic–anterior hypothalamic lesions in adult male dogs eliminate or impair copulatory behavior and reduce urine-marking responses but do not affect aggressive behavior. The present study examined the emergence of the adult forms of these same male sociosexual behavioral patterns when the lesions were made prior to puberty. 18 beagle puppies were allowed to interact with male peers during development. Ss with lesions had reduced frequency of juvenile mounting and an almost total absence of male copulatory activity in adulthood. Urine-marking and aggressive behavior in the juvenile and adult periods were not affected by the lesions. Findings reveal a sparing of function with regard to urine-marking but not sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localization in the amygdala of the amnestic action of diazepam on emotional memory

Electrical lesions of the medial preoptic area/anterior hypothalamus (MPOA/AH) have been reported to enhance the display of steroid-induced lordosis in castrated male rats. This study employed the cell body-specific neurotoxin, ibotenic acid, to ascertain whether neurons originating in this region (as opposed to axons of passage) tonically inhibit steroid-induced lordosis in adult male rats. Castrated, adult Long-Evans males received bilateral electrical lesions or injections of ibotenic acid or vehicle aimed at the MPOA/AH. Following administration of estradiol benzoate (EB) and progesterone, lordosis quotients (LQs) and lordosis ratings (LRs) were significantly higher in groups of rats with electrical lesions (LQ = 62.2 +/- 15.1; LR = 1.22 +/- 0.34) and ibotenic acid-induced lesions (LQ = 58.1 +/- 12.2; LR = 0.99 +/- 0.24) than in the control group (LQ = 12.8 +/- 7.3; LR = 0.22 +/- 0.13). To determine whether this enhancement of receptive behavior in MPOA/AH-lesioned males was an effect on estradiol-induced, as compared to progesterone-facilitated lordosis, groups of castrated rats in a second experiment received bilateral injections of ibotenic acid or vehicle aimed at the MPOA/AH and were tested for lordosis after administration of EB alone and again after injection of progesterone. Following treatment with EB alone, rats with ibotenic acid-induced MPOA/AH lesions tended to be slightly less receptive than control animals. However, following injections of progesterone, LQs and LRs were higher in the MPOA/AH-lesioned group than in the control animals, as had been observed in the first experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of precocial copulation in the domestic chick by progesterone brain implants.

Gave 86 2-wk-old Rhode Island Red * White Rock male chicks showing androgen-primed precocial copulation (a) progesterone implants in the medial preoptic area or other brain areas, (b) cholesterol brain implants, or (c) subcutaneous progesterone implants. Copulatory responding was suppressed by progesterone in the medial preoptic area, while such implants in other neural areas failed to induce sexual inhibition. Brain implants of cholesterol and subcutaneous progesterone did not inhibit copulatory activity. The suppression of sexual behavior was not accompanied by deficits in general activity or loss of weight. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female-enhanced aggression in male rats: Effects of genital anesthesia, castration, or preoptic lesions.

Male rats that had cohabited with ovariectomized females for 2 weeks became more aggressive toward male intruders after a novel estrous female had been placed in their home cages for a period of 4 hr on the previous day. No increase in aggression was seen in males exposed to anestrous females. Genital anesthesia did not attenuate the female-enhanced aggression effect. By contrast, no enhancement of aggression was observed in long-term castrated males after 24 hr of exposure to estrous females. Rats with bilateral electrolytic lesions in the medial preoptic area showed a normal female-enhanced aggression effect. The observations that exposure to females facilitates aggression in males subjected to genital anesthesia and in males with preoptic lesions raise the possibility that copulatory cues are not always required for the effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gonadal hormone activation of male courtship ultrasonic vocalizations and male copulatory behavior in castrated male deer mice (Peromyscus maniculatus bairdi).

Examined the influence of testosterone (T), a 5-alpha-reduced metabolite of T (dihydrotestosterone), and an aromatized metabolite of T (estradiol) on 35-kHz ultrasonic calling and copulatory behavior by 72 male deer mice. Daily treatment with T propionate (TP), dihydrotestosterone propionate (DHTP), or estradiol benzoate (EB) restored ultrasonic calling in long-term castrated Ss. Both TP and DHTP restored copulatory behavior, but EB was ineffective. Synergism of EB and DHTP action was observed; when subthreshold doses of EB (1 μg/day) and DHTP (50 μg/day) were administered in combination, ultrasonic calling and copulatory behavior were activated. In relation to other comparative findings, results indicate that the degree to which male sexual behavior is facilitated by 5-alpha-reduced androgens and/or estrogens is influenced by the species and the particular pattern of masculine behavior under consideration. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery of masculine copulatory behavior from lesions of the medial preoptic area: Effects of age versus hormonal state.

Two experiments tested the hypothesis that one consequence of the hormonal activation of the onset of copulation in male rats is a reduction in the plasticity of the medial preoptic area (MPOA) with respect to its role in copulation. In Exp I, 31 male rats received 1 mg of testosterone propionate daily from 10 to 45 days of age, and 30 Ss received oil injections. Ss in each of these groups received either bilateral MPOA lesions (MPOAX) or a sham operation as juveniles (28–31 days of age). The proportions of MPOAX Ss copulating as adults did not differ for Ss previously injected with oil or testosterone. In Exp II, 33 male rats were castrated at 15 days of age. These castrated Ss as well as 34 gonadally intact males received bilateral MPOA lesions or a sham operation in adulthood. Following testosterone replacement, MPOAX Ss displayed copulatory impairments regardless of hormonal state during development. Taken together, the results of these experiments suggest that the plasticity (with respect to copulation) of the neural system encompassing the MPOA is a function of some aspect of chronological age unrelated to the rat's developmental hormonal condition prior to the time of the lesion. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Contextual conditioning and the control of copulatory behavior by species-specific sign stimuli in male Japanese quail.

Three experiments were conducted to identify species-specific sign stimuli sufficient to elicit copulatory behavior in male Japanese quail and to determine how learning is involved in the control of behavior by these sign stimuli. In Exp 1, sexually experienced Ss were tested for copulatory behavior with a live female quail and with a model consisting of a female quail's head and neck mounted in front of a foam pad. Comparable levels of copulatory behavior were observed in the two tests, indicating that static visual cues provided by a female quail's head and neck are sufficient to elicit copulatory behavior in this species. Exp 2 showed that male birds that previously received numerous opportunities to copulate with a live female quail in the test situation were significantly more likely to copulate with the head?+?neck model than were sexually inexperienced Ss. Exp 3 showed that prior sexual experience with live quail facilitated responding to the head?+?neck model only if the sexual experience was provided in the same place where Ss were later tested with the model. This finding suggests that sexual experience facilitates control of copulatory behavior by species-specific sign stimuli through contextual conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal control of behavior in the Japanese quail.

Adult male and female Japanese quail were functionally castrated by exposure to a short photoperiod and then injected with either estradiole benzoate (EB) or testosterone propionate (TP). Females injected with EB (n = 24) exhibited normal sexual receptivity again but displayed no male courtship behavior. Males injected with EB (n = 10) showed both male and female copulatory patterns. Females injected with TP (n = 14) showed little sexual behavior of any sort, while males injected with TP (n = 10) displayed male sexual behavior. The male quail is thus more bisexual than the female. In contrast with mammalian species, the female is more bisexual. The difference is discussed in relation to the differences in the embryology and cytogenetics of birds and mammals. (29 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intermanual differences on motor and psychomotor tests in alcoholics: no evidence for selective right-hemisphere dysfunction

The effects of pharmacological manipulations of dopaminergic transmission on appetitive and consummatory aspects of male sexual behavior were investigated in castrated male Japanese quail treated with exogenous testosterone. Appetitive male sexual behavior was assessed by measuring a learned social proximity response and consummatory behavior was assessed by measuring copulatory behavior per se. The nonselective dopamine receptor agonist, apomorphine, inhibited in a dose-dependent manner both components of male sexual behavior. Two indirect dopamine agonists were also tested. Nomifensine, a dopamine re-uptake inhibitor, decreased appetitive sexual behavior but increased the frequency of mount attempts, a measure of consummatory sexual behavior. Amfonelic acid, a compound that enhances dopaminergic tone by a complex mechanism, increased aspects of both appetitive and consummatory behaviors. These data suggest that, in quail, as in rodents, increases in dopaminergic tone facilitate both appetitive and consummatory aspects of male sexual behavior. Apomorphine may be inhibitory in quail because it acts primarily on D2-like receptors, unlike in rats, where it stimulates sexual behavior and acts primarily on D1-like receptors at low doses but interacts with D2-like receptors at higher doses. This is supported by the observation that stereotyped pecking, a behavior stimulated selectively in quail by D2 agonists, was increased by apomorphine but not by the two indirect agonists. The observed partial dissociation between the effects of these dopaminergic agonists on appetitive and consummatory sexual behaviors suggests that these two components of male sexual behavior may be controlled by the action of dopamine through different neuronal systems.     

Appetitive as well as consummatory aspects of male sexual behavior in quail are activated by androgens and estrogens.

Appetitive male sexual behavior was measured in male quail with the use of a learned social proximity procedure that quantified the time spent by a male in front of a window providing a view of a female that was subsequently released into the cage, providing an opportunity for copulation. The learned response is not acquired by castrated males but can be acquired when castrates are treated with testosterone (T) or with the synthetic estrogen diethylstilbestrol or with the endogenous estrogen 17β-estradiol. Only birds that become sexually active acquire the response. Conversely, birds in which the consummatory copulatory behavior is disrupted by treatment with the antiestrogen tamoxifen lose the anticipatory response. These results demonstrate that appetitive sexual behavior is, like copulation, activated by T and by estrogens. This suggests that intracerebral aromatization of T also plays a critical role in the activation of this behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Systemic and intracerebroventricular injections of vasotocin inhibit appetitive and consummatory components of male sexual behavior in Japanese quail.

The authors investigated the behavioral actions of vasotocin (VT) in castrated testosterone-treated male Japanese quail. The appetitive and consummatory components of sexual behavior as well as the occurrence frequency of crows were inhibited, in a dose-dependent manner, by injections of VT. The authors observed opposite effects after injection of the V1 receptor antagonist, dPTyr(Me)AVP. Lower doses of VT were more active after central than after systemic injection, and effects of systemic injections of VT were blocked by a central injection of dPTyr(Me)AVP. The behavioral inhibition was associated with a modified diuresis after systemic but not central injection. These results provide direct evidence that VT affects male sexual behavior in quail by a direct action on the brain independent of its peripheral action on diuresis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of alpha-2 receptors in the medial preoptic area in the regulation of sleep-wakefulness and body temperature

The study was conducted on 48 free-moving male rats to find out the role of the medial preoptic alpha2 receptors in the regulation of sleep and body temperature. Recording electrodes for assessment of sleep-wakefulness, and injector cannulae for injection of drugs in the medial preoptic area were chronically fixed on the skulls of the animals. The noradrenergic fibres projecting to the medial preoptic area were destroyed in 24 rats by administration of 6-hydroxydopamine at the ventral noradrenergic bundle. Though arousal was produced in normal rats by the injection of the alpha2 adrenergic agonist, clonidine, at the medial preoptic area, it induced sedation in rats with noradrenergic fibre lesion. Clonidine did not alter the rectal temperature in normal rats but it induced hypothermia in lesioned rats. Injection of alpha2 antagonist, yohimbine, at the medial preoptic area induced sleep in rats with intact noradrenergic fibres. However, the sleep inducing effect of this drug was very much attenuated in the lesioned animals. There was no significant change in body temperature, in both these groups of animals, after yohimbine administration. The study indicates the role of presynaptic alpha2 adrenergic receptors in arousal response and indirectly supports the contention that the alpha1 postsynaptic receptors at the medial preoptic area are involved in hypnogenesis. It also suggests that the thermal changes induced by adrenergic system are mediated through alpha1 postsynaptic receptors. But the thermal changes do not contribute towards the induced alterations in sleep-wakefulness. It is proposed that there should be separate sets of noradrenergic terminals for regulation of sleep and body temperature.     

Differential effects of septal, preoptic, and habenula ablations on thirst-motivated behaviors in rats.

Two experiments used a total of 59 male Sprague-Dawley rats. Bilateral septal lesions dramatically enhanced barpressing rates generated under progressive ratio schedules of reinforcement. This increased barpressing was dependent on deprivation level but independent of the type of deprivation (i.e., food or water). Equivalent effects on barpressing were observed in Ss with bilateral medial forebrain bundle lesions at the level of the lateral preoptic area. Septal lesions, medial forebrain bundle lesions, and habenula lesions did not result in a hyperreactivity to bitter quinine solutions. Hyperreactivity to quinine was observed only in Ss with medial preoptic lesions. This medial preoptic lesion also impaired operant responding for water on a progressive ratio schedule of reinforcement. It is suggested that the medial preoptic lesion produced a deficit in thirst-motivated behavior. (16 ref) (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)     

Sexual fetishism in a quail (Coturnix japonica) model system: Test of reproductive success.

In the present study, the authors explored the reproductive consequences of fetishistic behavior in a previously developed animal model of sexual fetishism (F. K?ksal et al., 2004). Male domesticated quail (Coturnix japonica) received sexual conditioning trials in which a terrycloth object (the conditioned stimulus [CS]) was paired with the opportunity to copulate with a female quail (the unconditioned stimulus). Approximately half of the male quail came to copulate with the CS object and were considered to have developed fetishistic behavior. Each of the male quail was then tested with a female quail, whose eggs were incubated to determine rates of fertilization. The CS object was present for 30 s before and during the copulation test. Fetishistic male quail were slower to achieve cloacal contact with the female quail and showed less efficient copulatory behavior. However, they fertilized a greater proportion of eggs than nonfetishistic male quail. These results are unexpected from previous studies of the relationship between reproductive success and copulatory behavior and are discussed in terms of how fetishistic behavior directed toward an inanimate object may modify male-female interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The medial and lateral cell groups of the sexually dimorphic area of the gerbil hypothalamus are essential for male sex behavior and act via separate pathways

Male reptiles, birds and mammals do not copulate if the medial preoptic area (MPOA) is destroyed but the MPOA cell groups necessary for male sexual behavior were not known. Here, two cell groups essential for copulation are identified in the sexually dimorphic area (SDA) of the gerbil (Meriones unguiculatus) MPOA. Bilateral cell-body lesions of either the medial or lateral SDA eliminated mating in sexually experienced male gerbils given testosterone. Nearby MPOA lesions did not. The medial and lateral SDA affect sex behavior via separate pathways since lesioning the medial SDA on one side of the brain and the lateral SDA on the other did not stop sexual behavior.     

Atherogenic lipids and lipoproteins in hemodialysis patients

Different hypotheses have been put forward trying to explain the mechanisms associated with the disruption of male sexual behavior after lesions of the medial preoptic area (MPOA). It has been suggested that sexual motivation, motor execution or both are affected by MPOA lesions. In the present experiment, the socio-sexual behavior of male rats bearing extensive MPOA lesions, that abolished sexual behavior, was compared with that of sham-lesioned animals and to prelesion levels. The socio-sexual interactions were recorded for 10 min in one prelesion and two postlesion tests. The frequency and duration of the following behaviors were recorded: rearing, sniffing, self-grooming, grooming partner, genital exploration, pursuit and resting. The analysis of the socio-sexual interactions showed that the frequency and duration of pursuit was reduced in the first and second tests after the lesion in comparison to both prelesion levels and to a sham-lesioned group. There is strong evidence that pursuit is the only precopulatory behavior that can consistently predict the appearance of sexual behavior. When pursuit is reduced the transition from the precopulatory to the copulatory phase is made more difficult. Therefore, it appears that the MPOA lesions reduce the subject's motivation to engage in sexual behavior.