Regulation Of Copulatory Behavior Research Articles

Effect of forebrain implants of testosterone or estradiol on scent-marking and sexual behavior in male and female rabbits

Chinning consists of rubbing the chin against an object, thereby depositing secretions from the submandibular glands. As mating, chinning is stimulated in male and female rabbits by testosterone and estradiol, respectively. To investigate the brain sites where steroids act to stimulate chinning and mating we implanted into the ventromedial hypothalamus (VMH) or the medial preoptic area (MPOA) of gonadectomized male and female rabbits testosterone propionate (TP; males) or estradiol benzoate (EB; females) and quantified chinning and sexual behavior. EB implants into the VMH or MPOA reliably stimulated chinning in females. Most of those implanted into the VMH and around half of the ones receiving EB into MPOA or diagonal band of Broca (DBB) showed lordosis. Chinning, but not sexual behavior, was stimulated in males by TP implants into the MPOA or DBB. Neither chinning nor mounting were reliably displayed by males following TP implants into the VMH. Results indicate that, in females, the VMH is an estrogen-sensitive brain area that stimulates both chinning and lordosis while the MPOA seems to contain subpopulations of neurons involved in either behavior. In males, androgen-sensitive neurons of the MPOA, but not the VMH, are involved in chinning stimulation but it is unclear if these areas also participate in the regulation of copulatory behavior.

EFFECT OF CHRONIC ACTIVITY WHEEL RUNNING ON MALE COPULATORY BEHAVIOR AND NEUROPEPTIDE Y GENE EXPRESSION IN RAT LOCUS COERULEUS AFTER OLFACTORY BULBECTOMY

Chronic activity wheel running in rates has been shown to improve male copulatory performance within an endogenous animal model of depression (Yoo et al., Psychobiology, 2000). The present study used the olfactory bulbectomy depression model to examine the effects of chronic activity wheel running and imipramine antidepressant treatment on copulatory behaviour and gene expression for prepro-neuropeptide Y (NPY) in brainstem locus coreuleus neurons. Male Long-Evans rats (45 d) were randomly assigned to the following conditions using a 2 × 2 × 2 design: bilateral olfactory bulbectomy or sham surgery voluntary activity wheel running or sedentary home cage daily imipramine or saline injections. After 21 days of treatment, animals underwent behavioral testing for copulatory activity. In situ hybridization histochemistry with autoradiography was used to measure levels of NPY messenger RNA (mRNA). Bulbectomized animals exhibited decrements in copulatory performance compared to sham animals. However, activity wheel running in bulbectomized animals improved copulation rates, reduced ejaculation latencies, and increased ejaculation frequencies. Activity wheel running after olfactory bulbectomy was also associated with elevations in NPY m RNA. Although NPY has been implicated in the regulation of copulatory behavior (Poggioli et al., Neuropeptides, 1990), further research is needed to determine whether adaptations in gene expression for NPY after chronic activity wheel running explain the enhanced male copulatory behaviors.

Site-specific effects of intracerebral injections of three neurokinins (neurokinin A, neurokinin K, and neurokinin γ) on the expression of male rat sexual behavior

Accumulating evidence indicates that neurokinins play a role in the neural regulation of male rat copulatory behavior. We have previously reported that injections of the neurokinin substance P into the medial preoptic nucleus facilitated male rat copulatory behavior. Recently, a number of other neurokinins, neurokinin K (neuropeptide K), neurokinin A (substance K), and neurokinin γ (derived from the same gene as substance P), have been indentified in the mammalian CNS. Therefore, in a series of experiments we examined the effects on male copulatory behavior following bilateral injections of different doses of neurokinin K (NkK), neurokinin A (NkA), or neurokinin γ (Nkγ) into the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BnST), or the caudate/putamen. Bilateral injections of NkK into the MPOA or BnST inhibited the expression of male copulatory behavior. The most marked effect was seen following bilateral injections of 0.25 and 0.52 nmol of NkK into the MPOA and the BnST. These injections produced a dramatic suppression of copulatory behavior in previously sexually vigorous male rats when compared to control injections. In contrast, bilateral injections of three different doses of NkA into the MPOA failed to affect any parameter of male copulatory behavior. Bilateral injections of 0.431 nmol of Nkγ into the MPOA failed to affect the expression of copulatory behavior, but significantly delayed its initiation when compared to controls. Bilateral injections of 0.251 nmol of NkK into the caudate/putamen had no significant effect on copulatory behavior in sexually vigorous male rats when compared to control injections. The results of the present study provide further support for a role of neurokinins in the regulation of copulatory behavior in the male rat. Taken together, these results suggest that the effects of neurokinins upon the expression of male copulatory behavior are site specific for brain regions in the sexually dimorphic vomeronasal pathway which includes the MeA, BnST, and MPOA.

Limbic regulation of copulatory behavior in male rats: A dual lesion study of the medial preoptic area and medial amygdala

Limbic regulation of copulatory behavior in male rats: A dual lesion study of the medial preoptic area and medial amygdala

Histofluorescent labelling of catecholaminergic structures in rotifers (Aschelminthes). II. Males of Brachionus plicatilis and structures from sectioned females.

1. Catecholaminergic structures in the male Brachionus plicatilis were investigated, using aqueous dansylpropranolol as fluorescent label of neurotransmitter receptors. 2. All major organs of the male are innervated by catecholaminergic systems, that may also be involved in the regulation of copulatory behavior. 3. Cryostat-sectioned preparations of the female B. plicatilis were also investigated. They provided additional information to findings on whole animals reported in our previous paper (Keshmirian and Nogrady 1987 a).

Inhibition of copulatory behavior in male rats by D-ALA 2-Met-Enkephalinamide

D-Ala 2-Met-Enkephalinamide (DALA), a synthetic analog of met-enkephaline resistant to enzymatic degradation, was injected intraventricularly to sexually experienced male rats paired with receptive females. A dose of DALA of 6 μg which did not influence spontaneous motor activity, completely suppressed the copulatory behavior of all animals tested. A dose of 3 μg significantly increase mounting and intromission latencies, but did not influence other measures of the copulatory behavior. The effect of DALA was prevented by naloxone (1 mg/Kg), a specific inhibitor of opioid receptors. The results suggest that enkephalins may play a role in the regulation of copulatory behavior.

Increased sexual behavior in the male rat following lesions in the mammillary region.

AbstractCopulatory output of the mature male rat was measured over an eight week period under conditions of each male having free access to a constant stimulus female.Of 71 males tested 31 of these (44%) had to be discarded as they did not reach our arbitrary minimum criterion of producing copulation plugs on 4 out of 14 nights during the initial (control) observation period. An extreme individual variability in sex drive was noted among the animals used for further testing.Employing equal sized groups of about ten animals and using a two week interval as the basic unit of time; the mean sexual activity for the group measured as number of copulation plugs found and mean percentage of nights on which copulation occurred indicated an extreme similarity of all groups. Maximum sexual response occurred during the initial 14 day test period and both measures of activity used (copulation plugs and days on which copulation occurred) declined by approximately 50% over the eight week test period.A similar 50% decline in response occurred following lesions in the middle hypothalamus dorsal to the arcuate nucleus or lesions dorsal to the hypothalamus involving the habenula and surrounding cortex. It was concluded these areas are not involved in regulation of copulatory behavior in the male rat.Lesions in the mammillary region (mostly medial) resulted in 50% of the animals showing a sustained constant copulatory output during the eight week test, while the remaining 50% (mostly with lateral lesions) showed marked increases which expressed as the mean of the group amounted to 90% copulation plugs and 50% in nights on which copulation occurred.Thus it was concluded that structures in the mammillary region at the junction of the diencephalon and mesencephalon normally exert a regulatory (inhibitory) influence on the sex drive in the male rat.