Adriana Morales-Otal

Oleamide and anandamide effects on food intake and sexual behavior of rats

Oleamide is a lipid with diverse properties, including cannabinoid-like activity. For example, it induces the classic triad of effects attributable to these molecules: decrease in core temperature, hypolocomotion, and reduction in pain perception. However, as it binds to the cannabinoid receptors (CB1) only at high concentrations, it is not considered an actual endocannabinoid. In this study, we tested the effect of oleamide on food intake and sexual behavior and compared it to the effect induced by anandamide. Results indicate that oleamide and anandamide increased food intake during the 3h post-injection. In addition, anandamide but not oleamide induced changes in sexual performance. This study further supports the role of endocannabinoids in food ingestion and male sexual behavior and gives additional support to the notion that, although oleamide might not be an endocannabinoid, it shares some effects with them.

Sexual behavior of female rats in a multiple-partner preference test

In this study, sexually experienced female rats were tested in a multiple-partner preference test (MPPT) in which they were allowed to pace their sexual contacts with four sexually active males. Four cylinders, with a small hole through which only the female could move freely from one cylinder to another, were assembled forming in the center an empty compartment. An intact female was placed in the central compartment and a sexually active male in each cylinder. Female sexual behavior was analyzed throughout the estrus cycle in four consecutive days. Each daily test lasted 15 min. The percentage of exits after intromission or ejaculation was significantly higher than the percentage of exits after each mount. The female spent significantly longer time with one of the males. We designated this male as the preferred male (PM). Although in each of the 4 days studied, females spent significantly longer time with the PM, however, the male selected was not the same throughout the estrus cycle. The number of entries into the compartment of the PM was significantly higher and increased around proestrus. Compared to previous studies, pacing behavior was notably lower in the conditions of the MPPT. No significant differences were observed during the estrous cycle concerning the other parameters recorded. The present results suggest that the MPPT could be a good model to study partner preference in the female rat.

Masculine sexual behavior features in the Flinders sensitive and resistant line rats

The Flinders sensitive (FSL) and resistant (FRL) lines of rats have been selectively bred for their differences in cholinergic sensitivity. The FSL rats display hypersensitive responses to agonists of muscarinic receptors. In addition, the FSL rats display behavioral alterations that support the notion that this strain could be useful as an animal model of depression. These abnormalities include increase in rapid eye movement sleep, decrease of saccharin consumption after stress, and reduced exploratory behavior in a novel open field. On the other hand, sexual behavior is a pleasure-seeking behavior that should be altered in a mood disorder characterized by anhedonia. In the present study, spontaneous masculine sexual behavior features were analyzed, both during 30-min tests as well as during a satiety test. Results showed that, compared to outbred Sprague-Dawley (SD) rats, both the FSL and the FRL rats displayed some behavioral impairment, like a marked decrease of the ejaculatory frequency. During the satiety tests, both the FSL and the FRL rats became exhausted sooner than their SD controls. In addition to considering the present results in terms of alterations in specific neurotransmitter systems, endogamy is proposed as a possible source of the behavioral alterations.

Copulatory Pattern of Male Rats in a Multiple Partner Choice Arena

INTRODUCTION It has been demonstrated that testing conditions may influence sexual performance in many mammals, including male rats. We recently developed a multiple partner choice arena (MPCA) consisting of four acrylic cylinders placed in a cross pattern with one male in each cylinder. A sexually receptive female rat was introduced into the center of the MPCA and was allowed to choose a male to copulate with. The female showed a preference for one of the four males, remaining longer and copulating more times with it. AIM The study aims to evaluate and compare the copulatory pattern of male rats in two arenas: the standard arena (SA) and the MPCA. METHODS In Experiment 1, a group of 10 male rats mated in an SA (a closed cylinder) and 2 weeks later they mated in the MPCA, in order to compare different parameters of male sexual behavior. In Experiment 2, the sexual behavior of two different groups of sexually experienced male rats was tested in two conditions: the SA and the MPCA. In the latter, only the behavior of the preferred (P) males and nonpreferred (NP) males that ejaculated was recorded. MAIN OUTCOME MEASURES The main outcome is the number of intromissions preceding ejaculation and the latencies to mount, intromit, and ejaculate. RESULTS In Experiment 1, the number of intromissions was significantly reduced and the intromission and ejaculation latencies were significantly shortened when the males were tested in the MPCA rather than in the SA. In Experiment 2, both groups of males tested in the MPCA (P and NP) showed a significant reduction in the number of intromissions preceding ejaculation and shorter mounting and ejaculation latencies in comparison with rats in the SA. This decrease was more noticeable in NP males. CONCLUSIONS The MPCA reduce significantly the ejaculatory pattern in male rats.

Further Definition on the Multiple Partner Choice Arena: A Potential Animal Model for the Study of Premature Ejaculation

INTRODUCTION The multiple partner choice arena (MPCA) is an experimental setup in which male rats display a significant shortening of ejaculation latency, which is the main characteristic of premature ejaculation (PE) in men. Thus, the MPCA is a potential animal model for PE. AIM In this study, we further analyze whether the features of the MPCA satisfy the validity criteria for it to be considered an animal model as well as the possible participation of the serotoninergic system in the faster ejaculation exhibited by male rats in the MPCA. METHODS In Experiment 1, male rats were tested in a standard arena to assess their sexual behavior, then were assessed 1 week later in the MPCA. Another group was first tested in the MPCA, then in a standard arena. In Experiment 2, male rats divided into two groups were treated daily with WAY-100635 (5-HT(1A) antagonist) or vehicle for 15 days. In each group, half of the subjects were tested in a standard arena and half were tested in the MPCA on days 1, 8, and 15 of treatment. MAIN OUTCOME MEASURES Number of intromissions and intromission and ejaculation latencies were the main outcome measures. RESULTS In Experiment 1, males tested in the MPCA ejaculated significantly faster, regardless of the order in which they were evaluated in both arenas. In Experiment 2, the administration of WAY-100635 increased intromission and ejaculation latencies, and the number of intromissions in the MPCA. CONCLUSIONS The results obtained in the MPCA support its use as an animal model for PE evaluation.

Monoaminergic and cholinergic stimulation of masculine sexual behavior in neonatally demasculinized male rats.

Sexual behavior during adulthood largely depends upon hormonal events that take place around birth. Administration of the antiestrogen Tamoxifen (Tx) to males immediately after birth induces a marked decrease of masculine sexual behavior during adulthood. On the other hand, it is well known that masculine sexual behavior can be stimulated by the administration of drugs acting specifically on the monoaminergic or the cholinergic systems. This study was performed to analyze if masculine sexual behavior can be pharmacologically stimulated in adult male rats neonatally demasculinized by the administration of Tx. Neonatal administration of Tx induced clear impairments of masculine sexual behavior during adulthood. Administration of oxotremorine (OXO), 8-OH-DPAT (8-hydroxy-2(di-n-propylaminotetraline)), yohimbine (YH), and apomorphine (APO), drugs that normally elicit a stimulation of masculine sexual behavior were unable to fully restore it in demasculinized males. Only slight improvements of some behavioral parameters were observed with 8-OH-DPAT and YH. OXO seems to induce a worsening of sexual behavior impairments. Results obtained with APO were not significantly different from saline controls. Data suggest that neonatal treatment with Tx induces permanent impairments of the neural circuitry regulating masculine sexual behavior not only limited to morphological changes but also functional alterations of the neurotransmitter systems.

Sexual Behavior in Rats: An Animal Model for the Study of the Neuroendocrine System

Although the influence of gonads on sexual behavior has been empirically known for a number of centuries, it was not until the pioneering studies of Brown-Sequard and Steinach at the beginning of the twentieth century that this relationship was scientifically analyzed. Moreover, the clever experiments conducted by these researchers suggested the existence of humoral factors that regulate not only sexual behavior, but also the morphological characteristics that define gender.

Effects of neonatal treatment with two phytoestrogens on male rat sexual behavior and partner preference.

The aim of this work was to compare the effect of neonatal treatment with the phytoestrogens coumestrol (COU) and genistein (GEN), administered in equimolecular doses, on the sexual behavior and partner preference of male rats. Four groups of male rats were injected daily from day 1 to 5 with 150 µg of GEN, an equivalent amount of COU, 1 µg of &bgr;-estradiol 3-benzoato (EB), or olive oil (VEH) (control). A fifth group remained intact. In the GEN group, intromission and ejaculation latencies decreased, whereas ejaculatory frequency increased. Contrasting results were observed in COU males. EB males could not ejaculate and their mount and intromission latencies increased significantly. To determine sexual-partner preferences, a multiple partner preference arena was used and two types of tests were performed, the first one without allowing contact test (CT) with the stimulus animals, followed by a CT. COU and GEN groups did not show preference for any stimulus animal, whereas the EB males preferred the expert male. When CT with the stimulus animals was allowed, GEN-males preferred the receptive female, unlike the COU and EB groups. It is concluded that neonatal treatment with COU and GEN induced opposite effects, the effects of COU being more estrogenic.