Search PubMed⌕ Search

Biomedical subjects

M Mas

Publications and source records attributed to M Mas.

At least 73 records · Page 4Linked to original sources
PubMed1988

Stimulation of opioid receptors suppresses penile erectile reflexes and seminal emission in rats.

The effects of several doses of morphine and naloxone, given alone or in combination, on ex copula tests for rat penile erectile responses and seminal emission were studied. Morphine (0.1, 0.5, 1 and 5 mg/kg IP, 30 min before the test) reduced the proportion of animals showing erections in a dose-related fashion. Seminal emission was apparently more sensitive to opioid inhibition than erectile responses, since it was virtually suppressed by all the doses of morphine tested. Naloxone given alone (0.1, 1 and 10 mg/kg IP, 15 min before testing) was largely ineffective on these genital responses although a significant decrease in the display of erection was observed with the lowest dose. Naloxone (1 mg/kg) efficiently antagonized the effects of morphine (1, 5 and 25 mg/kg) on erectile responses and all but the largest dose of the opiate agonist on seminal emission. These results indicate that, in addition to the well-documented effects of opioids on sexual drive, their effects on the genital reflex potential could play a major role in the sexual deficits associated to opiate intake.

Animals↗
PubMed1987

Gonadal influences on spinal cord and brain monoamines in male rats.

Concentrations of norepinephrine (NE), dopamine (DA), 3,4-dihydroxy phenylacetic acid (DOPAC), serotonin (HT) and 5-hydroxyindoleacetic acid (HIAA) were measured by high-performance liquid chromatography-electrical detection (HPLC-ED) in homogenates of lumbosacral spinal cord, mediobasal hypothalamus and cerebral cortex of male rats. The effects of castration and testosterone propionate (TP) (20 micrograms/day X 2 days) were compared. Castrated animals had the highest levels of DA and DOPAC in the cerebral cortex and NE, HT and HIAA in the spinal cord, as well as decreased hypothalamic DOPAC. Testosterone treatment returned spinal cord monoamine concentrations to intact control levels. These findings point to the spinopetal monoaminergic pathways as sensitive targets for androgen action.

Animals↗
PubMed1987

Regional changes of brain Na+,K+-transporting adenosine triphosphatase related to ovarian function.

Synaptosomal Na+,K+-transporting ATPase activity of the mediobasal hypothalamus (MBH), the medial preoptic-suprachiasmatic (POSC) region and cerebral cortex was measured in rats at different stages of the estrous cycle and after ovariectomy and estradiol replacement. Enzyme activity of the MBH and POSC showed cyclic changes. In both regions it increased shortly before the proestrus surge of LH. However, the two areas responded to castration and estrogen treatment in an opposite fashion. No changes were detected in enzyme activity in the cerebral cortex. These findings are consistent with previous reports on cyclic changes in electrical activity and suggest that Na+,K+-ATPase activity could be a useful indicator of neural activity for the study of neuroendocrine interactions.

Animals↗
PubMed1987

Androgens stimulate preoptic area Na+,K+-ATPase activity in male rats.

This paper describes the effects of castration and testosterone replacement on the Na+,K+-ATPase activity levels of the cerebral cortex (CC), preoptic-suprachiasmatic region (POSC) and mediobasal hypothalamus (MBH) in male rats. Na+,K+-ATPase activity was estimated as the ouabain-sensitive fraction of ADP and AMP generation rate, measured by high-pressure liquid chromatography (HPLC) with UV detection, from a standard incubation mixture containing 3 mM ATP. Orchidectomy, performed 4 weeks before sacrifice, decreased ATPase activity of MBH. Testosterone propionate treatment (50 micrograms/day X 2 days) to castrated animals resulted in a 4-fold increase in enzyme activity in the POSC, an effect that might be related to the behavioral effects of androgens. None of the treatments seemed to influence the enzyme activity of the cerebral cortex.

Aggression↗
PubMed1987

Chlordiazepoxide facilitates erections and inhibits seminal emission in rats.

Two experiments have been conducted to clarify the effects of the benzodiazepine chlordiazepoxide (CDP) on the different components of male rat sexual behavior. In the first experiment the effects on penile erectile reflexes (PR) of two doses (10 and 30 mg/kg, IP) of CDP were compared with those of vehicle, no-treatment and baseline pre-test in a repeated measures design. In the second experiment the different components of male sexual behavior - PR, mating behavior and spontaneous seminal emission SSE) - were extensively studied after vehicle, 3 and 30 mg/kg CDP treatments. CDP was found to increase significantly the percentage of rats showing penile reflexes, enhance the number of erections per test and shorten the latency to onset of reflexes. It lowered the percentage of animals displaying seminal emission during the PR test. In the mating behavior test, CDP abolished copulatory (and other) behavior at 30 mg/kg. It decreased the number of animals achieving ejaculation at the subataxic 3 mg/kg dose level. In the SSE 3-day test, CDP significantly reduced the weight and the number of plugs of seminal material emitted by the CDP-injected animals. The possible involvement of the serotonergic system in determining the dose-dependent increase in erections and decrease in seminal emission following CDP treatments is discussed. Clinical implications are also briefly considered.

Animals↗
PubMed1987

Neurochemical correlates of male sexual behavior.

This report presents evidence of changes in the concentration of monoamine neurotransmitters and their metabolites in homogenates of spinal cord and brain areas of male rats related to specific events of their mating behavior. Intact male rats were allowed to copulate with receptive females and decapitated immediately after either the first intromission or the first ejaculation. Non-mating control animals were exposed to other males, instead of females. The concentration of monoamines (norepinephrine, dopamine and serotonin) and some of their major metabolites (DOPAC and HIAA) in homogenates of discrete brain areas (parietal cortex, preoptic region, mediobasal hypothalamus) and lumbosacral spinal cord were measured by HPLC-ED. Results suggest that sexual arousal is associated with both increased dopaminergic activity in the preoptic region and inhibition of descending monoaminergic signals to the lumbosacral cord, whereas ejaculation is accompanied by increased activity of the serotonergic, as well as dopaminergic, innervation of the preoptic region. These findings give neurochemical support to notions of central monoamines involvement in sexual behavior suggested by previous pharmacological studies.

Animals↗
PubMed1985

Stimulation of spinal serotonergic receptors facilitates seminal emission and suppresses penile erectile reflexes.

Penile erection and ejaculation are produced by spinal reflexes subject to tonic control from the brain. This study examines the possible involvement of serotonergic transmission in the supraspinal modulation of such reflexes. The effects of two drugs which facilitate serotonergic transmission by different mechanisms, namely the direct receptor agonist, 5-methoxy-N,N'-dimethyltryptamine (5-MeODMT), and the reuptake inhibitor, zimelidine, were compared in intact and spinal rats. Results show that serotonergic stimulation in intact rats by either drug produces a dose-related increase in the incidence of seminal emission as well as a definite decrease of the display of erectile responses. In the spinal animals 5-MeODMT treatment reproduced both effects. By contrast, zimelidine, which needs functional nerve endings to exert its agonistic action, was ineffective in the spinal rats. This is interpreted to exclude a peripheral mechanism for the effects of the serotonin agonists on penile reflexes of intact animals and makes a strong case for a spinal site of action. We postulate the existence of serotonergic receptors located in the lower segments of the spinal cord which, when stimulated, trigger seminal emission and suppress erection.

Animals↗
PubMed1984

Pineal indols and testosterone affect exploratory activity of male rats.

The testosterone level has an inverse relation to activity in the open-field test. This is more important in red light than in white light. Pineal indols do not disturb this action. Some of these results are consistent with the assumption that androgens play a role on the exploratory activity of adult subjects.

Animals↗
PubMed1984

Different roles of catecholaminergic and serotoninergic neurons of the medial forebrain bundle on male rat sexual behavior.

The medial forebrain bundle (MFB) plays an important role in the central elaboration of male sexual behavior. However the role of its ascending monoaminergic systems is not well understood. By selective lesions of catecholaminergic and serotoninergic axons of the MFB, produced with 6-OHDA and 5-7-DHT respectively, its possible involvement in male sexual behavior was studied. The evaluation of the behavioral patterns was studied by means of a microcomputer which also permitted the quantification of sequences in the sexual behavior patterns. Lesions with 5-7 DHT increased the intromission-ejaculation sequences and the percentage of ejaculatory males, without modifying other behavioral tests. Lesions with 6-OHDA diminished the number of "active" sexual patterns and motor activity. In order to check the specificity of the chemical lesions, the in vitro uptake of labeled norepinephrine and serotonin was measured, 5-7 DHT lesioned rats show a reduction in the uptake of 5-HT-C14 in the MPOA while 6-OHDA group show a reduction of NA-H3 in the striatum.

Animals↗
PubMed1984

Effects of monoamine neurotoxins injected in different brain areas on gonadotropin and androgen secretion in the male.

In order to investigate the relative contribution of the serotoninergic and catecholaminergic innervation of different brain structures to the control of gonadotropin secretion in the male, adult rats were given bilateral injections of the selective neurotoxins, 5,7-dihydroxytryptamine and 6-hydroxydopamine, into the mediobasal hypothalamus, the medial preoptic area, the amygdala, and the medial forebrain bundle. Serum levels of luteinizing hormone (LH), follicle-stimulating hormone, testosterone, pituitary follicle-stimulating hormone, and LH content were measured 15 days later. The medial preoptic area 5,7-dihydroxytryptamine injections were followed by 2- to 3-fold increases of serum LH and testosterone levels and pituitary LH concentration. The 6-hydroxydopamine injections in the medial forebrain bundle resulted in a 60% decrease of pituitary LH content, associated with serum levels of LH and testosterone which were lowered, although not significantly. None of the treatments seemed to influence either serum or pituitary concentrations of follicle-stimulating hormone. These results suggest a hitherto undocumented major function of the serotoninergic innervation of the medial preoptic area in the control of LH secretion in the male and confirm previous reports indicating that some of the catecholaminergic fibers carried by the medial forebrain bundle can be modulatory for LH secretion.

5,6-Dihydroxytryptamine↗
PubMed1981

The phospholipase A2 from human platelets.

Studies on a purified phospholipase A2 (PLA2) from human platelets show that the enzyme, which is copurified with the plasma membrane fraction, has a MW of approximately 50 K Dalton, requires Ca++, and has a pH optimum of 9.4. Under optimal conditions, PLA2 activity corresponds to at least 13 nmol/min/10(9) platelets. Unsaturated PL are preferred substrates and the enzyme is considerably more active on the aggregated form of the substrate than on the monomers. The specific activity is markedly affected by the quality of the interface, showing variations of more than 10-fold between different substrate forms. In the absence of detergents, a 4-fold increase in rate is observed when both products are present. Maximal rates are obtained at 20 mole percent of products to substrate. 1,2-Diglyceride and phosphatidic acid stimulate the hydrolysis of PC by the purified enzyme, however, in these forms of the substrate, neither of them are hydrolyzed. Activation of this enzyme by some intermediate of the phospholipase C pathway might play a role in the stimulus-linked release of platelet arachidonic acid.

Arachidonic Acid↗
PubMed1979

Lactate dehydrogenase isoenzymes of the hypothalamus, limbic structures, and the anterior pituitary during the estrous cycle.

Lactate dehydrogenase (LDH) and its isoenzyme (ISO) pattern were measured in the hypothalamus (HYP), amygdala (AMYG), hippocampus (HIP), cerebral cortex and anterior pituitary (PIT) of adult female rats sacrificed at different estrous cycle phases. The HYP, the AMYG and the PIT showed their maximal LDH values at proestrus and the lowest at diestrus. Those of the HIP showed the opposite pattern. The study of the ISO distribution pattern indicated that the cyclic variations of pituitary LDH activity were mainly due to changes of the ISO rich in A subunits, while in the B type they remained constant. By contrast, the cyclic changes of total LDH activity of all the brain structures studied were due to well balanced variations of both A and B subunits.

Amygdala↗
PubMed1978

Increase in pituitary levels of luteinizing hormone and follicle-stimulating hormone after pinealectomy in both intact and castrated male rats.

Twenty-eight-day-old male Wistar rats were pinealectomized and/or castrated. Animals were killed 26 days later and anterior pituitaries were dissected out, weighed, and their content of LH and FSH measured by RIA. Pinealectomized rats showed higher body weights than sham-operated animals, which suggests an inhibitory influence of the pineal on growth. The weights of pituitaries were increased by both pinealectomy and castration. However, in pinealectomized rats, but not in castrated, the elevated pituitary weights seemed to be due to the high body weights of those animals. The pituitary content and concentration of LH and the content of FSH were increased by pinealectomy in both intact and castrated rats. This finding may suggest that the pineal gland exerts an inhibitory action on the hypothalamic-pituitary axis that seems to be independent of the testicular function.

Animals↗
PubMed1978

Antiandrogenic effects of the pineal gland and melatonin in castrated and intact prepubertal male rats.

In castrated prepubertal rats, pinealectomy enhanced the testosterone-induced growth response of the seminal vesicles and melatonin inhibited this effect in a dose-related manner. In entire animals, the serum concentration of LH was increased after pinealectomy with no significant changes in other parameters. Administration of melatonin to intact, pinealectomized rats did not affect the serum concentrations of LH or testosterone but caused a dose-related decrease in the weight of the seminal vesicles. The highest dose of melatonin tested reduced the weight of the ventral prostate gland and the uptake of radioactivity by both the ventral prostate gland and the testes after injection of [5-3H]uridine. It is suggested that the pineal gland and melatonin may exert an antagonistic effect on the biological activity of androgens administered to castrated rats and that melatonin can reduce the growth of the accessory sex organs of intact, pinealectomized rats, in spite of a high concentration of LH in the serum. The well-known inhibitory influence of systemically administered melatonin on the accessory sex organs in male rats may be due to its antagonistic effect at a peripheral level.

Animals↗