Biomedical subjects

J Marcó

Publications and source records attributed to J Marcó.

14 recordsLinked to original sources

PubMed1992

Effects of hyperprolactinemia on prolactin and LH pulsatile pattern in female rats.

Prolactin (PRL) and luteinizing hormone (LH) secretions are very closely-related. To further understand these mechanisms, the pulsatile secretion pattern of both hormones in experimentally-induced hyperprolactinemia has been studied in adult female rats. Hyperprolactinemia was induced by the transplanting of two pituitary glands. Nine days after the transplant operation, rats were bled (75 or 100 microliters/7 min for 3 h). Serum samples were analyzed for prolactin and LH values by RIA. Hyperprolactinemia modifies pulsatile PRL secretion by increasing the absolute amplitude and duration of the peaks together with a decrease in their frequency. Also, the mean values of the hormone during the whole studied period were increased. Hyperprolactinemia was followed by an increase in the mean values of LH and in the absolute amplitude of the peaks. All these results suggest that hyperprolactinemia induced by pituitary grafting in adult female rats, is followed by a significant change in prolactin and LH pulsatility, which may explain, to some extent, the effects of hyperprolactinemia on reproduction.

Animals↗

PubMed1991

Two-parameter mobile phase optimization for the simultaneous high-performance liquid chromatographic determination of dopamine, serotonin and related compounds in microdissected rat brain nuclei.

A new high-pressure liquid chromatography method with electrochemical detection is described that allows the simultaneous determination of dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid, 5-hydroxytryptophan and 5-hydroxyindoleacetic acid in microdissected nuclei from individual rat brains. No sample pre-treatment steps are required. Resolution and analysis time were optimized by a simple limited optimization procedure, involving two-parameter factorial design.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1991

Direct action of ethanol on pituitary prolactin secretion in vitro.

The effect of ethanol on prolactin release in vitro has been studied in order to investigate the direct action of ethanol on pituitary gland of the female rats. Animals were sacrificed in diestrus 2 and pituitary glands were incubated in TC-199 medium containing dopamine, noradrenaline, serotonin, TRH or cycloheximide with or without ethanol. The total amount of prolactin after the incubation period was calculated. Alcohol significantly increased the prolactin release in all groups. Cycloheximide and dopamine decreased the prolactin synthesis, but ethanol reduced the effect of dopamine. It is concluded that part of ethanol-induced hyperprolactinaemia, is due to a direct action of the alcohol on pituitary, affecting release and/or synthesis of prolactin.

Animals↗

PubMed1989

[Effect of progesterone and estradiol on the regulation of pulsatile secretion of LH in the various phases of the estrous cycle of rats].

The normal changes on LH pulse amplitude and frequency throughout the estrous cycle and the specific role of Progesterone (P) and Estradiol (E) on pulsatile LH release have been determined in rats at the different stages of the estrous cycle. The effects on pulsatile LH release 24 h after ovariectomy (OVX), have been studied, as well as the way the normal values of the pulsatile release was re-established, when the physiological levels of P and/or E were restored by implantation of either P, E, or both Silastic capsules in OVX rats 24 h early. Our data during the rat estrous cycle, have confirmed that the lowest pulsatile LH release was on estrus, and the largest LH pulses were obtained on diestrus day 1, when the plasmatic levels of both P and E were lowest. Moreover, a variable ovarian steroid effect has been found at the different stages of the cycle. In estrus and diestrus day 2, both steroids were necessary to restore the normal values of the pulsatile LH release in OVX rats 24 h before, while in proestrus, the main steroid was Estradiol, although a non steroidal ovarian factor was also necessary to restore the normal pulse amplitude. Finally, in diestrus day 1 there was an absence of an ovarian steroid negative feedback on pulsatile LH release, because the levels of both steroids were too low in this stage, to exert a regulatory role on pulsatile LH release.

Animals↗

PubMed1989

[Changes in the prolactin levels after administration of ethanol in diestrus 2].

The effect of ethanol administered at 18.00 h. of diestrus 2 on prolactin secretion has been studied in rats. Serum levels and pituitary content of prolactin were measured at 30, 60, 90 and 120 min. after administration of different doses of ethanol (0.5, 2 and 4 g/kg). Moreover, the variation of the prolactin release was determined at different hours of the rat estrous cycle, after administration of a single dose of ethanol (2 g/kg) at 18.00 h of diestrus. 2. Serum prolactin levels were significantly elevated after the preovulatory administration of ethanol with all the doses tested. The hyperprolactinemia appeared 60 min after ethanol treatment and the high prolactin levels were maintained during all the estrous cycles, especially in the proestrus day. The normal levels were re-established the 5th day after treatment. The ethanol produced a byphasic effect on pituitary prolactin content. During the first post-treatment hours, the pituitary prolactin concentration decreased with respect to the control group, but 24 hours after treatment, these values were increased and the normal concentration was restored 36 hours after treatment.

Animals↗

PubMed1985

Further evidence for effects of ethanol on gonadotrophins and prolactin secretion in female rats.

The effect of different doses of ethanol (0.5, 1.0, 2.0 and 4.0 g/kg) on LH, FSH and prolactin levels has been studied in female rats. Ethanol was administered in preovulatory periods (18 hr of diestrous or 9 hr of proestrous) and hormonal levels were measured at the 18 hr of proestrous. Ethanol administered at the 18 hr of diestrous produces a biphasic effect on serum LH levels. High doses of alcohol significantly decreased LH levels, whereas low doses (0.5 g/kg) increased the hormonal levels. When ethanol-treatment was at the 9 hr of proestrous, it only decreased LH levels with the dose of 4.0 g/kg. Serum FSH levels were unaffected by the preovulatory administration of ethanol. Serum prolactin concentrations were significantly elevated after i.p. administration of ethanol at the 18 hr of diestrous and the 9 hr of proestrous. The hyperprolactinemia is more pronounced in the rats treated at the 9 hr of proestrous. The results of these studies suggest that the ability of ethanol to modify LH and prolactin levels is due to a central depression caused for alcohol. These effects of ethanol could be mediated by the hypothalamic releasing factors and/or could be due to a direct action on the pituitary function. The sum of these effects produces important failures of the reproductive function in the female rat.

Animals↗

PubMed1979

[Modification of the ovarian cycle, ovulation and reproduction in rat by administration of p-chlorophenylalanine in the pre and post ovulation period (author's transl)].

The effect of p-Chlorophenylalanine (PCPA) administered in pre and post-ovulation phases on ovulation reproduction and ovarian cycle was studied in rats. Vaginal smears, number of ovules, mature follicles and ovaric histologic features were evaluated. PCPA administered in the periods after follicular rupture prolongs the diestrus phase from 2 to 10 consecutive days and totally inhibits the reproductive conduct. When administered in the periods just prior to follicular rupture, PCPA prolongs the estrus phase from 2 to 4 consecutive days and does not totally inhibit reproduction. A progressive increase in reproduction took place as treatment time approached ovulation, to such an extent that the number of inseminated and fertilized rats when treated at the ninth hour of the proestrus phase, was superior to the control group. PCPA administered in periods after and before follicular rupture totally inhibits ovulation in all cases. Ovaries present many mature follicles, as many as in the controls sacrificed at the 18 hour of the proestrus, just before ovulation.

Animals↗

PubMed1979

[Supression by copulation of the inhibitory effect of p-chlorophenylalanine on rat ovulation (author's transl)].

The effect of copulating on reflex ovulation was studied in rat. The effect of PCPA (300 mg/kg, i.p.) on ovulation and reproduction was compared by evaluating number of oocytes in tubes, histologic features of ovaries, vaginal cycle, insemination, fertilization and number of embryos per rat. PCPA, administered on 9th and 16th h of the estrus phase, totally inhibits ovulation, stimulates reproductive behaviour and prolongs the estrogenic phase. When the animals are kept in copulatory conditions for 16 or 46 hours, the inhibition induced in ovulation disappears to the extent that 60% of the rats become pregnant though the number of embryos is under that of the control group. The farther the treatment with PCPA within the same cycle in the ovulatory period, the greater the inhibitory effect on ovulation is and the lesser the neutralizing effect produced by reflexes related to copulation. Administration of PCPA at the 16 hour of the diestrus causes a greater increase in the average number of embryos-as compared to administration at the 9 hour. In periods longer than 48 hours before ovulation, the inhibition brought about by PCPA is not suppressed by copulatory conditions kept for 16 or 24 hours and is only neutralized if they are kept during a complete cycle. Those treated with PCPA in the diestrus phase and maintained in copulatory conditions for 46 hours, present a higher average of embryos than those maintained in similar conditions for 16 hours.

Animals↗

PubMed1978

[Reflex factors that modify the effect of p-chlorophenylalanine on ovulation and reproduction in rats (author's transl)].

The appearance of reflex ovulation in rats under the influence of the copulation, has been studied. Evaluation of insemination, fecundation, number of embryos, ovarian cycle and ovulation in several groups of rats treated with doses of p-CPA (300 mg/Kg, i.p.), have been made. The application of p-CPA 48 hours before the estrus phase, inhibits the ovulation. This increases significantly through copulation. Reproduction is totally inhibited by p-CPA in animals under copulation conditions during 24 hours of the estrus phase. The inhibition is desappears if placed under copulation conditions during a full cycle. Inseminated rats had a 33% decrease in number of embryos with respect to the control group. The application op-CPA 24 hours before the estrus phase does not produce any inhibition effect. The decrease observed in the number of embryos is non-significant. When p-CPA is applied, instead, 48 hours before the estrus phase, there is total inhibition of the reproductive conduct.

Animals↗

PubMed1976

[Serotoninergic mechanisms in ovarian cycle (author's transl)].

Influence of 5-HT on the rat follicle rupture mechanism was studied by the administration of p-clorophenyl-alanine (p-CPA) (300 mg/kg) at different stages of the ovarian cycle. The ovarian cycle of treated rats was subject of investigation, as well as the histology of tubes and ovaries. Administration of p-CPA at 10 hours of metestrus phase induces an inhibition of ovulation. Predominant diestrus phases in the ovarian cycle and luteinitation of ovaries suggested an increase in progesterone secretion probably owed to a correspondingly greater prolactine secretion. Adequate 5-HT levels in central structures proved to necessary for normal ovulation.

Animals↗

PubMed1976

[Effect of p-chlorophenylalanine on rat reproduction under different conditions of lighting (author's transl)].

Reproduction in female rats kept on artificial cycles of light/darkness, continuous lighting and continuous darkness, has been studied. Three weekly doses of p-chlorophenylalanine (p-CPA), 100 mg/kg, were given to half of the rats in each group during the two preconditioning months before copulation. An evaluation has been made of the insemination, fecundation, number of embryos, ovarian cycle and level of 5-HT in the hypothalamus. The administration of p-CPA had an inhibitory effect on the reproductive behavior, especially pronounced in rats kept under continuous lighting and under continuous darkness. The difference in 5-TH levels were greater among the groups kept on cycles of light/darkness without treatment and with p-CPA (0.05 greater than P greater than 0.01). The importance of 5-HT in the mechanisms of reproductive behavior is emphasized.

Animals↗

PubMed1975

[Effect of 6-hydroxydopamine intracerebrally injected on reproduction in rats (author's transl)].

The effect of 6-hydroxidopamine (6-OH-DA) --250 mug-- intracerebrally injected on rat ovulation has been studied. Administration of 6-OH-DA in the nucleus accumbens septi and its heigbhourhood, inhibited follicle rupture, causing ovarian cycles with leucocitary phases in nearly all cases. The ovaries present a deep lutteynitation. Administration of 6-OH-DA in the strio-hypothalamic tract gives rise to a estrogenic cycle and to a normal number of oocytes in the tubes. The study of the fibrillar degeneration leads us to assumption of a probable adrenergic connections of the nucleus accumbens septi with the lateral hypothalamic area, preoptic area and olfactory tubercule. The influence of the nucleus accumbens septi on the mechanisms of follicle rupture is stressed.

Animals↗

PubMed1975

[Effect of p-chlorophenylalanine on the reproduction of the rat (author's transl)].

The effect of p-chlorophenylalanie (p-CPA) --300 mg/kg-- on reproduction has been studied in the female rat. Groups of animals were injected with a dose of 300 mg/kg of p-CPA 48 hours before proper copulation conditions at different moments along the ovarian cycle. Presence of spermatozoa in the vaginal frotis was negative in treated rats; in the control groups however, positivity was found in variable proportions according to the phase of the ovarian cycle: 30 ad 90% in diestrus and proestrus respectively. Treated animals showed continuous diestrus phases and diffuse luteinitation of the ovary. The results may indicate that a decrease of cerebral 5-HT, caused by p-CPA, lessens the reproductive behaviour of the female rat through mechanisms depending probably on the liberation of gonadrotrophins.

Animals↗

PubMed1975

[Serotoninergic and adrenergic factors influencing the ovulation and reproduction in the rat].

The action of 5-hydroxytryptamine (5-HT) on ovulation and reproduction in female rats with unique or repeated treatments of p-chlorophenylalane (p-CPA) was studied under different conditions of illumination. Histological studies were carried out on the tube and ovaries, controls of the ovarian cycle and of inseminations produce by vaginal deposits. An evaluation has been made of the insemination, fecundation, number of embryos, ovarian cycle and in anothers series hypothalamic determinations of 5-HT were carried out. In one group of rats the effect of intracerebrally administration (n. accumbens septi) 6-hydroxydopamine (6-OH-DA) (250 mug) on ovulation was studied. The administration of a unique doses of p-CPA (300 mg/Kg) induces an inhibition of the reproductive cycle in all its phases and in all the rats. Which repeated doses (100 mg/Kg) reproduction was inhibited in rats maintained under continuous illumination and under continuous darkness. Ovulation studies revealed that follicle rupture, was inhibited with a unique dose of p-CPA (300 mg/Kg). The histological study showed, marked luteinitation of ovaries. The ovarian cycle after a unique dose of p-CPA showed continuous diestrus phases. The results may indicate that a decrease of cerebral 5-HT producing a hormonal change which leads to the disappearence of the oestrogenic phase, with consequent inhibition of rupture and decrease in receptivity of the female rat. The administration of 6-OH-DA in the n.accumbens septi inhibited follicle rupture giving rise to manifest lutteynitation. A further study on the degeneration of nerve fibres, suggests the posssibility of adrenergic influence in ovulation of septal structures.

Animals↗