Biomedical subjects

J L Valatx

Publications and source records attributed to J L Valatx.

At least 37 records · Page 2Linked to original sources

PubMed1996

Distribution of prolactin receptors in the rat forebrain. Immunohistochemical study.

The distribution of prolactin receptors (PRL-R) in the rat brain was investigated for the first time with the immunohistochemical technique using monoclonal antibodies raised against PRL-R purified from rat liver. Granular immunostaining was observed in neurons and along their dendritic processes and fibers. PRL-R like immunoreactive neurons were found in a number of brain areas. There was a very dense labelling in the cerebral cortex (pyramidal cell layer), septal nuclei, amygdaloid complex as well as in the hypothalamus (suprachiasmatic, supraoptic, paraventricular and dorsomedial nuclei). A dense staining was seen in the substantia nigra, habenula and in the paraventricular thalamic nucleus. Immunostaining was also found in the choroid plexus and in the subcommissural organ. Comparison between the present distribution and that of PRL-like immunoreactivity indicates that the density of PRL-R generally corresponds to that of the fibers. However, in some regions densely stained by PRL-R antibody, there are very few PRL-immunoreactive fibers. These results are suggestive of different modes of action of PRL in the brain.

Amygdala↗

PubMed1995

Sleep increase after immobilization stress: role of the noradrenergic locus coeruleus system in the rat.

In a preliminary study we showed that the sleep rebound occurring after sleep deprivation is decreased in rats treated with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), a neurotoxic agent specific for the noradrenergic cells of the locus coeruleus (LC). Sleep deprivation methods not only involve sleep loss, but also stress, which per se may induce an increase in sleep duration. Extensive research showed that the locus coeruleus is involved in stress. To evaluate the participation of LC in this mechanism, the effect of DSP-4 treatment was studied on sleep duration following a short intense stress in the absence of sleep loss. The results showed that the augmentation of sleep after 1 h of immobilization stress is lower in DSP-4-treated rats (slow-wave sleep duration, -24%; paradoxical sleep duration, -52%). These findings suggest that the increase in sleep induced by such a stressor is mediated, at least in part, by the noradrenergic LC.

Adrenergic Agents↗

PubMed1995

Corpus spongiosum penis pressure and perineal muscle activity during reflexive erections in the rat.

This experiment represents the first simultaneous analysis of corpus spongiosum of the penis (CSP) pressure and perineal muscle activity during reflex-induced penile erections in the awake rat and provides new data on the coordination of muscular and vascular events in erection physiology. Nine male Sprague-Dawley rats were implanted with pressure transducers under pentobarbital anesthesia (60 mg/kg) for use in a new technique of chronic erection recording involving simultaneous CSP pressure monitoring and electromyography (EMG) of the ischiocavernosus (IC) and bulbospongiosus (BS) muscles. The association of these physiological measurements with visually scored ex copula erectile events was investigated. Reflexive erectile events were systematically associated with an increase in baseline CSP pressure. Glans erections were associated with dramatic suprasystolic CSP pressure peaks concurrent with BS muscle bursts. Indeed, measures of CSP pressure and BS EMG activity were found to vary significantly with the intensity of glans erection. Flips of the penile body, however, involved small CSP pressure increases and IC bursts. These data demonstrate for the first time that both CSP pressures and perineal muscle activity vary significantly with the intensity of penile erection.

Animals↗

PubMed1995

Prolactin and rapid eye movement sleep regulation.

During the past few years data have accumulated suggesting the involvement of prolactin (PRL) in rapid eye movement sleep (REMS) regulation. Pituitary PRL secretion seems to be, at least in part, sleep-dependent. PRL is also found in the central nervous system. PRL-containing neurons in the hypothalamus project to various structures in the brain. Systemic injection of PRL promotes REMS in rats, cats and rabbits. Intracerebroventricular injection of PRL enhances REMS in rats. Stimulation of endogenous PRL secretion by vasoactive intestinal peptide (VIP) also promotes REMS. Immunoneutralization of blood-borne PRL slightly reduces REMS. Various observations (hypoprolactinemic and hyperprolactinemic rats) indicate that PRL may act on REMS via modulating the diurnal rhythms of REMS. It is likely that hypothalamic PRL is more important for sleep regulation than circulating PRL. Hypothalamic PRL is likely involved in the mediation of the REMS-promoting activity of VIP. We conclude that PRL has a role in REMS regulation.

Animals↗

PubMed1994

Experimental evidence of penile erections during paradoxical sleep in the rat.

We have developed a new technique to chronically monitor penile erections in the rat across behavioural states. This technique, involving chronic erectile tissue pressure monitoring and simultaneous ischiocavernosus and bulbospongiosus (IC-BS) muscle electromyography, demonstrates for the first time that rats exhibit penile erections during paradoxical sleep (PS). No erectile events were observed during slow wave sleep. These PS-related erectile events were similar to visually confirmed, waking state, erections in that they were associated with an increase in baseline erectile tissue pressure and, with IC-BS muscle bursts, dramatic suprasystolic penile pressure peaks often greater than 1000 mmHg. PS-related erections were 11 +/- 7 s in duration and were observed in 28.5% of all PS episodes. This method of chronic penile erection monitoring in the rat provides a new animal model for investigating neural mechanisms of sleep-related erections.

Animals↗

PubMed1994

Hypothalamic injection of prolactin or its antibody alters the rat sleep-wake cycle.

Several studies have suggested an interaction between prolactin and the sleep-wake cycle. In this study ovine prolactin (oPRL) and anti-prolactin antibody were microinjected into the rat dorsolateral hypothalamus, which contains prolactin-like immunoreactive neurons. Results indicate that during the light period, prolactin injection induced an increase in paradoxical sleep duration, whereas it caused a decrease when injected during the dark period. Anti-prolactin antibody injection during the dark period also decreased paradoxical sleep duration. There was no effect of oPRL or antibody on slow wave sleep duration irrespective of injection time. These results suggest that prolactin injection may have an inhibitory effect on hypothalamic prolactin neurons.

Animals↗

PubMed1993

Effect of prolactin on the sleep-wake cycle in the rat.

The purpose of this study was to examine the effects of prolactin on the sleep-wake cycle. Ovine prolactin was injected subcutaneous at a dose of 10 micrograms/animal or intra-cerebro-ventricularly at doses of 100, 10 and 1 ng/animal. The subcutaneous injections were given during either the diurnal or nocturnal period. Results indicate that oPRL decreases paradoxical sleep duration when injected during the dark period and increases it when injected during the light period. The i.c.v. injections were given only during the dark period and the effects were similar to those obtained with the s.c. injections. There was no effect on slow-wave sleep duration irrespective of injection time or injection site.

Activity Cycles↗

PubMed1993

Sleep and active cochlear micromechanical properties in human subjects.

In this paper the effect of sleep on the cochlea is studied by transiently evoked otoacoustic emissions (TEOAEs). Amplitude increases considerably (e.g., 4 dB) and the effect of a contralateral noise on the TEOAEs decreases during the night. These modifications can be related to sleep, although there is no link to electroencephalographic sleep stage. During sleep onset, the effect of contralateral noise disappears: this could correspond to a functional rest of the auditory pathway during that period.

Acoustic Stimulation↗

PubMed1993

Anatomical distribution of prolactin-like immunoreactivity in the rat brain.

The present study examines prolactin PRL-like immunoreactivity (PRL-LIR) in the rat central nervous system and describes the distribution of labeled perikarya and fibers using a specific antiserum to ovine PRL. This antiserum does not cross-react with molecules of the pro-opiomelanocortin (POMC) family and recognizes rat PRL. PRL-LIR cell bodies are found exclusively in the lateral hypothalamic area surrounding the fornix, especially dorsolateral to it. No labeled cells are detectable in any other part of the brain, including the arcuate nucleus. Labeled fibers are dispersed in almost all parts of the brain. Dense plexuses are observed in the hypothalamus, midline thalamus nuclei, bed nucleus of stria terminalis, raphe dorsalis, and locus coeruleus. There is no apparent decrease in the number of PRL-LIR cell bodies and fibers in hypoprolactinemic mutant rats or after hypophysectomy, suggesting that central PRL is synthesized in such hypothalamic neurons. Comparison of PRL and alpha-melanocyte-stimulating hormone immunostainings provides evidence that the PRL network is independent of those of POMC and melanin-concentrating hormone. The present results support the hypothesis of two independent PRL systems: one peripheral (pituitary gland) and the other cerebral. Concerning the functional role of brain PRL, its widespread projections suggest that PRL is involved in multiple regulations. The presence of PRL-LIR in brain areas involved in sleep-wake control is a strong argument for its role in such a regulation.

Animals↗

PubMed1993

[Prevalence of sleep and wakefulness disorders in high school students at the Academy of Lyon].

We studied sleep and wakefulness disorders in high schools of the Lyon district. Data were collected by auto-questionnaire from a very large sample (11,923 boys and 13,870 girls) of high school students, between 15 and 20 years of age. Thirteen per cent of boys and 17% of girls complained of poor sleep, and the most frequent trouble was difficulty in falling asleep. The difference between the length of the sleep during school time and holidays was greater than 3 hours for 24% of the students. About 10% of students who reported habitual difficulties in falling asleep used drugs (at least once a week) which facilitate sleep. The use of sleeping pills by the family correlated with that by the subject: 5% of boys belonging to families using sleeping pills are themselves users compared to 1% in the whole sample. Students using hypnotic drugs frequently had daytime naps (14% versus 3%); their morning wakefulness was poorer and their afternoon wakefulness better than students who did not.

Adolescent↗

PubMed1992

[Demonstration of prolactin messenger RNA after amplification in the brain in rats].

By means of immunocytochemistry, a central neuronal network containing a prolactin-like substance has been described in the rat. In order to demonstrate the synthesis of this peptide in these cells, we examined the presence of prolactin messenger RNA (PRL mRNA) in several brain samples including the pituitary gland. Amplification of the PRL mRNA was performed by the polymerase chain reaction technique, followed by southern blotting and hybridization with a specific oligonucleotide. Results showed the presence of the expected cDNA (468 bp) in the hypothalamus. Another cDNA with a lower molecular weight was also observed.

Animals↗

PubMed1990

[Sleep: current data in 1990].

Relations between serotonin and sleep have been re-evaluated in the waking and sleep periods. During sleep serotonin-containing neurons cease to function, as do all monoaminergic neurons. During waking one of the roles played by serotonin is to stimulate the synthesis of hypnogenic peptides. At the same time, serotonin inhibits paradoxical sleep as its occurrence during waking would be dangerous. In addition, under the influence of certain peptides serotonin, released by the dendrites of median raphe neurons, exerts a self-inhibition on their activity at the onset of sleep. The number of hypnogenic peptides discovered is ever increasing, raising the problem of their specificity and mode of action within the spontaneous sleep-waking cycle. Recent studies have reappraised the mechanisms of recovery after sleep deprivation. It is now believed that recovery is modulated by the intensity of stress during waking and not by the duration of waking, hence the hypnogenic role played by hormones, such as ACTH derivatives, that are involved in stress. Even more recent studies on the relationship between the mechanisms of sleep and those of central temperature are leading to a number of questions likely to modify the current hypotheses concerning sleep.

Histamine↗

PubMed1989

[Prolactin-secreting neurons in the dorsolateral hypothalamus in Sprague-Dawley rats].

By means of immunocytochemical techniques ovine prolactin like immunoreactivity (oPRL-LIR) has been demonstrated in the perikarya located around fornix in the dorso-lateral part of the rat hypothalamus. No PRL-LIR was observed in the arcuate n. perikarya. Immunoreactive fibers were present in the hypothalamus, medial thalamus, accumbens and amygdaloid nuclei.

Amygdala↗

PubMed1988

Hypophysectomy in monosodium glutamate-pretreated rats suppresses paradoxical sleep rebound.

Control untreated and pretreated female rats at birth with 10 injections of monosodium glutamate (MSG, 4 mg/g b. wt.) were hypophysectomized (HYPX) at 45-60 days of age and their sleep-waking cycle continuously registered. In control rats, hypophysectomy was followed by a 35.7% decrease in paradoxical sleep (PS) duration while it has no effect on the sleep of MSG-treated rats. After 24 h of PS deprivation, there was a normal immediate rebound of PS in the control HYPX and MSG rats while there was no significant rebound in the HYPX-MSG-treated rats. It is concluded that neuropeptides from arcuate nucleus and hypophysis are involved in a PS rebound mechanism.

Animals↗

PubMed1988

Effects of hypophysectomy on the sleep of neonatally monosodium glutamate-treated rats.

Monosodium Glutamate (MSG), known to induce neuronal cell degeneration of the arcuate nucleus of the hypothalamus, was subcutaneously injected (4 mg/g body wt.) at postnatal days 1 to 5 or 1 to 10 in female rats. Hypophysectomy was performed at 45-60 days of age. Sleep parameters were continuously recorded for at least 7 days. Results indicated that hypophysectomized (HYPX) NaCl-treated rats showed an increase of Slow Wave Sleep (SWS) (+29.6%) and a decrease of Paradoxical Sleep (PS) (-36.7%) durations. In MSG-treated rats, hypophysectomy did not alter SWS durations but it increased PS durations as MSG dosing increased. It was concluded that arcuate nucleus neurons seemed to be not critically involved in sleep production mechanisms.

Aging↗

PubMed1988

[Circadian rhythms of slow-wave sleep and paradoxical sleep are in opposite phase in genetically hypoprolactinemic rats].

In eleven genetically hypoprolactinemic rats (IPL nude rats) and five control rats (OFA), the sleep-waking cycle was continuously registered for 14 days at two ambient temperatures. At 23 degrees C, the slow wave sleep (SWS) duration of IPL rats was significantly higher (+6.8%, t = 5.4, p less than 0.001) than that of control rats, while the paradoxical sleep (PS) duration was lowered by 31.8% (t = 9.4, p less than 0.001). The circadian rhythm of PS disappeared while that of SWS persisted unchanged. At 30 degrees C, both sleep durations reached the level of control rats. The circadian rhythm of PS was however completely reversed: the PS acrophase was at 01 h while that of SWS was at 12 hrs. This first observation of spontaneous dissociation of the two states of sleep supports the hypothesis of two distinct circadian clocks, one for SWS, another for PS. It is suggested that hypothalamic prolactin and/or other still unknown genetic alterations might be responsible for the observed change in the PS circadian rhythm.

Animals↗

PubMed1987

[Absence of paradoxical sleep rebound in hypophysectomized rats pretreated at birth with sodium glutamate].

Control untreated female rats and rats pretreated at birth with ten injections of monosodium glutamate (MSG; 4 mg/g b.w.) were hypophysectomized (Hypox) at 45-60 days of age and their sleep-waking cycle continuously registered. After 24 hrs. of PS deprivation, there was an immediate increase of PS (rebound) in the control Hypox and MSG rats while there was no increase in Hypox-MSG rats. Factors from arcuate nucleus and/or from the hypophysis are probably involved in the mechanisms of PS rebound.

Animals↗

PubMed1986

Neonatal monosodium glutamate dosing alters the sleep-wake cycle of the mature rat.

Alterations of the sleep-wake cycle have been studied in male adult rats after neonatal administration of monosodium glutamate (MSG; 4 X 4 mg/g body wt.). Results indicated that MSG treatment caused: an almost complete disappearance of ACTH and alpha-MSH immunoreactive (IR) perikarya in the rostral part of the arcuate nucleus; an increase in total sleep duration with a more pronounced effect on paradoxical sleep. Regarding circadian rhythmicity there was a trend to a decomposition of the 24 h period into ultradian components (12 h, 8 h, 6 h harmonics). The participation of pro-opiomelanocortin peptides in sleep regulation is discussed.

Activity Cycles↗