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J Recio

Publications and source records attributed to J Recio.

34 records · Page 2Linked to original sources
PubMed1996

Serotonergic modulation of photically induced increase in melatonin receptor density and Fos immunoreactivity in the suprachiasmatic nuclei of the rat.

The mammalian suprachiasmatic nuclei (SCN) contain a circadian clock which is regulated by neuronal photic and non-photic afferences. Among these, the serotonergic input originating from the dorsal raphe nucleus (DRN) is extremely important. In rats, a light pulse administered during the dark period is known to induce the expression of the immediate early gene c-fos and to increase melatonin receptor density in the SCN. The aim of this study was to assess whether, in rats, these two phenomena were regulated by serotonin, acting via 5-HT1A receptors. Three days after pinealectomy, 4 groups of rats were injected i.p. 90 min before sacrifice with respectively: (1) vehicle, (2) the 5-HT1A-agonist 8-OH-DPAT (5 mg/kg), (3) the 5-HT1A-antagonist NAN-190 (10 mg/kg) or (4) NAN-190 and the 8-OH-DPAT. Half of the animals from each group were exposed to light for 60 min before sacrifice and the other half remained in darkness. Sacrifice took place 5 to 6 h after lights off. Our results show that the antagonist NAN-190: (1) completely blocked the photically-induced increase of melatonin receptor density in the SCN, with an IC50 = 0.352 +/- 0.103 mg/kg, and (2) partially blocked (30%) the photic induction of Fos (the protein product of c-fos) in the ventrolateral subdivision of the SCN. The agonist 8-OH-DPAT enhanced the photically-induced increase of melatonin receptors by 10% and decreased the photically-induced increase in Fos by 18%. Both drugs were devoid of any effect in non-light exposed animals. From these results we may suggest that, in rats, there is a serotonergic control of the neuronal path driving photic information to the SCN. This regulation seems to occur through 5-HT1A or 5-HT1a-like receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Diurnal changes in the content of indoleamines, catecholamines, and methoxyindoles in the pineal gland of the Djungarian hamster (Phodopus sungorus): effect of photoperiod.

Previous studies in Syrian hamster have shown that the correlations between the daily fluctuations in the contents of pineal indoleamines and methoxyindoles are influenced by the photoperiod, and that dopamine may play a role in the regulation of pineal function. The present study investigated the 24 hour changes in the content of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), N-acetylserotonin (NAS), melatonin, 5-methoxytryptophol (5-MT), noradrenaline (NA), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC) in the pineal gland of female Djungarian hamsters exposed to long (LP; LD 16:8) or short (SP; LD 10:14) photoperiods for 10 weeks. Pronounced nocturnal increases of N-acetylserotonin and melatonin content were observed irrespective of the photoperiod regime. The content of 5-HT was markedly decreased during the first hour of the night in LP, which contrasted with the lack of changes in NAS and melatonin content at this time. In SP, an increased 5-HTP content and a less obvious decrease in 5-HT content was observed during the night, although melatonin and NAS content were even higher than in LP. Similar daily patterns as for 5-HT were observed in the 5-HT oxidative metabolites (5-HIAA and 5-MT). When considering values throughout the day, a poor correlation for 5-HT vs.. NAS and melatonin content was observed, which was particularly evident during the nighttime. These data indicate that the daily variation of pineal indoles may not only be dependent on changes in the N-acetyltransferase activity but also in other mechanisms regulating pinealocyte 5-HT availability. As previously reported in other species of hamster, pineal NA content did not show daily variations in LP conditions, although a nocturnal increase was detected in SP. In contrast, pronounced nocturnal increases were observed in the content of DA and its acid metabolite, DOPAC, irrespective of the photoperiod. These data indicate the existence of an increased dopaminergic turnover during the night and further support a role for DA in the regulation of melatonin synthesis and in the synchronization of the pineal functions.

Animals↗
PubMed1996

Daily and photoperiodic melatonin binding changes in the suprachiasmatic nuclei, paraventricular thalamic nuclei, and pars tuberalis of the female Siberian hamster (Phodopus sungorus).

Using quantitative autoradiography, 2-(125)I-melatonin binding was investigated throughout the light:dark cycle in the suprachiasmatic nuclei (SCN), paraventricular nuclei (PVT), and pars tuberalis (PT) of adult female Siberian hamsters kept for 10 weeks in either long or short photoperiods (LP or SP, respectively). Plasma melatonin concentrations were measured by radioimmunoassay, and the sexual status of the animals was established by visual inspection of vaginal smears and by weighing uteri after sacrifice. The SCN displayed neither daily nor photoperiod-dependent variations in specific binding. Melatonin receptors in these nuclei would be regulated neither by plasma melatonin nor by the light:dark cycle or sexual steroids. By contrast, melatonin receptor density in the PT displayed both strong daily (maximal values during the first half of the light period and minimal values during the night) and photoperiod-dependent (maximal values in LP) variations. These variations dependent on changes in the maximal binding (Bmax) without differences in the dissociation constant (Kd). Daily melatonin receptor densities in the PT of LP- and SP-exposed animals might be regulated by the dark:light transition but not by melatonin. Daily profiles of 2-(125)I-melatonin-specific binding in the PT were independent of photoperiod. Factors underlying the photoperiod-related variations presently are unknown. Concerning the PVT, weak variations in specific binding were detected in SP only when time points were grouped according to the light or dark periods. It is not yet possible to conclude whether they have any physiological relevance. These results show clearly that the regulation of melatonin receptors varies among structures (SCN, PVT, and PT) in the Siberian hamster and is also totally different from that found in the rat.

Analysis of Variance↗
PubMed1995

Daily variation in the content of indoleamines, catecholamines and related compounds in the pineal gland of Syrian hamsters kept under long and short photoperiods.

This study examined the diurnal changes in the content of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), N-acetylserotonin (NAS), melatonin, 5-methoxytryptophol (5-ML), noradrenaline (NA), dopamine (DA), and 3, 4-dihydroxyphenylacetic acid (DOPAC) in the pineal gland of Syrian hamsters kept under long (14L:10D) and short (10L:14D) photoperiods. The nocturnal increase in NAS and melatonin levels was dependent upon the prevailing photoperiod, with a prolonged duration when the night lengthened. In both photoperiods, NAS and melatonin contents increased several hours after the onset of darkness, and, in animals kept in short photoperiod, the levels of both compounds began to decrease before light onset. On the contrary, decreases were noted in 5-HT, 5-HIAA, and 5-ML contents during the night, which was directly proportional to the dark phase. 5-HTP levels did not show a rhythmic variation. Correlations between the mean values of 5-HT-related compounds showing daily rhythms were very high when group means were compared, but they decreased when values from individual animals were considered. In addition, when correlations were calculated on per-animal basis during the night phase, a weak negative correlation was found for 5-HT vs NAS and 5-HT vs melatonin, although the correlation of 5-HT with positively 5-HT-correlated compounds (5-HIAA and 5-ML) continued to be high. These results indicate that the nocturnal increase in the N-acetyl transferase activity is the major factor generating the rhythm of pineal 5-HT content, but that other photoperiod-dependent mechanisms (i.e., 5-HT synthesis or release) seem to be also implicated. On the other hand, this study shows that NA content in the Syrian hamster pineal gland does not exhibit daily variations, although marked nocturnal increases in the levels of DA and DOPAC were evident. These results suggest the existence of parallel daily alterations in pineal catecholamine synthesis and release, and suggest a role for DA in the pineal activation at night.

Animals↗
PubMed1994

Pharmacological profile and diurnal rhythmicity of 2-[125I]-iodomelatonin binding sites in murine mammary tissue.

Recent studies demonstrated that melatonin treatment decreased the growth of mammary glands in pubertal and pregnant mice. In vitro, melatonin inhibited murine mammary gland growth at microM concentrations and increased it at pM concentrations. Melatonin-induced changes of cyclic nucleotide synthesis was also demonstrated in mammary gland slices in vitro. The objective of the present study was to assess the possible existence of specific binding sites for melatonin in murine mammary gland by using 2-[125I]-iodomelatonin as a probe. The specific binding of 2-[125I]-iodomelatonin to murine mammary gland membranes was rapid, saturable, and reversible, showed an affinity in the low nM range, and displayed time, temperature, and pH dependence. Scatchard analysis indicated the existence of a single class of binding sites that exhibited a diurnal rhythmicity in affinity (Kd) and receptor density (Bmax). A maximum in Bmax (267 +/- 42 fmol/mg protein) was found at the light period, while affinity was maximal during darkness (Kd = 1.33 +/- 0.22 nM). In competition studies dopamine and dopamine-related agents, as well as 6-hydroxymelatonin and serotonin, but not melatonin, effectively displaced 2-[125I]-iodomelatonin from mammary binding sites. The results demonstrated a specific binding of 2-[125I]-iodomelatonin to murine mammary glands, with affinity in the low nM range, and a pharmacological profile that differed from that reported for 2-[125I]-iodomelatonin acceptor sites in other tissues.

Animals↗
PubMed1977

A two-year experience with cromolyn sodium in children with asthma.

A two-year experience with cromolyn sodium in children with asthma drawn from inner city population, is presented. Though the initial response to the drug at six weeks was excellent, the response over a two-year period was only very moderate. The possible reasons for this are discussed.

Asthma↗
PubMedDate not supplied

2-[125I]iodomelatonin binding sites in murine mammary tissue.

2-[125I]iodomelatonin binds in vitro to murine mammary gland membranes, in a specific, saturable, reversible and temperature-dependent and pH-dependent way, displaying an affinity within the low nM range. The order of affinity to displace the radioligand from mammary membranes was: 6-hydroxy-melatonin > 5-hydroxyindoleamines > noradrenaline > 6-chloromelatonin > 5-methoxyindoles (melatonin included). There was a diurnal rhythm in Kd and Bmax of 2-[125I]iodomelatonin binding, displaying the highest affinity and the lowest binding site concentration during the scotophase. The functional significance of melatonin binding sites was indicated by changes in binding parameters related to different rates of mammary growth during puberty, estrous cycle, pregnancy, lactation and the postlactation period.

Animals↗
PubMedDate not supplied

[Severe heart arrhythmia secondary to magnesium depletion. Torsade de pointes].

We report a case of torsade de pointe ventricular tachycardia in a patient with chronic magnesium depletion. The etiological aspects implicated this unusual cardiac arrhythmia are: the congenital long QT syndrome; bradycardia, either sinusal or due to atrioventricular block; ionic depletions: hypokalemia, hypocalcemia and hypomagnesemia; treatment with antiarrhythmic class AI drugs (quinidine-like agents), tricyclic antidepressants, phenothiazines and erythromycin; organophosphate poisoning. After ruling out other factors, we concluded that it was caused by hypomagnesemia on the basis of laboratory findings and the good response to replacement therapy. We then discuss the several types of therapy proposed for this arrhythmia; finally, we emphasize the major role of magnesium in myocardial repolarization.

Electrocardiography↗