D. P. Cardinali

Diurnal changes in melatonin binding sites of hamster and rat brains. Correlation with neuroendocrine responsiveness to melatonin

A diurnal variation in neuroendocrine sensitivity to melatonin is known to occur in hamsters and rats. The present experiments were carried out to examine the possibility that affinity and/or number of melatonin binding sites in brain could change accordingly at the two times when exogenous melatonin is known to be ineffective or effective to produce neuroendocrine changes, i.e., at 07 : 00 or 20 : 00 h (lights on from 07 : 00 to 21 : 00 h daily). The number of melatonin binding sites in hamster and rat brains was at 20 : 00 h 34--56% higher than at 07 : 00 h, without changing their affinity towards [3H]melatonin (hamster: Kd = 53 nM; rat: Kd = 73--77 nM). These alterations in melatonin receptor density may play a role in daily changes in sensitivity to the exogenous methoxyindole.

The sympathetic superior cervical ganglia as peripheral neuroendocrine centers

The superior cervical ganglia (SCG) provide sympathetic innervation to the pineal gland, cephalic blood vessels, the choroid plexus, the eye, carotid body and the salivary and thyroid glands. Removal of the ganglia brings about several neuroendocrine changes in mammals, including the disruption of water balance in pituitary stalk-sectioned rats, and the alteration of normal photoperiodic control of reproduction in hamsters, ferrets, voles, rams and goats. These effects are commonly attributed to pineal denervation. However pinealectomy does not always mimic ganglionectomy in its neuroendocrine sequelae. This paper discusses several examples illustrating the lack of homology of ganglia and pineal removal, including the prolactin release brought about by gonadal steroids in spayed rats, the changes in drinking behaviour caused by ganglionectomy and the control of goitrogenic response to methylmercaptoimidazole in rats. All these examples indicate that SCG removal, at least as far as for neuroendocrinologists and pineal experimenters are concerned, should not be considered simply as “pineal denervation”. A functionally relevant link between SCG and the hypothalamus may occur in rats inasmuch as ganglionectomy depresses norepinephrine uptake and increases the number and responses afα-adrenoceptors in medial basal hypothalamus. Lastly the SCG are active points of concurrency for hormone signals, as revealed by the metabolic changes induced by steroid and anterior pituitary hormones in these structures even in the absence of intact preganglionic connections, as well as by the existence of putative receptors for some of the hormones, namely, estradiol, testosterone and corticosteroids. The SCG appear to constitute a peripheral neuroendocrine center.

Characterization of Flunitrazepam and Beta-Carboline High Affinity Binding in Bovine Pineal Gland

High affinity binding of 3H-flunitrazepam (FNZP) to crude membrane preparations of bovine pineal membranes was examined by a rapid filtration procedure through Whatman GFB paper. At 0 degrees C binding reached equilibrium in about 20 min. Scatchard analysis of data at equilibrium revealed a single population of binding sites with dissociation constant (Kd) = 3.14 +/- 0.45 nM and binding site concentration (Bmax) = 55.6 +/- 5.6 fmol/mg protein. Kinetic analysis of the association and dissociation curves indicated a kinetic Kd = 1.13 nM, in reasonable agreement to that obtained at equilibrium. When various benzodiazepine (BZP) analogues were tested for their ability to inhibit 3H-FNZP binding, the following Ki (nM) were obtained: clonazepam (0.22), Ro 15-1788 (0.48), FNZP (0.95), Ro 5-4864 (greater than 10,000). When the beta-carboline derivative 3H-ethyl-beta-carboline-3-carboxylate ester (E beta CEE) was used as a radioligand, Kd at equilibrium (0.98 nM), kinetic Kd (1.69 nM) and affinity order for analogues were in close agreement to those found for FNZP binding; however, Bmax was about 60% that observed for 3H-FNZP binding. Addition of GABA or pentobarbital (100 microM) to pineal membranes increased 3H-FNZP binding by 55 and 72%. These results suggest the existence of a mixed population of type 1 and type 2 central BZP receptor subclass in bovine pineal gland.

Circadian rhythm and neural regulation of rat pineal angiotensin converting enzyme

Angiotensin converting enzyme was detectable in rat pineal gland and exhibited a circadian rhythm in activity with maximum at the end of the light phase of daily photoperiod. Superior cervical ganglionectomy (SCGx) or exposure to light for 6 days increased enzyme activity and obliterated morning-evening differences, whereas injection of the beta-agonist isoproterenol depressed the high values observed in SCGx animals. These results indicate that angiotensin converting enzyme in the pineal gland is under negative control by the norepinephrine released from pineal sympathetic nerves.

The impact of home safety on sleep in a Latin American country

OBJECTIVESnWe sought to assess the impact of feelings of safety in ones neighborhood and home on sleep quality and sleep duration.nnnDESIGNnThe design is a cross-sectional survey using face-to-face interviews, as part of the Argentine Social Debt Observatory assessment.nnnSETTINGnThe setting is a nationwide data from Argentina.nnnPARTICIPANTSnThere are 5636 participants aged 18 years and older.nnnINTERVENTION (IF ANY)nN/A.nnnMEASUREMENTSnThe relationships between both subjective sleep quality and self-reported sleep duration, categorized as short (<7 hours), normal (7-8 hours), and long (>8 hours) with safety in ones neighborhood and ones home, were analyzed. Age, sex, obesity, neighborhood socioeconomic status, and education were included as covariates.nnnRESULTSnFeeling unsafe in ones home was strongly associated with poorer sleep quality and with short sleep duration. Feeling unsafe in ones neighborhood was initially associated with reduced sleep quality but was no longer significant after controlling for home safety. In contrast, we found no correlation between safety measures and long sleep. In analyses stratified by sex, feeling unsafe in ones home was associated with poor sleep quality in women but not in men.nnnCONCLUSIONSnOur findings suggest that safety in the home has an important effect on both sleep quality and duration, particularly among women. In contrast, after accounting for safety in the home, neighborhood safety does not impact sleep. Further research is warranted to identify mechanisms underlying the sex differences in susceptibility to poor sleep quality and shorter sleep duration, as well as to assess whether interventions addressing safety in the home can be used to improve sleep and overall health.

Norepinephrine turnover in pineal gland and superior cervical ganglia. Changes after gonadotrophin administration to castrated rats.

The effects of FSH and LH on norepinephrine (NE) turnover in pineal gland and superior cervical ganglia of castrated female rats were examined by measuring the decline of [3H]NE concentration in the organ 30–120 min after a single i.v. injection of the labeled amine. Both FSH and LH treatment significantly decreased [3H]NE turnover in the pineal gland whereas only FSH accelerated it in the ganglia. As compared to controls, the initial uptake of [3H]NE was lower in the pineal gland of FSH- and LH-treated animals, and higher in the superior cervical ganglia of rats injected with FSH. Neither FSH nor LH modified [3H]NE turnover in heart or adrenal gland, nor changed their endogenous catecholamine content. Pineal monoamine oxidase (MAO) activity type B (assaying by usingβ-phenylethylamine as substrate) was decreased by FSH or LH injection. Only FSH modified MAO activity in the ganglia by increasing significantly type A enzyme (assaying by using serotonin as substrate). These results suggest that FSH and LH affect significantly NE metabolism in pineal gland and superior cervical ganglia of spayed rats.

Changes in growthormone and prolactin release after superior cervical ganglionectomy of rats

Superior cervical ganglionectomy (SCG X) decreased significantly serum growth hormone (GH) levels in rats 14-96 h after surgery, during and immediately after anterograde degeneration of regional sympathetic terminals. At later times (up to 28 days after SCG X) an increase in serum GH was observed. SCG X augments prolactin (PRL) release, but only at the earliest time examined (14 h after surgery). Injection of the alpha-adrenoceptor blocker, phenoxybenzamine, but not of the beta-blocker, propranolol, negated the depression in serum GH found in SCG X rats 14 h after surgery, without affecting PRL release.

Effects of castration, estradiol and testosterone on tubulin levels of the medial basal hypothalamus and the adenohypophysis of the rat

Tubulin levels of the medial basal hypothalamus (MBH) were greater in male than in female rats. Orchidectomy brought about a decrease of MBH tubulin concentration, whereas testosterone injection augmented it in the MBH and adenohypophysis. Estradiol administration augmented MBH tubulin and protein concentration.

Pineal--related changes in cyclic AMP levels of rat medial basal hypothalamus.

Pinealectomy (Px) in adult male rats resulted in increased cyclic AMP accumulation by medial basal hypothalamic (MBH) explants 3 and 7 days after surgery. 24 h after superior cervical ganglionectomy (Gx) an augmented MBH cyclic AMP accumulation was observed. The effects of Px and Gx were additive, as revealed in animals subjected to Gx 3 days after Px.

Progesterone-induced decrease of pineal protein synthesis in rats. Possible participation in estrous-related changes of Pineal function

Pineal protein synthesis in female rats, estimated from the incorporation of labeled amino acids into proteinsin vitro, exhibited significant changes as a function of the stage of the estrous cycle. These changes were restricted to the proestrous and estrous days; pineal protein synthesis attained its maximum on the morning of proestrus declining abruptly by 53% during the evening, at the time of the expected gonadotrophin and prolactin release. Pineal serotonin-N-acetyltransferase activity increased by 10 to 15 times during night-time on every day of cycle; no appreciable modification of its daily rhythm was detected along the estrous cycle. Spayed rats treated for 2 days with progesterone showed a dose-dependent decrease of amino acid incorporation into pineal proteins, regardless of whether estradiol was simultaneously administered or not. Pineal protein synthesis in spayed rats administered with estradiol for 2 days and killed at 11 a.m. and 5 p.m. on the third day, did not show differences as a function of time of sacrifice. When progesterone was injected on the morning of the third day a significant decline in protein synthesis was observed at 5 p.m. Only in the latter group serum LH levels showed significantly greater values at 5 p.m. Pineal serotonin content of estradiol-treated rats increased significantly at evening, an effect which was obliterated by the administration of progesterone; progesterone alone did not affect pineal serotonin content. Radioactivity uptake by pineal glands incubated with labeled progesterone did not show changes along the estrous cycle. These data argue in favour of the involvement of progesterone in the changes of pineal protein synthesis observed during the “critical period” for gonadotrophin and prolactin release.