Melatonin Production by the Guinea Pig Pineal Gland in vitro

McCance, I.; Parkington, Helena C.; Coleman, Harold A.

doi:10.1159/000125561

Cited by 4 publications

(5 citation statements)

References 32 publications

(45 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since Tait et al (18) designed a device for in vitro perifusion of rat adrenal glands, the perifusion technique has been applied to other endocrinological studies, among which is pineal research (7)(8)(9)(10)16). Obviously, the device has the advantage of showing the kinetic characteristics of hormone secretion.…”

Section: Discussionmentioning

confidence: 99%

“…An effect of this minimal stimulation, therefore, cannot explain the rapid drop of melatonin in the perifusate of pineal glands obtained during the dark phase. (ii) The absence of melatonin precursors in the peri¬ fusion medium also cannot explain the rapid de¬ crease in melatonin release because melatonin production continues in this medium (8,9,16) as well as in other tryptophan-free media (10) for prolonged time-spans. (iii) An interaction of catecholamines, especially norepinephrine, with pineal melatonin production at the times of activity and/or rest of the animals can be considered as playing a role in the drop observed.…”

Section: Discussionmentioning

confidence: 99%

“…Pineal glands (two per chamber) were perifused with Krebs-Ringer solution for 8 h at a constant flow rate of 0.2 ml/min. After discarding the first 10 min of effluent (equilibration period), the effluent perifusate fractions were collected every 10 min in glass tubes over an 8-h Statistical analysis A single exponential model was used to approximate the initial melatonin release phase and to calculate the halftime of release of melatonin (16). All results obtained were expressed as means ±sem.…”

Section: Rat Synchronizationmentioning

confidence: 99%

See 2 more Smart Citations

Kinetic changes of melatonin release in rat pineal perifusions at different circadian stages. Effects of corticosteroids

Zhao

Touitou

1993

Acta Endocrinologica

View full text Add to dashboard Cite

Zhao Z-Y, Touitou Y. Kinetic changes of melatonin release in rat pineal perifusions at different circadian stages. Effects of corticosteroids.The kinetic characteristics of melatonin release were documented in perifused pineal glands removed from rats sacrificed at six circadian stages (light/dark =12:12): three during the light phase, i.e. 3, 7 and 11 hours after light onset (HALO), and three during the dark phase, i.e. 15,19 and 23 HALO. Whatever the circadian stage, the melatonin release decreased during the first 3\p=n-\4h and then remained fairly constant and roughly similar up to 8 h of perifusion. However, the kinetics of the release in the first 3 h differed in perifusions of pineal glands removed during the light (progressive decline during 3 h) as compared to perifusions of pineal glands removed during the dark (sharp decline during the first hour and then a progressive decline until reaching a constant level after 3 h).As the effects of steroid administration on melatonin secretion are a matter of controversy, we also studied the direct effects and their circadian stage dependence, if any, of corticosterone, deoxycorticosterone and dexamethasone on melatonin secretion by pineal glands removed 7 HALO (about the middle of the light phase) and 19 HALO (about the middle of the dark phase). High concentrations of corticosterone (0.8 \m=x\10\m=-\1 mol/l) and dexamethasone (0.4\m=x\10\m=-\3 mol/l) resulted in a significant (p<0.001) inhibitory effect on melatonin production (about a 50% and a 30% decrease, respectively) whatever the circadian stage, whereas lower concentrations (10\m=-\4\p=n-\10\m=-\5mol/l of both steroids did not affect melatonin production. In addition, neither pharmacological (1.06 \m=x\10\m=-\5 mol/l) nor physiological (for the rat) concentrations (2.1 \m=x\10\m=-\7 mol/l) of deoxycorticosterone had any significant effect on pineal melatonin production. These data clearly show the time dependence of the kinetics of melatonin release and an effect of adrenocortical steroids on pineal melatonin production that may be quite different according to the steroid and dosage.The relationship between the pineal and the adrenal gland is poorly understood and controversial data have been published on the effects of steroid administration on melatonin secretion in vivo. For example, after rat adrenalectomy the pineal melatonin content and the activity of N-acetyltransferase were found to be either depressed (1) or unaltered (2, 3). Likewise, hydroxyindole-O-methyltransferase activity was found to be either increased (4) or unaltered (5). On the other hand, a time-dependent pineal effect upon pituitary-adrenal interaction was reported (6). This investigation in vitro showed a stimulation, no effect or even inhibition of corticosterone production in mouse adrenal gland, depending upon the stage in the circadian cycle when the adrenal glands were obtained. This prompted us to study the effects of two major physiological steroids in the rat, i.e. corticosterone, deoxycorticosterone (DOC) and an anti-infla...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Rat Synchronizationmentioning

confidence: 99%

See 1 more Smart Citation

Kinetic changes of melatonin release in rat pineal perifusions at different circadian stages. Effects of corticosteroids

Zhao

Touitou

1993

Acta Endocrinologica

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

“…Two identical organ baths were used and the samples from each pair were assayed at the same time. Melatonin concentrations were determined by radioimmunoassay (RIA), using the methods described by McCance et al (1990). The least detectable rate of melatonin production was 5 pg/1.5 mL sample, inter-and intra-assay coefficients of variations (CVs) less than 15% at 80 pg/mL.…”

Section: Methodsmentioning

confidence: 99%

How important is stimulation of α‐adrenoceptors for melatonin production in rat pineal glands?

Tobin

McCance

Coleman

et al. 2002

Journal of Pineal Research

View full text Add to dashboard Cite

The objective of this study was to determine the role of alpha-adrenoceptors in melatonin production by rat pineal gland. Pineal glands were isolated from adult male rats and maintained in organ baths. The perfusate was sampled every 5 min, stored, and later assayed for melatonin. Exposure to norepinephrine (10 microM) or the beta-adrenoceptor agonist orciprenaline (2-10 microM) increased the glands' production of melatonin. The time courses of melatonin production in response to these agonists were unaffected by the rats' pretreatment in vivo with the alpha-adrenoceptor antagonist prazosin (2 mg/kg i.p., three times). Rats that had had their superior cervical ganglia removed were primed with either orciprenaline (2 mg/kg i.p) or both orciprenaline and phenylephrine (1 mg/kg i.p) 1 hr before decapitation. Exposure of the pineal glands from these rats to orciprenaline evoked melatonin release that was similar in each group. These results lend weight to the suggestion that the marked potentiation by alpha-adrenoceptor agonists of the stimulation of cAMP and N-acetyltransferase (NAT) by beta-adrenoceptor agonists, demonstrated most readily in cultured glands or dispersed rat pinealocytes, does not carry over into significant augmentation of melatonin production in intact pineal glands.

show abstract

Development of Oxytocinergic Neurons in Monolayer Cultures Derived from Embryonic, Fetal and Postnatal Rat Hypothalami

Madarász

Környei

Poulain

et al. 1992

J Neuroendocrinology

View full text Add to dashboard Cite

Monolayer cultures from hypothalami of embryonic, fetal and postnatal rats were established to study the development of oxytocin-secreting neurons in vitro. Particular culture conditions, known to enhance the survival and growth of different types of neural cells in vitro, were used to investigate the conditions necessary for the appearance and survival of these peptide-producing cells in culture. They included increasing the concentration of potassium in the culture milieu and/or the addition of triiodothyronine (T(3) ). The use of immunocytochemical procedures with a monoclonal antibody that recognizes oxytocin-associated neurophysin (NP-OT) and polyclonal antibodies specific for oxytocin permitted us to identify the neurons. In cultures derived from embryonic (E16-E17) hypothalami, no NP-OT- or oxytocin-positive neurons were detected and their appearance could not be provoked by increasing extracellular potassium concentration or by administration of T(3) . On the other hand, in cultures obtained from fetal (E18-E19) rat hypothalami, a few neurons showed immunoreactivity for NP-OT (but not for oxytocin); the immunoreactivity was localized essentially in somata and proximal portions of neurites. When 10(8) M T(3) was included in the culture medium, there were cells showing immunoreactivity not only for NP-OT, but also for oxytocin, visible in somata and in dendritic- and axonal-like processes. In comparison, T(3) did not influence the total number of neurons developing in these cultures. Lastly, in cultures derived from young postnatal (PO-P2) rat hypothalami, NP-OT- and oxytocin-immunopositive neurons were found regularly; their appearance did not require any special pretreatment of the cultures. In all cultures, high extracellular potassium concentration (25 mM) resulted in a general improvement in the survival of neurons but did not induce the appearance of more oxytocin-immunoreactive cells. Our observations support in vivo results showing that although presumptive oxytocin-producing cells appear early in the development of the hypothalamus, their maturation, and in particular, their ability to produce oxytocin, occurs late at the time of birth. A factor that selectively enhances their differentiation, is the thyroid hormone, T(3) .

show abstract

Melatonin Production by the Guinea Pig Pineal Gland in vitro

Cited by 4 publications

References 32 publications

Kinetic changes of melatonin release in rat pineal perifusions at different circadian stages. Effects of corticosteroids

Kinetic changes of melatonin release in rat pineal perifusions at different circadian stages. Effects of corticosteroids

How important is stimulation of α‐adrenoceptors for melatonin production in rat pineal glands?

Development of Oxytocinergic Neurons in Monolayer Cultures Derived from Embryonic, Fetal and Postnatal Rat Hypothalami

Contact Info

Product

Resources

About