Melatonin binding sites in the central nervous system.
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Biomedical subjects
B Stankov
Publications and source records attributed to B Stankov.
Influence of acute stress on the pineal activity during day- and nighttime.
Ovariectomized, steroid implanted female ewes were used as a model for studying the effect of acute isolation and confinement stress on the pineal activity during day and nighttime under artificial luteal phase conditions. Male and female intact buffaloes were employed as well, with the aim to establish the influence of another perturbation (venous catheter insertion) on the melatonin levels during daytime. Stress appeared to influence pineal melatonin secretion in controversial manner, namely, decreasing further the low indole levels during the day, while elevating the peripheral concentrations at night, though the initial response to stress during daytime was a transient elevation in melatonin levels. There are no indications that the adrenals are directly involved in the changes observed. Possibilities for different mechanisms of melatonin secretion and release in different species are considered.
Animals↗
High affinity melatonin receptors in the vertebrate brain: implications for the control of the endogenous oscillatory systems.
Currently, the melatonin receptor is depicted as a membrane-associated protein, linked to a guanine nucleotide-binding protein (G-protein), and thus the melatonin receptor represents a member of a receptor superfamily, acting through G-proteins in the first step of their signal-transduction pathways. Although on a number of occasions specific binding of radioactive melatonin has been demonstrated in a wide variety of tissues and organs, to date, high affinity G-protein-regulated melatonin binding sites, suggestive for a functional melatonin receptor, have been convincingly confirmed in the brain only. There is a significant species variation in the distribution of the melatonin receptor in the vertebrate brain. The limited number of studies prevents any definitive conclusion in terms of phylogeny, though generally speaking, the lower vertebrates' brains tend to express melatonin receptors with wider distribution. Two sites have been consistently found to express high density of melatonin receptors: the pars tuberalis of the adenohypophysis and the hypothalamic suprachiasmatic nuclei (SCN). It must be pointed out, however, that there are some exceptions. Binding in the human pars tuberalis has not been reported, and apparently, the sheep and the mustelids' suprachiasmatic nuclei do not express detectable binding. The function of melatonin in pars tuberalis is unclear, and the control of the synthesis (and release) of paracrine factors that act at site(s) distant from the melatonin target cells, have been suggested.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗