Changes with darkness in regional brain 5-hydroxytryptamine and 5-hydroxyindole acetic acid: Local differences with pinealectomy, sham surgery, and melatonin

Abstract

Brain regional 5-HT (5-hydroxytryptamine) and 5-HIAA (5-hydroxyindole-3-acetic acid) concentrations in male LE rats at three times were measured by a fluorescence method, to evaluate effects of intracranial surgery and administration of melatonin on the changes in these compounds during the first part of the dark phase of the daily cycle in a fixed 12:12 L:D photoperiod. Early surgical pinealectomy or a similar but sham intracranial surgery, led to delay in darkness-associated fall in frontal cortical and striatal 5-HT. A single melatonin injection two hours before darkness, reversed this effect in frontal cortex but not striatum. Melatonin's specification of action in this experiment is interpreted as residing in specific timing of release and/or administration, rather than in either a fixed or general basis neurochemically.

Melatonin increases cell proliferation in the dentate gyrus of maternally separated rats

“…Melatonin, the major secretory product of the pineal gland, has been known to interact with neuroendocrine axis [2] and circadian rhythms [1]. Recently, several studies demonstrated that melatonin acts as an antioxidant and a potent free radical scavenger [7, 9, 17, 18], and provides protective effects on neuronal cells [9, 19].…”

“…Melatonin is a chemical mediator produced by the pineal gland and in other tissues. The classical functions of melatonin are associated with the control of the circadian rhythms [1] and the regulation of hypothalamic–pituitary–gonadal axis [2], while other effects of the indole have also been reported [3–6]. Recently, melatonin has been shown to have antioxidant capacity, acting both as a free radical scavenger [7] and a protective agent in neuronal cells [8, 9].…”

Effects of single doses and daily melatonin treatments on serotonin metabolism in rat brain regions

“…Evidence has accumulated to indicate that melatonin acts on brain to regulate serotoninergic neuro- transmission. For example, alterations in brain serotonin levels have been observed in rats and hamsters after melatonin administration [Anton-Tay et al, 1968;Quay, 1989;Alexiuk and Vriend, 19911. However, these studies have not always yielded similar results.…”

“…Moreover, several reports have described changes in brain serotonin (5-HT) content after alterations of the pineal function or after melatonin administration [Anton-Tay et a]. , 1968; Aldegunde et al, 1985;Vriend, 1989;Quay, 1989;Alexiuk and Vriend, 1991;Steger and Bartke, 19911. In previous studies, we have observed that pinealectomy decreased 5-HT synthesis in some hypothalamic regions and in the amygdala [Miguez et a]., 1991a,b]. In these areas, pinealectomized rats also showed decreased levels of the amine or its acid metabolite, 5-hydroxyindole-3acetic acid (5-HIAA).…”

Melatonin Ameliorates Injury and Specific Responses of Ischemic Striatal Neurons in Rats

“…Melatonin, a bioactive compound secreted primarily by the pineal gland in mammals, possesses a variety of physiological functions including regulating circadian and seasonal rhythms (Quay 1989), removing free radicals, and preventing oxidation of biomolecules (Maldonado et al 2007;Tan et al 2007). Earlier research has revealed that a reduction in melatonin is related to various degenerative diseases such as Alzheimer's disease, HD, and Parkinsonism, and thus this compound has been tested for treating various neurodegenerative disorders (Reiter et al 1999;Srinivasan et al 2005).…”