Immunocytochemical and circadian biochemical analysis of neuroactive amino acids in the pineal gland of the rat: effect of superior cervical ganglionectomy

Abstract

Semiquantitative immunocytochemistry by immuno-gold techniques revealed differences in the spatial distribution of glutamate, glutamine, and taurine within the pineal gland, with greatest labeling over pinealocytes, glia, and endothelia, respectively. At the subcellular level, glutamate labeling tended to be highest over pinealocyte synaptic ribbons and mitochondria, and lowest over lipid inclusions. Pineal levels of glutamate, glutamine and taurine, as measured by high performance liquid chromatography, did not vary over a light: dark cycle. Superior cervical sympathetic denervation, which abolishes pineal melatonin synthesis, resulted in a nearly 50% reduction in pineal glutamate levels, but had no effect on levels of glutamine and taurine. Other amino acids (alanine, arginine, aspartate, serine) were reduced by 23%-33% following sympathectomy. These data suggest an important role for glutamate in pinealocyte function(s) possibly related to the noradrenergic innervation of the gland.

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…display additional autocrine/paracrine effects. Pineal cells also contain GABA (15% of bovine pineal cells: Rosenstein et al, 1989b), Glu (McNulty et al, 1992), aspartate (Imai et al, 1995), and taurine (LaBella et al, 1968), which are able to alter the metabolic activity of the pineal gland (see Section VI.B.). Intrapineal neurons immunopositive for acetylcholinesterase have been identified in the pineal gland of several mammalian species (Romijn, 1975;.…”

Microvesicles isolated from bovine pineal gland specifically accumulate l‐glutamate

“…Pinealocytes are known to contain relatively high concentration of glutamate [9] and a large number of synaptic-like microvesicles (MVs) [10]. Recent evidence indicated that MVs *Corresponding author.…”

Immunocytochemical Localization of Taurine in the Pineal Organ and Retina of an Anadromous Fish, Plecoglossus altivelis.

“…This strong immunoreactivity has previously been demonstrated in the so-called dark pinealocytes of the pigeon (UECK et al, 1995). In contrast, a uniform distribution of taurine within pinealocytes, glia, and sympathetic fibers has been reported in the pineal gland of the rat (MCNULTY et al, 1992).…”

“…High levels of taurine immunostaining were found in the outer and inner segments and synaptic terminals of some photoreceptor cells; lower levels of immunostaining were reported in the apical processes of pigment epithelium and distal parts of glial cells (LAKE and VERDONE-SMITH, 1989;Pow, 1994). The taurine localization, however, is scarcely known in the photoneuroendocrine pineal organ, except in the case of the pigeon (DECK et al, 1995) and rat (MCNULTY et al, 1992).…”

“…In the pineal organ of the rat, in contrast, taurine content was found higher at mid-day than during night (NIR et al, 1973;MCNULTY et al, 1992) and inhibition of the release and/or synthesis of melatonin has been proposed as a possible role of taurine (BASKIN and DAGIRMANJIAN, 1973).…”