Publication: Nitric oxide synthase in the pineal gland
Authors
Lopez-Figueroa, M.O. ; Moller, M.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
The recent discovery of nitric oxide (NO) as
a biological messenger molecule with unique
characteristics has opened a new field in pineal research.
This free radical gas is synthesized by the enzyme nitric
oxide synthase (NOS) from L-arginine. The activation of
adrenoreceptors in the membrane of the pinealocytes
mediates the increase in NO through a mechanism that
involves G proteins. In the pinealocyte, NO stimulates
guanylyl cyclase resulting in an increased intracellular
content of cGMP. The role of cGMP in pineal
metabolism, however, is still enigmatic
Using enzyme histochemistry and immunohistochemistry,
the presence of NOS has been confirmed in
the pineal gland of some species. In the rat and
especially in the sheep, NOS is located in nerve fibres
innervating the gland. These nerve fibres also contain
the neuropeptides vasoactive intestinal peptide (VIP) and
peptide histidine isoleucine (PHI), and are probably of
parasympathetic origin. In cell cultures and tissue
sections NOS immunoreactivity has been shown to be
present in pinealocytes of the rat and bovine but not in
the sheep. Finally, NOS is also present in the endothelial
cells of the blood vessels of the pineal gland.
Accordingly, in the mammalian pineal gland, NO is
synthesized in both presynaptic nerve fibers and
pinealocytes, as well as in blood vessels. However, the
anatomical location of NO synthesis varies considerably
among species. NO released in the pineal gland, might
influence both the pineal metabolism and the blood flow of the gland.
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