MODULATION OF GANGLION-CELL ACTIVITY IN THE PINEAL-GLAND OF THE RAINBOW-TROUT - EFFECTS OF CHOLINERGIC, CATECHOLAMINERGIC, AND GABAERGIC RECEPTOR AGONISTS

Citation
R. Brandstatter et A. Hermann, MODULATION OF GANGLION-CELL ACTIVITY IN THE PINEAL-GLAND OF THE RAINBOW-TROUT - EFFECTS OF CHOLINERGIC, CATECHOLAMINERGIC, AND GABAERGIC RECEPTOR AGONISTS, Journal of pineal research, 21(2), 1996, pp. 59-72
Citations number
53
Categorie Soggetti
Neurosciences,"Endocrynology & Metabolism","Anatomy & Morphology
Journal title
ISSN journal
07423098
Volume
21
Issue
2
Year of publication
1996
Pages
59 - 72
Database
ISI
SICI code
0742-3098(1996)21:2<59:MOGAIT>2.0.ZU;2-E
Abstract
Second order neurons within intact isolated pineal glands of the rainb ow trout were explored by extracellular recordings to investigate modu latory effects of putative intrapineal neurotransmitters. Acetylcholin e, dopamine, and norepinephrine were found to increase ganglion cell a ctivity in a majority of cells tested. The excitatory effects of acety lcholine, dopamine, and norepinephrine were mimicked by muscarinic, do pamine D2, and beta-adrenergic receptor agonists and significantly inc reased with the applied light intensity, resulting in an attenuation o f the ganglion cell response to light. GABA decreased discharge activi ty in most cells tested. This effect, which could be mimicked with the GABAA receptor agonist piperidine, was independent from the adaptive status. Acetylcholine and GABA were still active if applied during syn aptic blockade with low Ca high Mg++-perfusion medium, whereas dopamin e and norepinephrine exhibited no effects if applied during synaptic b lockade, suggesting a differential cellular distribution of neurotrans mitter receptors in the trout pineal gland. These data demonstrate tha t ganglion cell activity in the trout pineal gland is under the influe nce of several neurotransmitters, including acetylcholine, dopamine, n orepinephrine, and GABA, which is in contrast to the originally propos ed simple bineuronal transduction pathway from photoreceptors onto gan glion cells. Since the above-mentioned neurotransmitters are believed to be released from pineal interneurons, we may conclude that ganglion cell activity in the teleost pineal gland is, similarly to the retina , the product of photoreceptor signals and a modulatory active interne uronal system.