Pinealocyte

About: Pinealocyte is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 55609 citations.

cGMP inhibits L-type Ca2+ channel currents through protein phosphorylation in rat pinealocytes.

Abstract: In this study, the effect of cGMP on the dihydropyridine-sensitive (L- type) Ca2+ current was investigated using the whole cell version of the patch-clamp technique in rat pinealocytes Dibutyryl-cGMP (1 x 10(-4) M) induced a pronounced inhibition of the L-type Ca2+ channel current The dibutyryl-cGMP effect was concentration dependent Elevation of cGMP by nitroprusside had a similar inhibitory action on the L-type Ca2+ channel current Norepinephrine, which increased cGMP in rat pinealocytes, also inhibited this current The action of cGMP was independent of cAMP elevation since the cAMP antagonist, Rp-cAMPs, had no effect on the inhibitory action of dibutyryl-cGMP The involvement of cyclic GMP-dependent protein kinase was suggested by the blocking action of two protein kinase inhibitors, (1-(5-isoquinolinesulfonyl)-2- methylpiperazine (H7) and N-(2-guanidinoethyl)-5- isoquinolinesulfonamide (HA1004), on the dibutyryl-cGMP effect on the L- type Ca2+ channel current Taken together, these results suggest that (1) cGMP modulates L-type Ca2+ channel currents in rat pinealocytes, causing inhibition of this current; (2) the action of cGMP appears to be independent of cAMP elevation; and (3) phosphorylation by cGMP- dependent protein kinase may be involved

α1-Adrenergic Potentiation of Vasoactive Intestinal Peptide Stimulation of Rat Pinealocyte Adenosine 3′,5′-Monophosphate and Guanosine 3′,5′- Monophosphate: Evidence for a Role of Calcium and Protein Kinase-C

Abstract: alpha 1-Adrenergic agonists have recently been found to potentiate vasoactive intestinal peptide (VIP) stimulation of rat pinealocyte cAMP and cGMP. alpha 1-Adrenergic agonists also elevate pineal intracellular Ca2+ [( Ca2+]i) and activate protein kinase-C. In the present study, the possible involvement of Ca2+ and protein kinase-C in the alpha 1-adrenergic potentiation of VIP-stimulated cAMP and cGMP accumulation was examined with agents that alter [Ca2+]i or activate protein kinase-C. It was found that treatment with a Ca2+ chelator or with inorganic Ca2+ channel blockers inhibited alpha 1-adrenergic potentiation of VIP-stimulated cAMP and cGMP responses. Increasing [Ca2+]i by treatment with A23187, ouabain, or K+ potentiated VIP stimulation of cAMP and cGMP response. These observations indicate that Ca2+ mediates the alpha 1-adrenergic potentiation of VIP-stimulated cAMP and cGMP accumulation, as is true for the alpha 1-adrenergic potentiation of beta-adrenergic stimulated cAMP and cGMP accumulation. Activators of protein kinase-C mimicked the large effect alpha 1-adrenergic agonists have on cAMP accumulation in VIP-treated pinealocytes and had a small effect on cGMP accumulation in VIP-treated cells. These effects were not blocked by the Ca2+ chelator EGTA. However, the effects of a protein kinase-C activator on the cGMP response in VIP-stimulated cells were amplified by K+ (15 mM) or ouabain (1 microM), presumably through an action causing an increase in [Ca2+]i. These results suggest protein kinase-C is involved in the alpha 1-adrenergic potentiation of VIP-stimulated cAMP accumulation, as is the case for the alpha 1-adrenergic potentiation of beta-adrenergic stimulated cAMP. Protein kinase-C is also involved in cGMP accumulation, provided that there is a modest increase in [Ca2+]i.

Input and output signals in a model neural system: the regulation of melatonin production in the pineal gland.

Abstract: The production of melatonin has been studied using organ cultures of pineal glands incubated with methionine-methyl-3H. Melatonin-O-methyl-3H was extracted from cultured pineal glands and incubation media, and the activity of N-acetyltransferase was measured. This is the first of two enzymes necessary for the conversion of serotonin to melatonin in the pineal. The treatment of pineal glands with norepinephrine or dibutyryl cyclic AMP increased the release of melatonin-O-methyl-3H into the incubation media and the concentration of melatonin-O-methyl-3H in the glands. These treatments also resulted in the stimulation of N-acetyltransferase, as compared to untreated glands. The transduction of neural information to biochemical, signals which regulate the melatonin pathway appears to involve the release of norepinephrine, which stimulates N-acetyltransferase activity through an adenyl cyclase-cyclic AMP mechanism, as evidenced by these and other studies discussed. In the present study the effects of harmine were studied. This hallucinogen is known to inhibit monoamine oxidase and stimulate melatonin production. Harmine was observed to stimulate N-acetyltransferase. This observation raises the possibility that an important action of this psychotropic drug may be on mechanisms which convert neural activity into biochemical events.