Abstract:In this study the subunits of the dihydropyridine-sensitive L-type Ca2~channels (L-channels) expressed in rat pinealocytes were characterized using reverse transcription (RT)-PCR analysis, and the modulation of these channels by adrenergic agonists and by pituitary adenylate cyclase-activating polypeptide (PA-CAP) was studied using the patch-clamp technique. RT-PCR analysis showed that rat pinealocytes expressed a2b, /32, and /34 Ca2-channel subunit mRNAs. Other a 1 subunit transcripts were either not expressed or present at very low levels, indicating that the pinealocytes express predominantly aID L-channels. Electrophysiologcal studies confirmed that the pineal expressed a single population of L-channels. The L-channel currents were inhibited by two agonists that elevate cyclic AMP: the /3-adrenergic agonist isoproterenol and PACAP. Similar inhibition was observed with a cyclic AMP analogue, 8-bromo-cyclic AMP. The presence of a cyclic AMP antagonist, Rp -adenosine 3',5 '-cyclic monophosphorothioate, blocked the inhibition by isoproterenol and PACAP. Norepinephrine, a mixed a-and f3-adrenergic agonist, also inhibited the L-channel currents, but the inhibition was smaller. The smaller inhibition by norepinephrine was secondary to the simultaneous activation of a-and /3-adrenergic receptors. These results indicatethat (a) pinealocytes express predominantly a~L-channels, and (b) the /3-adrenergic agonist isoproterenol and PACAP inhibit the L-channel currents through elevation of cyclic AMP. However, an a-adrenergic-mediated mechanism also appears to be involved in the effect of norepinephrine on the L-channel currents. Key Words: Ca 2~channel-Cyclic AMP-Norepinephrine-PACAP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.