Demonstration of action-potential-producing cells in the rat pineal gland in vitro and their regulation by norepinephrine and nitric oxide.
There is evidence that sympathetically innervated mammalian pineal glands contain cells that exhibit action potentials. It is unknown whether ex vivo pineal glands deprived of their nervous input are still capable of firing. In the present study, multiple-unit recordings from rat pineals revealed spontaneously active cell clusters with a mean firing frequency of 1.5 +/- 0.3 Hz which could be abolished by tedrodotoxin. Regularly firing clusters showed no inherent periodicity in the minute range, whereas rhythmical clusters with periodically repeated bursts had period lengths of 12.6 min (day) and 9.5 min (night). Superfusion of norepinephrine reduced the firing frequency of both cluster types, or had no effect, and the rhythmical clusters became regular. The effects of norepinephrine appear to be mediated via beta-adrenoceptors because isoproterenol, a beta-agonist, had the same effect as norepinephrine and as the alpha-agonist phenylephrine was without effect. Evidence was obtained that the inhibitory effect of norepinephrine may be mediated by nitric oxide, which appears to affect the electrical discharge of the cells directly or indirectly through cGMP. It is discussed whether the spontaneously active pineal cells represent an intrapineal oscillator or are driven by an intrinsic oscillator which has yet to be defined.
Schenda
J
J
Department of Anatomy, Johannes Gutenberg University, Mainz, Germany. schenda@mzdmza.zdv.uni-mainz.de
Vollrath
L
L
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D004594:Electrophysiology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010870:Pineal Gland / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology*
C110881:S-nitro-N-acetylpenicillamine; D013439:Sulfhydryl Reagents; D013566:Sympathomimetics; D009599:Nitroprusside; D019335:Nitroarginine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D009569:Nitric Oxide; D010396:Penicillamine; D006152:Cyclic GMP; D007545:Isoproterenol; D009638:Norepinephrine