Abstract
The effects of several representative calcium channel antagonists on depolarization-evoked release of [ 3H]-norepinephrine were investigated in isolated, superfused rabbit iris-ciliary bodies. Potassium (50 mM)-evoked neurosecretion was blocked by 5 mM CoCl 2 and partially inhibited by 10 −6 M nitrendipine or verapamil. Electrically-evoked neurosecretion was similarly blocked by CoCl 2, but was unaffected by nitrendipine or verapamil. It is concluded from these results that sympathetic terminals in the rabbit iris-ciliary body contain dihydropyridine- and verapamil-sensitive calcium channels which contribute, under conditions of prolonged depolarization, to neurotransmitter release.
Published Version
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