Effects of calcium channel antagonists on the depolarization-evoked release of norepinephrine in the rabbit iris-ciliary body |
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| Authors: | J E Jumblatt |
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| Affiliation: | Department of Ophthalmology, University of Louisville School of Medicine, KY 40202. |
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| 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 CoCl2 and partially inhibited by 10(-6) M nitrendipine or verapamil. Electrically-evoked neurosecretion was similarly blocked by CoCl2, 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. |
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