Possible Involvement of Nitric Oxide in Acetylcholine-Induced Increase of Intracellular Ca²⁺ Concentration and Catecholamine Release in Bovine Adrenal Chromaffin Cells

Abstract

The role of nitric oxide (NO) in neurotransmitter release was studied using bovine adrenal medullary chromaffin cells. L-Arginine and sodium nitroprusside (SNP) slightly increased the intracellular free calcium concentration ([Ca²⁺]_i), and the effects of the agents were dependent on the presence of the extracellular Ca²⁺ ([Ca²⁺]_o), but were not blocked by verapamil (30 μM) or diltiazem (30 μM). SNP enhanced the acetylcholine (ACh)-induced rise in [Ca²⁺]_i in the presence but not in the absence of [Ca²⁺]_o. The effects of L-arginine but not those of SNP were inhibited by N^ω-nitro-L-arginine (L-NNA). L-NNA significantly reduced the ACh-induced rise in [Ca²⁺]_i and catecholamine (CA) release, and the reduction was restored by L-arginine but not by D-arginine. These results suggest a possible involvement of NO in ACh-induced [Ca²⁺]_i rise and CA release in bovine adrenal chromaffin cells.