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First published online June 6, 2005
Journal of Experimental Biology 208, 2421-2431 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01636

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Nitric oxide and the control of catecholamine secretion in rainbow trout Oncorhynchus mykiss

B. McNeill and S. F. Perry^*

Department of Biology, University of Ottawa, 10 Marie Curie, Ottawa, ON, Canada K1N 6N5

^* Author for correspondence (e-mail: sfperry{at}science.uottawa.ca)

Accepted 11 April 2005

An in situ saline-perfused posterior cardinal vein preparation was used to assess the role of nitric oxide (NO) in the regulation of basal and stimulus-evoked catecholamine secretion from rainbow trout Oncorhynchus mykiss chromaffin cells. Addition of the NO donor, sodium nitroprusside (SNP) to the inflowing perfusate abolished catecholamine secretion during electrical field stimulation, thereby establishing the potential for NO to act as a potent inhibitor of catecholamine release. A possible role for endogenously produced NO was established by demonstrating that stimulus-evoked (depolarizing levels of KCl or electrical field stimulation) catecholamine secretion was markedly stimulated in the presence of the nitric oxide synthase (NOS) inhibitors L-NAME and 7-NI. Although in vitro experiments demonstrated that catecholamine degradation was enhanced by NO in a dose-dependent manner, the dominant factor contributing to the reduction in catecholamine appearance in the perfusate was specific inhibition of catecholamine secretion. Subsequent experiments were performed to identify the NOS isoform(s) contributing to the inhibition of stimulus-evoked catecholamine secretion. Inducible NOS (iNOS; an enzyme that can be activated in the absence of Ca²⁺), although present in the vicinity of the chromaffin cells (based on mRNA measurements), does not appear to play a role because stimulus-evoked NO production was eliminated during perfusion with Ca²⁺-free saline. The potential involvement of endothelial NOS (eNOS) was revealed by showing that hypoxic perfusate evoked NO production and corresponded with an inhibition of stimulus-evoked catecholamine secretion; chemical removal of the endothelium (using saponin) prevented the production of NO during hypoxia. However, because removal of the endothelium did not affect NO production during electrical field stimulation, it would appear that the neuronal form of NOS (nNOS) is the key isoform modulating catecholamine secretion from trout chromaffin cells.

Key words: adrenaline, noradrenaline, catecholamine, nitric oxide synthase, stress, chromaffin cell, rainbow trout, Oncorhynchus mykiss

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This article has been cited by other articles:

				S. F. Perry, B. McNeill, E. Elia, A. Nagpal, and B. Vulesevic Hydrogen sulfide stimulates catecholamine secretion in rainbow trout (Oncorhynchus mykiss) Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2009; 296(1): R133 - R140. [Abstract] [Full Text] [PDF]

				B. McNeill and S. F. Perry The interactive effects of hypoxia and nitric oxide on catecholamine secretion in rainbow trout (Oncorhynchus mykiss) J. Exp. Biol., November 1, 2006; 209(21): 4214 - 4223. [Abstract] [Full Text] [PDF]