AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 5 641-R645, Copyright © 1983 by American Physiological Society
Dual mechanism for catecholamine secretion in the dogfish shark Squalus acanthias
D. F. Opdyke, J. Bullock, N. E. Keller and K. Holmes
Both 1,1-dimethyl-4-phenylpiperazinium iodide, a ganglionic stimulating
drug (DMPP), and potassium ion (K+) cause a pressor response when injected
into Squalus acanthias, an elasmobranch. The pressor responses are due to
increased secretion of epinephrine and norepinephrine. The pressor response
to DMPP can be blocked by prior infusion of hexamethonium, a ganglionic
blocking drug. However, ganglionic blockade does not inhibit the pressor
response to K+. Plasma catecholamine concentrations do not increase
significantly in response to challenge with DMPP after hexamethonium
infusion, but exceedingly high levels of plasma catecholamines quickly
appear after K+ injection following hexamethonium infusion. It is concluded
that there are at least two mechanisms controlling catecholamine secretion
in the dogfish, one of which involves the ganglion cells that are
intimately associated with chromaffin cells in the chromophil bodies that
are so characteristic of this species and elasmobranchs in general.
