AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 5 819-R825, Copyright © 1992 by American Physiological Society
Alpha 2-adrenergic regulation of galanin and norepinephrine release from canine pancreas
A. J. Scheurink, T. O. Mundinger, B. E. Dunning, R. C. Veith and G. J. Taborsky Jr
Division of Endocrinology, Metabolism, and Nutrition, Seattle Veterans Affairs Medical Center, Washington.
We found previously that electrical stimulation of the mixed autonomic
pancreatic nerves (MPNS) is anesthesized dogs elicits marked and rapid
increases of pancreatic output of both norepinephrine (NE) and galanin, and
on that basis hypothesized a role for galanin as a sympathetic
cotransmitter in the endocrine pancreas. In the present study, direct
evidence was sought for the co-release of galanin and NE from canine
pancreas by determining whether pancreatic galanin output is subject to
modulation by presynaptic alpha 2-adrenergic mechanisms as has been
established for NE. During MPNS (8 Hz, 1 ms, 10 mA, 10 min) in anesthesized
dogs, both pancreatic NE and galanin outflow were increased with similar
temporal patterns during consecutive stimulations. Blockade of presynaptic
alpha 2-adrenoceptors with yohimbine increased and stimulation of
presynaptic alpha 2-adrenoceptors with clonidine reduced NE and galanin
outflow. Over all experiments, pancreatic spillover of galanin was highly
correlated with that of NE. It is concluded that presynaptic alpha
2-adrenergic mechanisms modulate not only NE but also pancreatic galanin
release, suggesting that galanin is co-released with NE from noradrenergic
nerves in the endocrine pancreas.
