AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 3 788-R797, Copyright © 1990 by American Physiological Society
Metabolic activation of efferent pathways from the rat area postrema
P. M. Gross, D. S. Wainman, S. W. Shaver, K. M. Wall and A. V. Ferguson
Department of Surgery, Queen's University, Kingston, Ontario, Canada.
We used the quantitative [14C]deoxyglucose method and autoradiography to
evaluate metabolic activity in 47 individual cerebral structures or
subregions that are part of neural pathways emanating from the brain stem
circumventricular organ, area postrema. Electrical stimulation of the
dorsocentral area postrema in halothane-ventilated rats produced
hypotension and increased glucose metabolism by several structures within
the ascending trajectories of efferent neural projections from the nucleus.
Structures in the caudal medulla oblongata, including three subnuclei of
the nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve,
and nucleus ambiguus-A1 noradrenergic region, had increases of metabolism
during stimulation of 32-62%. Pontine activation occurred specifically in
the locus coeruleus and lateral parabrachial nuclei (increases of 24-36%).
Magnocellular and parvocellular subdivisions of the hypothalamic
paraventricular nucleus, supraoptic and suprachiasmatic nuclei, and median
eminence showed increases in metabolism of 22-34%. An 89% elevation of
glucose metabolism by the pituitary neural lobe resulted. The findings are
evidence for functional activation of specific structures within ascending
neural pathways from area postrema to forebrain mechanisms regulating blood
pressure and fluid balance.
