AJP - Heart and Circulatory Physiology, Vol 273, Issue 2 540-H545, Copyright © 1997 by American Physiological Society
Cardiovascular responses to glutamate stimulation of diagonal band of Broca
G. J. Kirouac and J. Ciriello
Department of Physiology, University of Western Ontario, London, Canada.
Experiments were done in alpha-chloralose-anesthetized, paralyzed, and
artificially ventilated rats to investigate the effect of L-glutamate
stimulation of the diagonal band of Broca (DBB) on arterial pressure (AP)
and heart rate (HR). Stimulation of the horizontal limb of the DBB (hDB)
elicited decreases in both mean AP (MAP; -32.3 +/- 2.5 mmHg; n = 37) and HR
(-32.5 +/- 3.8 beats/min; n = 33) at 84% of the sites stimulated.
Stimulation of the vertical limb of the DBB (vDB) elicited significantly
smaller decreases in MAP (-9.7 +/- 1.0 mmHg; n = 19) and HR (-13.5 +/- 1.8
beats/min; n = 7) at approximately 13% of the sites stimulated. Intravenous
administration of the muscarinic receptor blocker atropine methylbromide
had no effect on the magnitude of the MAP and HR responses to stimulation
of the hDB. In contrast, administration of the nicotinic receptor blocker
hexamethonium bromide abolished both the depressor and the bradycardic
responses elicited by stimulation of the hDB. These data indicate that the
hDB contains neurons that exert cardiovascular depressor effects and that
these circulatory effects are mediated by the inhibition of sympathetic
vasoconstrictor fibers to the vasculature, and cardioacceleratory fibers to
the heart.
