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Paraventricular Stimulation with Glutamate Elicits Bradycardia and Pituitary ResponsesThe excitatory neurotransmitter, L-glutamate (0.5 M, pH 7.4), or the organic acid, acetate (0.5 M, pH 7.4), was microinjected (50 nl over 2 min) directly into the paraventricular nuclei (PVN) of pentobarbital sodium-anesthetized rats while arterial blood pressure and heart rate and plasma adrenocorticotropic hormone (ACTH), vasopressin, and oxytocin were measured. Activation of PVN neurons with L-glutamate led to increases in plasma ACTH, vasopressin, and oxytocin and a profound bradycardia (-80 beats/min) with little change in arterial blood pressure. Microinjection of acetate had no effect on the above variables. The decrease in heart rate was shown to be dependent on the concentration of glutamate injected and the volume of injectate. The bradycardia was mediated through the autonomic nervous system because ganglionic blockade (pentolinium tartrate) eliminated the response; atropine and propranolol severely attenuated the bradycardia. The bradycardia was greatest when L-glutamate was microinjected into the caudal PVN. Injections into the rostral PVN or into nuclei surrounding the PVN led to small or nonsignificant decreases in heart rate. Focal electric stimulation (2-50 pA) of the PVN also led to decreases in heart rate and arterial blood pressure. These data suggest that activation of PVN neurons leads to the release of ACTH, vasopressin, and oxytocin from the pituitary and a bradycardia that is mediated by the autonomic nervous system.
Document ID
Document Type
Reprint (Version printed in journal)
Darlington, Daniel N.
(NASA Ames Research Center Moffett Field, CA United States)
Miyamoto, Michael
(NASA Ames Research Center Moffett Field, CA United States)
Keil, Lanny C.
(NASA Ames Research Center Moffett Field, CA United States)
Dallman, Mary F.
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1989
Publication Information
ISSN: 0363-6119
Subject Category
Life Sciences (General)
Report/Patent Number
NAS 1.26:2048811
Funding Number(s)
Distribution Limits
Public Use Permitted.
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