Components of the cannabinoid system in the dorsal periaqueductal gray are related to resting heart rate.
The present study was undertaken to examine whether variations in endocannabinoid signaling in the dorsal periaqueductal gray (dPAG) are associated with baseline autonomic nerve activity, heart rate, and blood pressure. Blood pressure was recorded telemetrically in rats, and heart rate and power spectral analysis of heart rate variability were determined. Natural variations from animal to animal provided a range of baseline values for analysis. Transcript levels of endocannabinoid signaling components in the dPAG were analyzed, and endocannabinoid content and catabolic enzyme activity were measured. Higher baseline heart rate was associated with increased anandamide content and with decreased activity of the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), and it was negatively correlated with transcript levels of both FAAH and monoacylglycerol lipase (MAGL), a catabolic enzyme for 2-arachidonoylglycerol (2-AG). Autonomic tone and heart rate, but not blood pressure, were correlated to levels of FAAH mRNA. In accordance with these data, exogenous anandamide in the dPAG of anesthetized rats increased heart rate. These data indicate that in the dPAG, anandamide, a FAAH-regulated lipid, contributes to regulation of baseline heart rate through influences on autonomic outflow.
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin cdean@mcw.edu.
Caron
C
Dean
Department of Pharmacology, Medical College of Wisconsin, Milwaukee, Wisconsin; and.
Cecilia J
CJ
Hillard
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin.
Jeanne L
JL
Seagard
Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin.
Francis A
FA
Hopp
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin.
Quinn H
QH
Hogan
D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D063388:Endocannabinoids / Q000378:metabolism*; D025461:Feedback, Physiological / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D010487:Periaqueductal Gray / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012146:Rest / Q000502:physiology
D063388:Endocannabinoids
dorsal periaqueductal gray; endocannabinoids; heart rate; rat; sympathetic nerve activity