Processing cardiovascular information in the vlPAG during electroacupuncture in rats: roles of endocannabinoids and GABA

Stephanie C. Tjen-A-Looi, Peng Li, and John C. Longhurst Susan Samueli Center for Integrative Medicine, Department of Medicine, School of Medicine, University of California, Irvine, Irvine, California J Appl Physiol 106: 1793–1799, 2009. First published March 26, 2009; doi:10.1152/japplphysiol.00142.2009. The arcuate nucleus (ARC) provides excitatory to the ventrolateral periaqueductal gray (vlPAG) which then inhibits the activity of bulbospinal neurons in the RVLM. Previously this lab showed that electroacupuncture leads to reductions in GABA in the vlPAG. Suggesting the EA promotes increased inhibition on RVLM neurons and therefore decreased sympathetic nervous system activity. For this study they hypothesized that during EA endocannabinoids acting on CB1 receptor presynaptically inhibit GABA release to disinhibit the vlPAG and lead to decrease RVLM neuronal activity and ultimately decreased sympathetic output. So looked at how EA would affect gastric distention responses. When gastric distention occurs it causes a pressor response They found that EA reduced blood pressure responses significantly. They also in fatty acid amide hydrolase inhibitor, which will lead to enhanced endocannabinoids release into the vlPAG. They found that this also attenuated blood pressure responses to gastric distention. Then they gave Gabazine and then the fatty acid hydrolase inhibitor into the vlPAG and found that the gastric distention cause pressor they found similar finding with AM251, a CB1 receptor blocker. Finally they gave both Gabazine and AM251 a CB1 receptor blocker and saw that the gastric diction was still able to cause a pressor response. These findings suggest that EA leads ti attenuated sympathetic output by disinhibition of vlPAG which leads to inhibition of the neuronal activity in the RVLM. -MD