Indexed on: 20 Dec '18Published on: 20 Dec '18Published in: Journal of neurophysiology
Activation of corticotropin-releasing hormone (CRH) type 2 receptors (CRHR2) in the nucleus of the solitary tract (NTS) contributes to the development of hypertension, but the source of CRH inputs to the NTS that increases blood pressure remains unknown. This study tested the hypothesis that activation of CRH-containing projections from the paraventricular nucleus of the hypothalamus (PVN) to the NTS increase blood pressure. We expressed Channelrhodopsin 2 (ChR2), a light sensitive ion channel, into CRH-containing neurons in the PVN. This was achieved by injecting Cre-inducible virus expressing ChR2 into the PVN of CRH-Cre mice. CRH-Cre mice are genetically modified mice expressing Cre recombinase only in neurons producing CRH. We found that optogenetic stimulation of CRH-containing somas in the PVN or CRH-containing fibers in the NTS originating from the PVN significantly increased blood pressure and heart rate. Microinjection of K41498 (CRHR2 antagonist) into the NTS attenuated the pressor and tachycardiac responses induced by optogenetic stimulation of CRH-containing somas in the PVN. In vitro loose-patch recordings revealed that optogenetic stimulation of CRH-containing fibers in the NTS originating from the PVN significantly increased the discharge frequency of NTS neurons. This effect was attenuated by pretreatment of K41498 and was abolished by pretreatment of kynurenic acid (non-selective glutamate receptor antagonist). These results suggest that activation of PVN-NTS CRH-containing projections increases blood pressure and heart rate. The cardiovascular responses may be mediated at least in part by the co-release of CRH and glutamate from NTS CRH-containing axons originating from the PVN.
Indexed on: 18 Dec '20
Published on: 18 Dec '20 in The Journal of neuroscience : the official journal of the Society for Neuroscience