Endocannabinoid effects on neuronal function in the NTS of hypertensive rats (1130.3)

Abstract

Previously, we showed that endocannabinoid activation of cannabinoid 1 receptors (CB1Rs) in the nucleus tractus solitarius (NTS) activates barosensitive neurons and prolongs baroreflex inhibition of renal sympathetic nerve activity in normotensive Sprague Dawley (SD) rats, but reflex responses were attenuated in spontaneously hypertensive rats (SHR). This study examined the effect of CB1Rs on NTS barosensitive neurons in SHRs to determine if the lack of reflex responses is associated with diminished effects on neuronal firing. NTS neuronal activity was recorded in the working heart brainstem preparation in SHR or SD rats, with increases in perfusion pressure used to identify barosensitive firing. To examine the effects of CB1Rs on neuronal discharge, picoejections of the CB1R agonist anandamide (AEA), antagonist SR141716, or blocker of AEA catabolism, AM404, were made through a multibarrel pipette array which contained the carbon fiber recording electrode. AEA acting at CB1Rs increased barosensitive neuronal firing in SD versus SHR rats. In addition, discharge of respiratory I neurons, identified by correlation to phrenic nerve discharge, was found to respond more to CB1R activation in SD rats versus SHRs. The data indicate that neuronal function of CB1Rs in the NTS is blunted in SHRs.Grant Funding Source: Suppoted by VA Merit Review I01 BX000481 (JLS), NSF Award IOS 0751613 (CD)