The effects of central delivery of a positive allosteric modulator of GABA_A receptors upon stress and hypertension in Schlager hypertensive mice

Abstract

Hypertensive Schlager mice (BPH/2J) have neurogenic hypertension associated with abnormal reactivity of neurons in the forebrain integrating the response to aversive stress. We found that they also have functional and molecular differences in GABAA receptors compared to their normotensive counterparts (BPN/3J). Allopregnanolone is an endogenous neurosteroid reduced by chronic stress and when administered, decreases anxiety by positive allosteric modulation of GABAA receptors. We therefore compared the effect of chronic intracerebroventricular allopregnanolone and its vehicle on blood pressure and stress reactivity in BPH/2J and BPH/3J mice. Implantation of telemetric probes enabled continuous recordings of blood pressure (BP) at rest and during aversive stressors (restraint and dirty cage switch stress). Two weeks of allopregnanolone reduced MAP (‐9.8±4.3mmHg) and the depressor response to ganglionic blockade (‐10.5mmHg) in BPH/2J but had little effect in BPN/3J. Furthermore, allopregnanolone selectively reduced the pressor response to restraint stress by 27.4% in BPH/2J mice. The selective antihypertensive and stress inhibitory effects of allopregnanolone in BPH/2J mice suggests that allosteric modulation of GABAA receptors has therapeutic potential to treat stress related hypertension.