Pregnancy decreases GABAergic inhibition of the hypothalamic paraventricular nucleus

Physiology & Behavior 97 (2009) 171–179 doi:10.1016/j.physbeh.2009.02.018 Lyudmyla Kvochina, Eileen M. Hasser, Cheryl Heesch During pregnancy it has been shown that the baroreflex ability to increase sympathetic nerve activity is attenuated in response to low blood pressures. However resting sympathetic tone for heart rate and the vasculature was still elevated during pregnancy. The purpose of this study was to see if tonic GABAergic inhibition in PVN is decreased in response to pregnancy. They used pregnant and non-pregnant female Sprague Dawley rats in order to conduct their study. They microinjected AT1 receptor blocker before GABA A receptor blockade in PVN, they showed attenuation in the increase in BP and RSNA in response to GABA AR blockade. They also added an excitatory amino acid receptor blocker with the AT1 receptor blocker in order to determine the effect it would have on GABA A receptor blockade. They found that the response was to GABA A receptor blockade was completely eliminated in pregnancy. They also added kyn with AT 1 receptor blockade and showed no difference in AT1 receptor blockade alone in pregnancy. They also showed that increases in RSNA in response to GABA A receptor blockade were attenuated in pregnant rats. The conclusion is that GABAergic inhibition of presympathetic nerves in PVN may be decrease which may be the cause of the enhanced resting symapathetic nerve activity. -MD