Pregnancy in rats reduced cardiac receptor afferent activity, lacking the higher-frequency spontaneous discharge seen in 24% of receptors in virgin rats (9.91+/-1.19 Hz).
Gestation appears to reduce the activity of cardiac receptor afferents in rats, potentially by increasing the stimulus threshold or inactivating high-frequency discharging receptors.
Reflex effects of cardiac receptor (CR) stimulation are attenuated in pregnant rats. We tested whether CR afferent discharge is reduced during pregnancy by measuring single fiber activity in response to increases in right atrial pressure (RAP) in anesthetized pregnant and virgin rats with sinoaortic denervation. Single fiber activity was isolated from fine filaments of the right cervical vagus nerve. Changes in CR discharge, RAP, and arterial pressure were recorded in response to atrial saline injections (25-300 microl). Resting RAP was similar between groups, and spontaneous CR discharge was similar in pregnant rats (1.95+/-0.21 Hz) and in low-frequency (LF) receptors in virgin rats (1.30+/-0.2 Hz). In virgin, but not pregnant rats, a subset (24%) of CR had higher-frequency (HF) spontaneous discharge (9.91+/-1.19 Hz). During stimulation, the level of RAP above which CR firing increased was significantly higher in pregnant rats, but CR activity was clustered into an LF discharge range. Thus gestation appears to reduce the activity of CR afferents, possibly by increasing stimulus threshold or by selective inactivation of a subset of HF discharging receptors.
Hines et al. (Sat,) conducted a other in Pregnancy. Pregnancy vs. Virgin rats was evaluated on Cardiac receptor afferent discharge in response to increases in right atrial pressure. Pregnancy in rats reduced cardiac receptor afferent activity, lacking the higher-frequency spontaneous discharge seen in 24% of receptors in virgin rats (9.91+/-1.19 Hz).