Figure 3. Neuronal responses to pentobarbital are altered in the medulla but not cortex of pregnant animals.

Spontaneous activity of neurons in the VRC including rVRG, PreBötC, and BötC are insensitive to pentobarbital (300 µM) during pregnancy. A, Mean normalized firing rate of VRC (n = 37 closed circles) and CTX (n = 47, open squares) neurons from virgin female rats (n = 5 animals) in response to 300 µM pentobarbital (applied at vertical bar, t = 30 min). B, Pentobarbital had equivalent effects on VRC (n = 62) and CTX (n = 37) neurons from male rats (n = 6 animals). C, Pentobarbital (solid vertical line) failed to depress spontaneous activity of VRC neurons (n = 31) from pregnant animals (n = 4), yet inhibited CTX neurons (n = 26) in the same animals. Neuronal activity was modulated by barbiturate insensitive GABA_ARs, as 20 µM muscimol (dashed vertical line) rapidly silenced VRC neurons. D, This effect is reversible as both VRC (n = 51) post partum animals (n = 4) were inhibited by pentobarbital. E, Quantification of the normalized spontaneous activity of CTX (filled bars) and VRC (open bars) after 60 min of pentobarbital (300 µM) application. Single unit activity was normalized to mean baseline activity for that neuron (time 0–30 min). * denotes significantly different from virgin female. p<0.05.