Figure 2.

Electrophysiological identification of the nonmodulated and respiratory-modulated RVLM presympathetic neurons in in situ preparations. Ai, Hyperpolarizing potentials and inhibition of spike discharge frequency (3 superimposed sweeps, no polarizing current, membrane potential, −57 mV) evoked by stimulation of the ipsilateral ADN with bursts of 3 pulses (***). Aii, Antidromic action potentials evoked by stimulation (*) of the T8–T12 segment of the spinal cord. Three superimposed sweeps pretriggered by sEPSPs are shown. The arrow indicates spontaneous excitatory postsynaptic potential preceding spontaneous spikes. Note that spinal stimulation was followed by antidromic responses that occurred ∼6 mV more negative than the threshold at which spontaneous action potentials were induced by the ongoing synaptic activity. Bi, The ADN-evoked potentials (10 averaged sweeps) recorded intracellularly when the firing of the cell was stopped by a continuous negative current (−25 pA). Bii, Reversal of evoked inhibitory postsynaptic potential (holding current of −200 pA) evoked by stimulation of the ADN. Ci–Dii, sEPSPs, measured by hyperpolarizing the neurons, in the nonmodulated (Ci), inspiratory-modulated (Cii), postinspiratory modulated (Di), and inspiratory-inhibited (Dii) RVLM presympathetic neurons.