Neurons of the rostral para-ambiguual field have activity correlated to the 10-Hz rhythm in sympathetic nerve discharge of urethane-anesthetized cat

Abstract

Using the techniques of time domain correlation (mid-signal spike-triggered averaging) and frequency domain correlation (neuron-to-nerve coherence), 24% (54) of a sample of 229 neurons of the rostral para-ambiguual field have shown to have activity correlated to the 8- to 13-Hz rhythm in the inferior cardiac sympathetic nerve discharge (SND) of urethane-anesthetized cat. This correlation existed in both baroreceptor-innervated and -denervated animals. Of the correlated neurons, 37% (20) were non-rhythmically firing and displayed flat autospectra, while 63% (34) fired rhythmically and contained well-defined peaks in their autospectra. The group firing rate of these neurons was 4.3±0.4 spikes/s, indicating that they are not pacemaker neurons for the 10-Hz SND rhythm. The group time of firing of these neurons to the next peak of the SND slow wave was 52±4 ms. Correlation of the activity of medullary neurons with the 8–13-Hz rhythm of the SND was previously claimed only for rostral ventrolateral medulla, caudal raphe, and rostral caudal ventrolateral medulla. This present finding suggests that this behavior may be more widely spread throughout the medulla.