Multielectrode recording of respiratory neuronal activities in pontine microcircuits

Abstract

Recent studies showed that the pontine pneumotaxic region plays an important role in integrating inputs from vagally-mediated pulmonary mechanoreceptors that modulate the respiratory rhythm. To characterize the neuronal microcircuits underlying this process, we recorded simultaneously the extracellular activities of multiple pontine pneumotaxic neurons using a tungsten microelectrodes array with a multichannel data acquisition system from urethane-anesthetized, bi-vagotamized, paralyzed and servo-ventilated adult rats. The neuronal responses to vagal electrical stimulation (80 Hz, 20-40 μA, 1 min) were analyzed. Of a total of 452 dorsolateral pontine neurons recorded in 22 rats, 61 units showed respiratory-modulated rhythmic activities with either inspiratory, expiratory, or phase-spanning discharge patterns, sometimes with superimposed tonic discharge. Pairwise cross-correlation analysis identified 16 (out of total 256) neuronal pairs showing short-latency offset peaks suggesting functional correlations among them. Vagal stimulation attenuated or suppressed the rhythmic activities in most respiratory-modulated neurons (n=53) and promoted tonic discharges in others (n=8). Gravitational transformation of ensemble spike-train activities before, during and after vagal stimulation revealed functional convergence or divergence of respiratory neuronal responses. Results showed that pontine respiratory neurons displayed a multiplicity of rhythmic patterns with differing responsiveness to vagal stimulation. Supported by NIH grants HL67966 and HL072849.