Activation of 5HT2A receptors alters temporal and spectral characteristics of phrenic nerve discharge in arterially‐perfused adult rat

Abstract

Previous studies in the in vitro transverse medullary slice have demonstrated that activation of serotonergic 5HT2A receptors increases inspiratory burst amplitude and frequency as well as the incidence of augmented (sigh) bursts. The effects of 5HT2A receptor activation in a more intact (and mature) respiratory neuroaxis, and its influence on the spectral dynamics underlying inspiratory motor discharge remains to be identified. Therefore, we examined the effects of 5HT2A receptor activation using DOI (1 μM) on phrenic nerve discharge in 7 arterially‐perfused adult rat preparations. Perfusion with DOI increased phrenic burst frequency from 14.5±2.9 to 31.7±1.9 bpm (P=0.003), which was mediated by a decrease in both TI (from 865+77 to 708+30 ms; P=0.09) and TE (from 4.4+0.9 to 1.3+0.1 s; P=0.015). Phrenic burst amplitude was also decreased during perfusion with DOI. Spectral activity was also modified during perfusion with DOI, such that the onset of both medium (MFO) and high (HFO) frequency oscillations was shifted to and earlier time point in the phrenic burst; power of the MFO peak was also decreased. These findings demonstrate a modulatory role for serotonin acting on the 5HT2A receptor in establishing burst timing and spectral dynamics of phrenic nerve discharge. Supported by NS045321