Respiratory activation of the genioglossus muscle involves both non-NMDA and NMDA glutamate receptors at the hypoglossal motor nucleus in-vivo

The hypoglossal motor nucleus (HMN) transmits respiratory drive to the genioglossus (GG) muscle of the tongue. From in-vitro studies the mechanism of this transmission is thought to rely almost exclusively on non- N-methyl-D-aspartate (non-NMDA) but not NMDA glutamate receptor activation. The current study tests the hypothesis that both non-NMDA and NMDA receptors contribute to respiratory drive transmission at the HMN in-vivo. Experiments were performed in anesthetized adult rats. Microdialysis perfusion of either NMDA or non-NMDA receptor antagonists into the HMN dose-dependently reduced respiratory-related GG activity. These effects were found to be pharmacologically and regionally specific. In addition, the activities of these receptors were related to the baseline level of respiratory drive. These results show that both NMDA and non-NMDA glutamate receptors at the HMN are involved in transmission of the respiratory drive signal to the GG muscle in-vivo.