Local antagonism of intertrigeminal region metabotropic glutamate receptors exacerbates apneic responses to intravenous serotonin

Unilateral AIDA blockade of the ITR significantly increased the duration of apnea evoked by 5-HT infusion (p < 0.03 for each dose tested) during the 30 s following infusion in a dose-dependent fashion, with the two highest doses resulting in intermittent apneas for at least 10 min following a bolus 5-HT infusion. Similar prolonged increases in CVTT and CVVT with respect to control were associated with ITR AIDA injections. These findings suggest that brief perturbations of vagal afferent pathways can produce ongoing respiratory dysrhythmia, including spontaneous apnea, and that glutamatergic neurotransmission within ITR may be important for damping such disturbances. The present observations also suggest that such respiratory damping may be mediated by mGlu1 receptors. These findings extend our understanding of the role of the intertrigeminal region in modulating respiratory reflexes.