8-OH-DPAT abolishes the pulmonary C-fiber-mediated apneic response to fentanyl largely via acting on 5HT_(1A) receptors in the nucleus tractus solitarius

摘要

Intravenous bolus injection of morphine causes a vagal-mediated brief apnea (~3 s), while continuous injection, via action upon central mu-opioid receptor (MOR), arrests ventilation (>20 s) that is eliminated by stimulating central 5-hydroxytryptamine 1A receptors (5HT_(1A)Rs). Bronchopulmonary C-fibers (PCFs) are essential for triggering a brief apnea, and their afferents terminate at the caudomedial region of the nucleus tractus solitarius (mNTS) that densely expresses 5HT_(1A)Rs. Thus we asked whether the vagal-mediated apneic response to MOR agonists was PCF dependent, and if so, whether this apnea was abolished by systemic administration of 8-hydroxy-2-(di-n-propyl-amino)tetral (8-OH-DPAT) largely through action upon mNTS 5HT_(1A)Rs.