Naloxone inhibition of the carotid sinus nerve reflex in the nucleus of the solitary tract of the cat.

By applying the specific opiate antagonist naloxone to the lateral portion of the nucleus tractus solitarii of the cat, we not only rapidly inhibited the evoked field potentials elicited by stimulation of the ipsilateral carotid sinus nerve (CSN), but also blocked hypotension and bradycardia induced by CSN stimulation. These findings suggest that some opiates may be neurotransmitters of the primary myelinated fibers of the CSN which mediate hypotension and bradycardia.