The nociceptive jaw-opening reflex: Evidence for alpha2 adrenoceptor involvement

摘要: Abstract The ability of alpha adrenoceptor agonists to modulate the tooth pulp stimulation evoked (TPS) jaw-opening reflex (JOR) was investigated in rats and rabbits. Low doses clonidine (6.25–50 μg/kg, IV) significantly increased dEMG thresholds. These effects were antagonized by 2 antagonists (e.g., yohimbine), but not 1 prazosin) or mu receptor naloxone). Polar ST-91 4-hydroxyclonidine) that cross blood brain barrier (BBB) poorly lipophilic ST-587) BBB easily without affect on TPS-JOR. Structures peripheral efferent neurocircuitry JOR digastric muscle neuromuscular junction its motor nerve, mylohyoid) shown be active sites clonidine's effect Treatment with phentolamine (an antagonist crosses BBB) completely initial transient cardiovascular (pressor) altering TPS-JOR effects. Pretreatment reserpine (a catecholamine depleting agent) failed alter affects Our studies suggest adrenoceptors potently such modulation may important understanding trigeminal neuronal circuitries partake pain processing.