Objective Examine the effect of electrical stimulation of nucleus tractus solitaries (NTS) on cardiac-somatic motor reflex (CMR) that induced by intrapericardial administration of capsaicin to clarify the spinal cord mechanism of NTS involved in cardiac nociception in rat. Methods SD rats were randomly divided into electrical stimulation, control, yohimbine and naloxone group and treated with elecetrical stimulation NTS alone, or with intrathecal injection of vehicle, saline, norepinephrine α2 receptors antagonist (yohimbine), opioid receptor antagonist (naloxone) respectively. Results Electrical stimulation of NTS (10, 20, 50 μA), the CMR response decreased in an intensity-dependent manner (P P >0.05); intrathecal injection of yohimbine (20 μg, 50 μg) or naloxone (50 μg, 100 μg), reversed the inhibition effect of electrical stimulation (P 2 receptors and opioid receptor in spinal cord involved in this descending inhibition, low dose of naloxone has synergetic effect with descending inhibition.
