腺苷A1受体在双相呼气和吸气神经元电活动中的作用

目的探讨腺苷A1受体对双相呼气神经元和吸气神经元电活动的影响。方法制作新生大鼠体外延髓脑片标本，主要包含面神经后核内侧区(the medialregion of the nucleus retrofacialis，mNRF)，并保留舌下神经根的完整，以改良Kreb’s液灌流脑片，同步记录舌下神经根和双相呼气神经元/吸气神经元的放电活动。在灌流液中分别单独给予腺苷A1受体的特异性拮抗剂8-环戊-1，3-二丙基黄嘌呤(8-cyclopentyl-1，3-dipropylxa nthine，DPCPX)和特异性激动剂R-苯异丙基-腺苷(R—phenylisoprpyl—adeno sine，R-PIA)观察对神经元放电的影响。结果给予腺苷A1受体拮抗剂DPCPX后，双相呼气神经元/吸气神经元的呼吸周期和呼气时程明显缩短，单位放电峰频率显著性增大；给予相应激动剂R-PIA后，双相呼气神经元的呼气时程明显延长，放电频率和积分幅度显著降低，吸气神经元的放电时程和中期放电的频率和峰频率显著性降低，而早期和晚期的放电频率无明显改变。结论腺苷A1受体可能通过影响双相呼气神经元的电活动参与了呼吸时相的转换，并可能介导了吸气神经元的抑制性突触输入。

Effects of adenosine A1 receptors on the discharge activities of biphasic expiratory neurons and inspiratory neurons in vitro brainstem slice from neonatal rats

Objective This experiment was expected to test whether adenosine A1 receptors exerted a significant effect on the discharge activities of biphasic expiratory neurons and inspiratory neurons. Methods Experiments were performed in vitro brainstem slice preparations from neonatal rats. These preparations included the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve rootlets retained. The activity of the biphasic expiratory neurons /inspiratory neurons in mNRF and respiratory rhythmical discharge activity of the hypoglossal nerve rootlets were simultaneously recorded by using microelectrodes and suction electrodes, respectively. Possible roles of adenosine A1 receptors in rhythmical respiration were investigated by administration of adenosine A1 receptor agonist R-phenylisopropyl-adenosine (R-PIA) and its specific antagonist 8-cyclopentyl-1,3- dipropylxanthine (DPCPX) into a modified Kreb s perfusion solution (MKS). Results DPCPX significantly shortened the respiratory cycle and expiratory duration of the biphasic expiratory neurons and inspiratory neurons as well as increased both the peak frequency. On the other hand, R-PIA induced a significant decrease in the discharge frequency and integral amplitude of biphasic expiratory neurons and a prolongation in the expiratory duration. Morever, the discharge duration of inspiratory neurons was shortened, and the discharge frequency was decreased in the middle phase of inspiration, but not in the initial and terminal phases. Conclusion Adenosine A1 receptors are possibly involved in the phase-switching between expiration and inspiration by affecting biphasic expiratory neurons and may modulate the inhibitory synaptic inputs from inspiratory neurons.