Adenosine A1 receptors are involved in the modulation of the rhythmical respiration in neonatal rat brainstem slice in vitro / 生理学报

This study was designed to investigate whether adenosine A1 receptors could modulate primary rhythmical respiration in mammals. Experiments were performed in 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 inspiration-related neurons (I neurons) in mNRF and respiratory rhythmical discharge activity (RRDA) 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). DPCPX induced a significant decrease in the expiratory time and the respiratory cycles, and an increase in the discharge frequency and peak frequency of I neurons in the middle phase of inspiration. However, R-PIA significantly decreased the inspiratory time and integral amplitude as well as prolonged respiratory cycle. Moreover, the discharge frequency and the peak frequency of I neurons were decreased in the middle phase of inspiration, but not in the initial and terminal phases. The effect of R-PIA on rhythmical discharges could be partially reversed by additional application of DPCPX. These results indicate that adenosine A1-receptors are possibly involved in the modulation of rhythmical respiration through the inhibitory synaptic input from I neurons.

Nitric oxide is involved in the modulation of central respiratory rhythm / 生理学报

This experiment was expected to test whether nitric oxide (NO) exerted significant effect on the central respiratory rhythm. Experiments were performed on in vitro brainstem slice preparations from neonatal rats. These preparations include the medial region of the nucleus retrofacialis (mNRF); a part of pre-Bötinger complex, ventral respiratory group (VRG) and dorsal respiratory group (DRG). Respiratory-related burst activities were recorded from hypoglossal nerve rootlets before and during superfusion of the slice preparation with L-Arginine (L-Arg), sodium nitroprusside (SNP) or 7-nitro indazole (7-NI, an inhibitor of NO synthase). After perfusion with L-Arg and SNP, there was no significant change in respiratory rhythmical discharge activity (RRDA), but 7-NI decreased the integral amplitude of burst and inspiratory time. These results indicate that NO may take part in the inspiratory off-switching mechanism and that it also modulates the amplitude of respiratory-related bursts.