NMDA Component of the Excitatory Synaptic Transmission of Neurons Containing Serotonin or GABA in the Ventrolateral Subdivision of the Periaqueductal Gray Matter of Mouse

The midbrain periaqueductal gray( PAG) plays a crucial role in the descending pain modulating system.NMDA receptors (NMDARs) and serotonergic and GABAergic neurons have been identified in the PAG and are involved in the descending pain-modulating pathway. We characterized the NMDA component of the excitatory synaptic transmission within the ventrolateral subdivision of the PAG( vlPAG) using a whole cell patch clamp technique and then detected the expression of tryptophan hydroxylase (TPH), serotonin synthesizing enzyme, and glutamate decarboxylase (GAD), GABA synthesizing enzyme to understand thevlPAG intrinsic neurotransmission. The NMDA/non-NMDA ratio and the decay time constant of theNMDA component of the non-serotonergic GABAergic neurons were significantly larger than those of nonserotonergicnon-GABAergic neurons and serotonergic GABAergic neurons. This suggests that the non-serotonergic GABAergic neurons might play an important role in the descending pain modulating system originated from the PAG. The decay time constant of the NMDA component of the non-serotonergic non-GABAergic neuron was significantly greater in the mouse with partial sciatic nerve ligation compared with the control mouse. These results suggest that the subunit composition of the NMDAR in the non-serotonergicnon-GABAergic neurons change during neuropathic pain

Comparison of Remifentanil and Landiolol on Hemodynamic and Plasma Catecholamine Responses to Tracheal Intubation

The purpose of this study is to compare remifentanil with landiolol to examine the effects of hemodynamic and plasma catecholamine responses to tracheal intubation. Sixty patients scheduled for elective surgery were randomly divided into three groups, to receive either normal saline( group C), a 1-minute loading infusion of remifentanil 0.5 m g/kg followed by an infusion of remifentanil 0.25/m g/kg/min during the study(group R), or a 1-minute loading infusion of landiolol 0.125 mg/kg followed by an infusion of landiolol0.04 mg/kg/min during the study (group L). After the 1-minute loading infusion of each drug, anesthesia was induced with intravenous injection of propofol 2 mg/kg, and vecuronium 0.1 mg/kg. Five minutes after the administration of each drug, tracheal intubation was performed within 30 seconds. Mean arterial pressure remained below the baseline value after tracheal intubation in group R, but not in groups L and C.Heart rate significantly increased after tracheal intubation in group C, but not in groups R and L. Plasma concentration of adrenaline remained below the baseline value after tracheal intubation in all groups, but it was significantly lower in group R, compared with other groups. Plasma concentration of noradrenaline significantlyincreased after tracheal intubation in groups L and C, but not in group R. Bispectral index in group R remained lower than that in groups L and C after tracheal intubation. Remifentanil may be preferableto landiolol to provide cardiovascular stability after tracheal intubation