Ketamine inhibits presynaptic and postsynaptic nicotinic excitation of identified cardiac parasympathetic neurons in nucleus ambiguus.

摘要: BACKGROUND Ketamine increases both blood pressure and heart rate, effects commonly thought of as sympathoexcitatory. The authors investigated possible central nervous system actions ketamine to inhibit cardiac parasympathetic neurons in the brainstem by inhibiting multiple nicotinic excitatory mechanisms. METHODS used a novel vitro approach study effect on identified preganglionic rat slices. nucleus ambiguus were retrogradely prelabeled with fluorescent tracer placing rhodamine into pericardial sac. Dye-labeled visually for patch clamp recording. tested nicotine-evoked ligand-gated currents spontaneous glutamatergic miniature synaptic (mini) neurons. RESULTS (10 microm) inhibited (1) nicotine (1 microm)-evoked presynaptic facilitation glutamate release (mini frequency, 18 +/- 7% control; n = 9), (2) direct postsynaptic current (27 8% but did not alter amplitude non-N-methyl-D-aspartate currents. alpha Bungarotoxin, an antagonist 7 containing receptors, blocked mini frequency (n 10) amplitude. CONCLUSIONS inhibits receptors responsible facilitating neurotransmitter release, well inward current, does augmentation Such may mediate decrease activity increase rate that occurs ketamine.