Protein kinase-mediated reciprocal modulatory changes in anesthetic sensitivity of (BK)-K+- and GABA-A receptor-gated conductances in guinea-pig sympathetic neurons

(1) The interaction of substance P (SP)-mediated synaptic transmission with general anesthetics remains unknown. (2) Intracellular recordings were obt ained from guinea-pig inferior mesenteric ganglion neurons to study monosyn aptic responses to exogenous SP and GABA. (3) Propofol (1-100 mu M) caused an increase in SP-evoked inward current responses and a concurrent decrease in peak amplitude of the afterspike hyperpolarization of intermittently ev oked action potentials. These effects were occluded by the (BK)-K+-channel- selective blocker charybdotoxin (10 nM), and prevented by the protein kinas e inhibitor staurosporine (100 nM). (4) Propofol also increased GABA-evoked current (I-GABA) responses. (5) When elicited during a SP response, I-GABA was significantly diminished compared to control. In the presence of staur osporine (100 nM), the inhibitory effect of SP upon I-GABA was abolished, a nd the propofol-induced augmentation of I-GABA was significantly increased. (6) Thus, SP-evoked protein kinase activity produced reciprocal changes in anesthetic sensitivity of (BK)-K+- and GABA A-receptor-gated currents of t hese sympathetic neurons. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.