SPINAL-ANESTHESIA BY LOCAL-ANESTHETICS STIMULATES THE ENZYME PROTEIN-KINASE-C AND INDUCES THE EXPRESSION OF AN IMMEDIATE-EARLY ONCOGENE, C-FOS

To understand the biochemical mechanisms involved in spinal anesthesia , we measured protein kinase C (PKC) activity and expression of immedi ate early oncogene protein, c-Fos, in the spinal cord. Spinal anesthes ia was induced in mice using intrathecal injection of either 10 mu L p rocaine or tetracaine (0.067 M/approximate to 2%). Control groups were treated with either saline or ethanol. Animals were killed at 1, 5, a nd 15 min after the injection and the caudal 3 cm of the spinal cord w as processed for biochemical analysis. PKC activity was measured by th e transfer of a phosphate group from [gamma-P-32]adenosine 5'-triphosp hate to the threonine group on a synthetic peptide specific for PKC. W estern blot analysis was used to detect changes in c-Fos protein expre ssion. When compared to saline-treated controls, PKC activity was incr eased significantly (P < 0.0005) in procaine- and tetracaine-treated g roups whereas ethanol decreased PKC activity. The less lipid-soluble p rocaine produced a larger increase in PKC activity than did the more l ipid-soluble tetracaine. Moreover, parallel to the effect on PKC activ ity, procaine was more potent than tetracaine as a c-Fos inducer. Thes e results implicate some role for a PKC- and c-Fos-dependent pathway i n the mechanism of spinal anesthesia. However, these results also demo nstrate a lack of correlation between an increase in PKC levels and ei ther potency or lipid solubility of the anesthetics. The increased PKC activity may not be the sole mechanism for spinal anesthesia. These d ata on the effects of local anesthetics on PKC activity and c-Fos in v ivo are of relevance for studies aimed at delineating the biochemical basis of spinal and epidural anesthesia.