Recently it has been shown that both local and general anaesthetics can affect immediate early gene (ieg) expression (Hamaya et al. 2000) and it has also been shown that local anaesthetics significantly decrease extracellular regulated kinases (ERKs) 1 and 2 (Kansha et al. 1999). Additionally, these kinases are associated with linking membrane depolarization to gene expression (Ghosh & Greenberg, 1995). Here we examine the effects of the volatile anaesthetic halothane and the barbiturate thiopentone on the expression of ERK1 and -2 in PC12 cells, which are accepted as a useful model for studying the mechanics of calcium-dependent signalling events in the nervous system.

PC12 cells were cultured in T75 flasks in DMEM supplemented with 10 % horse serum, 5 % fetal calf serum, 2 mM l^-1 glutamine and 40 U ml^-1 pencillin and 100 µg ml^-1 streptomycin. Cells were passaged once a week and fed twice a week. Cells were not used after 10-12 passages. The cells were continuously exposed to the anaesthetics for set periods of time and then blotted to detect ERK1 and -2. Western blots were performed as described in Kansha et al. (1999) using precast gels and membranes from Biorad. All data were statistically analysed using ANOVA and Tukey’s post hoc test.

Both anaesthetics had significant effects on total phosphorylated ERK (pERK1 + pERK2). In the presence of 500 µM thiopentone there was a significant increase (P > 0.05) in pERK between 20 and 40 min exposure. This increase was 190 % of control levels after 20 min exposure (n = 5). After 80 min exposure the amount of pERK did not differ significantly from control. In contrast, in the presence of 2 % halothane pERK increased significantly to 140 % of control levels after 60 min exposure, and to 163 % of control levels after 120 min of exposure (P > 0.05, n = 4).

Thiopentone, a barbiturate, significantly stimulated pERK to produce a result comparable with 1 mM ionomycin (we found a 250 % increase after minutes exposure). Halothane, a general anaesthetic, also significantly increased pERK but at a lower level and for a longer period of time. In contrast, Kansha et al. (1999) found that the local anaesthetics dibucaine and tetracaine significantly decreased pERK. Theses results suggest that anaesthetics can have effects on nuclear regulated activity.