Drug-Induced Epigenetic Changes Produce Drug Tolerance
Figure 3
Sodium Butyrate Causes a Tolerant-Like Phenotype and Induces slo Levels
(A) slo mRNA levels in Canton S (CS) heads were measured by real-time RT-PCR with C1 primers that only amplify neural slo transcripts. Six hours after BA sedation, slo mRNA increased approximately 50% compared with nonsedated flies. Sodium butyrate consumption induced slo expression about 2-fold. BA sedation of sodium butyrate–fed flies did not further increase slo mRNA abundance (n = 4; p < 0.05, Student t-test).
(B) A tolerance assay showed that flies sedated with BA recover more rapidly after their second sedation than after their first sedation (24 h between sedations). Shown are recovery curves of a population of age-matched females after their first (blue) and their second (red) sedation. Plotted are the percentage of flies that have returned to wall climbing. Counts were made at 30-s intervals. The inset shows that the sedated population has higher neural expression of slo mRNA as measured by real-time PCR.
(C) The curves show the recovery from BA sedation of flies that consumed food containing 0.05 M sodium butyrate (0.05MSB; red) and the recovery of flies that consumed the same food without sodium butyrate (0MSB;blue). The consumption of the HDAC inhibitor, sodium butyrate, mimics the tolerance phenotype shown in (B). The inset shows that neural expression of slo is increased by sodium butyrate consumption relative to the matched control.
(D) Flies that had been fed sodium butyrate were sedated once (blue) or twice (red, 24 h between sedation) with BA. Both populations recovered from sedation at the same rate. The inset shows the mRNA expression level from slo. Notice that BA sedation plus sodium butyrate does not enhance slo expression more than sodium butyrate consumption alone. For all insets, slo mRNA abundance has been normalized to the cyclophilin 1 internal control. For all plots, the significant differences between curves was determined by log-rank test (for [B], [C], and [D], n = 45; a single asterisk [*] indicates p < 0.05, and double asterisks [**] indicate p < 0.01).