Biochemical and functional evidence for the control of pain mechanisms by dehydroepiandrosterone endogenously synthesized in the spinal cord

Abstract

We investigated the role and mechanism of action of dehydroepiandrosterone (DHEA) produced by the spinal cord (SC) in pain modulation in sciatic-neuropathic and control rats. Real-time polymerase chain reaction (PCR) after reverse transcription revealed cytochrome P450c17 (DHEA-synthesizing enzyme) gene repression in neuropathic rat SC. A combination of pulse-chase experiments, high performance liquid chromatography (HPLC), and flow-scintillation detection showed decreased DHEA biosynthesis from pregnenolone in neuropathic SC slices. Radioimmunoassays demonstrated endogenous DHEA level drop in neuropathic SC. Behavioral analysis showed a rapid pronociceptive and a delayed antinociceptive action of acute DHEA treatment. Inhibition of DHEA biosynthesis in the SC by intrathecally administered ketoconazole (P450c17 inhibitor) induced analgesia in neuropathic rats. BD1047 (sigma-1 receptor antagonist) blocked the transient pronociceptive effect evoked by acute DHEA administration. Chronic DHEA treatment increased and maintained elevated the basal nociceptive thresholds in neuropathic and control rats, suggesting that androgenic metabolites generated from daily administered DHEA exerted analgesic effects while DHEA itself (before being metabolized) induced a rapid pronociceptive action. Indeed, intrathecal administration of testosterone, an androgen deriving from DHEA, caused analgesia in neuropathic rats. Together, these molecular, biochemical, and functional results demonstrate that DHEA synthesized in the SC controls pain mechanisms. Possibilities are opened for pain modulation by drugs regulating P450c17 in nerve cells.