DELTA-9-TETRAHYDROCANNABINOL INCREASES PRODYNORPHIN AND PROENKEPHALINGENE-EXPRESSION IN THE SPINAL-CORD OF THE RAT

Hypoalgesia induced by cannabinoid drugs has been found to implicate t he opioid system. The effect of five days treatment with Delta-9-tetra hydrocannabinol (THC) was examined on prodynorphin (PDYN) and proenkep halin (PENK) gene expression in the spinal cord of male rats. PDYN and PENK gene expression was estimated measuring by northern blot analysi s mRNA levels in the whole spinal cord, containing perikarya of these neurons. The subchronic treatment with THC (5 mg/kg/day; 5 days; i.p.) produced an increase in PDYN (39%) and PENK (34%) gene expression whe n compared with the vehicle treated group. These results suggest that the effects of THC in the spinal cord involve an increase in opioid ac tivity, and therefore sustain the hypothesis of an interaction between the cannabinoid and opioid systems in this region. (C) 1997 Elsevier Science Inc.