'Binge' cocaine administration induces a sustained increase of prodynorphin mRNA in rat caudate-putamen

Other workers have established that cocaine injections increase the levels of dynorphin peptides in the caudate putamen and substantia nigra of the rat brain. Using a quantitative solution hybridization protection assay for mRNA, we detected a significant increase in the concentration of prodynorphin mRNA in caudate putamen extracts of rats injected with cocaine following a 'binge' administration pattern designed to mimic human cocaine abuse. Increased prodynorphin mRNA was observed at the earliest time-point studied (50 h) and the lowest dose (10 mg/kg/day) of cocaine tested and persisted through the 14 day period studied. No prodynorphin mRNA was detected in the substantia nigra.