Capsaicin decreases B-endorphin hypothalamic concentrations in the rat.

Capsaicin has been administered intraventricularly to adult rats and subcutaneously to neonatal rats. Adult rats were killed three, five, seven and fifteen days after capsaicin administration, while rats treated neonatally were killed when six months old. In the adult rats capsaicin induced a decrease in hypothalamic B-endorphin concentrations three, five and seven days after treatment, while they returned to normal values by day fifteen. A decrease in B-endorphin hypothalamic concentrations was also present in rats treated neonatally, while substance P, somatostatin and met-enkephalin concentrations were never affected by capsaicin treatment.