Leu-enkephalin content in rat brain during prolonged treatment with imipramine or amitriptyline

The influence of imipramine (IMI) or amitriptyline (AMI) on the level of immunoreactive leu-enkephalin (ir-LENK) in the striatum and hypothalamus was studied in rats. Each drug was given by drinking water once or over periods of 1, 3, 4 and 6 months. The ir-LENK in brain perfusates was measured after 3 or 9 month treatment with IMI. The results obtained indicate that during prolonged administration of IMI the central enkephalinergic system is dynamically changed. We have observed that chronic (but not acute) administration of IMI induced different effects on LENK level in the examined structures than changes caused by treatment with AMI.