NARCOTIC ANALGESICS AND THE REGULATION OF NEURONAL CATECHOLAMINE STORES

Abstract

This chapter presents a study investigating narcotic analgesics and the regulation of neuronal catecholamine stores. This study estimated the turnover rate of cerebellar norepinephrine (NE), spinal cord NE and striatal DM by injecting intravenously 1 mCi/kg of L-tyrosine 3,5-3H (1 mCi/33 nmoles) and by measuring the specific radioactivity of tyrosine, NE or DA. These brain areas were selected because each area contains only dopaminergic or noradrenergic axons. Drugs were injected i.p. 10 min before the radioactive tyrosine and the animals were killed 10 min after the label. Specific radioactivity of tyrosine, NE and DA, and the turnover rate of these amines were determined. Animals were rendered tolerant to and physically dependent on morphine by pellet implantation. Physical dependence was assessed by the naloxone test. The data shows that morphine increases the turnover rate of DA in striatum, but it does not change the turnover rate of spinal cord and cerebellar NE. Moreover, in rats implanted with morphine pellets the turnover rate of striatal DA is normal.