Changes induced by sodium cromoglycate in brain catecholamine turnover in morphine dependent and abstinent mice

The effects of sodium cromoglycate (CRO) were studied in relation to the metabolism of brain catecholamines: dopamine (DA) and noradrenaline (NA), and their metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylethyleneglycol (MHPG). CRO was injected SC in control mice, morphine-tolerant mice (tolerance was induced by SC implantation of a 75 mg morphine pellet; CRO was administered on day 4 of addiction) and 30 min before abstinence (withdrawal was induced by SC injection of naloxone (1 mg/kg) on day 4 of addiction). Brain catecholamines and their metabolites were measured using high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD), for DA, NA, DOPAC and HVA, and coupled with fluorescence detection for MHPG. The ratios of DOPAC + HVA/DA and MHPG/NA were kept as an index of DA and NA turnovers, respectively. CRO administered 30 min before naloxone-precipitated withdrawal diminished significantly NA levels in frontal cortex. CRO increased DA turnover in striatum and frontal cortex in naive animals and significantly diminished DA levels in frontal cortex and DOPAC levels in frontal cortex and midbrain in morphine-dependent mice. These findings are discussed in relation to the protective effects of CRO on opiate withdrawal and the effects of CRO on locomotor activity.