Seasonal changes in monoamine levels during morphine withdrawal syndrome and its prevention with baclofen

A. KEMMLING, S. DIAZ, G. BALERIO

Buenos Aires

Congreso; Joint Meeting of the International Society for Neurochemistry (ISN) and the American Society for Neurochemistry (ASN).; 2001

SEASONAL CHANGES IN MONOAMINES LEVELS DURING THE MORPHINE WITHDRAWAL SYNDROME AND ITS PREVENTION WITH BACLOFEN. A. Kemmling, S. Diaz, G. Balerio. Cát. de Farmacología, F F Y B (UBA) ININFA (CONICET), Junín 956 5º piso (1113), Buenos Aires, Argentina.      The aim of the present study was to compare the seasonal (summer and winter) changes in the monoamines and its metabolites levels in various brain regions of male mice during the morphine (MOR) withdrawal syndrome and its prevention with baclofen (BAC). Swiss-Webster albino mice (27-33g) received MOR (2 mg/kg, i.p.), for 9 days. On the tenth day, the dependent animals were divided into two groups: one received naloxone (NAL) (6 mg/kg, i.p.) 60 min after the last dose of MOR, to precipitate the abstinence syndrome; the other group received BAC (2 mg/kg, i.p.) followed by NAL (6 mg/kg, i.p.), injected 30 and 60 min after the last dose of MOR, respectively. Ten minutes after this treatment, mice were sacrificed and the striatum (ST), the cortex (CO ) and the hippocampus (HP) were dissected to determine the endogenous levels of dopamine (DA), 5-hydroxytryptamine (5-HT) and its metabolites using HPLC with electrochemical detection. Summer: DA, dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA) concentrations in the ST of the abstinence group decreased by 49.3% (p<0.001), 67.9% (p<0.01) and 34.2% (p<0.01), respectively. BAC prevented the changes in DA and DOPAC levels, but not in the HVA levels. No differences were observed in the 5-HT and 5-HIAA levels between the experimental groups. The DA in the CO of the abstinence group decreased by 63.07% (p<0.05). BAC prevented  the decrease in DA levels. No differences were observed in the DOPAC, HVA, 5-HT and 5-HIAA levels between the experimental groups. Winter: there were no differences in DA and its metabolites in the ST of the abstinence group while the 5-HT and the 5-HIAA decreased by 31.22% (p<0.001) and 42.01%  (p<0.001) respectively. BAC did not prevent the decrease in 5-HT and 5-HIAA levels. There were no differences in the CO and the HP between the experimental groups in any of the monoamines and metabolites. In conclusion, an alteration of dopaminergic and serotoninergic neuron activity in different areas of the brain, would play an important role in the expression of the MOR withdrawal syndrome during the summer and winter respectively.