Suprachiasmatic nuclei monoamine metabolism of glucose tolerant versus intolerant hamsters

A critical role for temporal organization of dopaminergic and serotonergic activities within the suprachiasmatic nuclei (SCN) in the regulation of per ipheral glucose metabolism has been postulated. This study employed in vivo microdialysis to investigate the temporal extracellular profiles of dopami ne and serotonin metabolites in the SCN of freely behaving naturally glucos e tolerant and intolerant Syrian hamsters. Microdialysis samples from the r ight SCN of awake, glucose tolerant or intolerant hamsters held on 14 h dai ly photoperiods were collected every 2 h over a 24 h period and assayed via HPLC for the metabolites of dopamine: homovanillic acid (HVA) and serotoni n (5-hydroxyindolacetic acid, 5-HIAA). Among glucose tolerant hamsters, dai ly rhythms of SCN HVA and 5-HIAA were observed with coincident plateaus thr oughout the nocturnal phase of the day (both p < 0.01), Relative to glucose tolerant hamsters, glucose intolerant animals exhibited a loss in the dail y rhythm of SCN HVA (p < 0.0001) and 5-HIAA (p < 0.02) due to marked reduct ions (70%) throughout the 24 h period in HVA levels and comparative decreas es (35%) in nocturnal peak levels of 5-HIAA. These findings demonstrate tha t daily profiles of extracellular dopamine and serotonin activities in the SCN, known to influence glucose metabolism, differ between glucose tolerant and intolerant hamsters. NeuroReport 10:2073-2077 (C) 1999 Lippincott Will iams & Wilkins.