Effects of acute and chronic administration of MCI-225, a new selective noradrenaline reuptake inhibitor with 5-HT3 receptor blocking action, on extracellular noradrenaline levels in the hypothalamus of stressed rats.

In the present study, we investigated the effects of acute and chronic systemic administration of MCI−225(4−(2−fluorophenyl)−6−methyl−2−(1−piperazinyl)thieno[2, 3−d]pyrimidine monohydrate hydrochloride), a newly−developed selective noradrenaline(NA)reuptake inhibitor with 5−HT3−receptor−blocking action, on extracellular NA levels in the hypothalamus of stressed and non−stressed rats by utilizing intracerebral microdialysis.Acute administration of MCI−225(3 and 10 mg/kg, p.o.)significantly and dose−dependently increased extracellular NA levels in the hypothalamus in non−stressed rats.Footshock for 20 min also significantly increased NA levels in the hypothalamus of both groups of rats pretreated with vehicle and MCI−225.Although chronic administration of MCI−225(3 or 10 mg/kg, p.o.for 14 days)did not alter the basal extracellular NA levels in the hypothalamus, the stress−induced increases in extracellular NA levels were significantly lower in rats chronically treated with MCI−225(10 mg/kg)than those of rats pretreated with vehicle for the same period.The increase in extracellular NA levels induced by MCI−225 challenge(3 or 10 mg/kg, p.o.)were not different between rats chronically treated with MCI−225 or vehicle.These results suggest that MCI−225 enhances extracellular NA levels in the hypothalamus in both non−stressed and stressed rats by inhibiting NA uptake and that chronic systemic administration of MCI−225 did not alter basal extracellular NA levels, but reduced the increase in NA release caused by footshock stress.These data suggest the possibility that MCI−225 might possess anxiolytic and/or antidepressant properties.