The Effect of Treatment with Imipramine and/or Tryptophan after Chronic Stress on the Serotonergic Immunoreactivity in Rat Raphe Nucleus

Kim, Myoung Soon; Lee, Chang Hyun

Abstract

These experiments were performed to investigate the effect of saline, stress, imipramine, stress -imipramine and/or stress -tryptophan on serotonin immunoreactivity in raphe nucleus of the rats (200 ~220 g, body weight). The animals were injected i.p. with imipramine (15 mg/kg) and tryptophan (15 mg/kg) after electric shocks for 20 days. The result by immunohistochemical methods were as follows; 1. Serotonin -immunoreactive neurons in the raphe nucleus of midbrain were significantly increased in stress treated group compared to saline treated group. 2. Serotonin -immunoreactive neurons in the raphe nucleus of midbrain were decreased in imipramine treated group compared all the other group. 3. Serotonin -immunoreactive neurons in the raphe nucleus of midbrain were significantly decreased in stress -imipramine treated group compared to stress alone treated group but were significantly increased in stress -imipramine treated group compared to imipramine treated group. 4. Serotonin -immunoreactive neurons in the raphe nucleus of midbrain were significantly increased in stress -tryptophan treated group compared to stress alone and saline treated group. These experiments indicated that serotonin immunoreactive neurons in raphe nucleus of midbrain were increased due to the activation of stress and decreased by suppresing activation of stress through imipramine treatment.