The Effect of Melatonin Injection into Rat Brain Stem with Chronic Stress on Serotonergic Immunoreactivity

Kim, Myoung Soon

Abstract

These experiments were performed to investigate the effect of saline, melatonin, stress, stressed-melatonin on serotonin immunoreactivity in rat brain stem. The animals were injected with melatonin (1 mg/kg, i.p.) after electric shocks for 15days. The results were as follows; 1. Serotonin immunoreactive neurons in brain stem (the number of staining neuron & the stain intensity in dorsal raphe nucleus of midbrain, the stain intensity in nucleus tractus solitarius and dorsal raphe nucleus of vagus nerve in medulla oblongata) were decreased in melatonin treated group compared with all the other groups. 2. Serotonin immunoreactive neurons in brain stem (the number of staining neuron & the stain intensity in dorsal raphe nucleus of midbrain, the stain intensity in nucleus tractus solitarius and dorsal raphe nucleus of vagus nerve in medulla oblongata) were significantly increased in stressed group compared with all the other groups. 3. Serotonin immunoreactive neurons in brain stem(the number of staining neuron & the stain intensity in dorsal raphe nucleus of midbrain, the stain intensity in nucleus tractus solitarius and dorsal raphe nucleus of vagus nerve in medulla oblongata) were significantly decreased in stressed-melatonin treated group compared with only stressed group but were significantly increased compared with melatonin treated group. These experiments indicate that serotonin immunoreactive neurons in dorsal raphe nucleus of midbrain were increased, due to the activation of stress, and decreased when the activating of stress is suppressed through melatonin treatment.