Neural Activation by Milnacipran and Memory Extinction

Hisahito Ishida, Masaaki Iwata, Yukihiko Shirayama, Katsumasa Muneoka

Department of Anatomy I, Showa University School of Medicine, Tokyo, Japan.
Department of Neuropsychiatry, Faculty of Medicine, Tottori University, Tottori, Japan.
Department of Psychiatry, Teikyo University Chiba Medical Center, Chiba, Japan.

DOI: 10.4236/jbbs.2012.22016                

Abstract

Background: Among neurotransmitter influencing memory formation, the noradrenergic system has been recognized as an important system. Memory formation involves various regions including the prefrontal cortex, hippocampus, amygdala and septum. Method: We investigated the effects of milnacipran on passive avoidance task and evaluated Fos counting in the prefrontal cortex, hippocampus, septum, amygdala and nucleus accumbens. Results: The milnacipran-treated rats (20 mg/kg, 4 days) showed a significant decrease in the number of Fos-immunoreactive cells in the infralimbic portion of prefrontal cortex, the shell portion of nucleus accumbens and the CA1 region of hippocampus, but a significant increase in the Fos counts in the lateral septum with no changes in the Fos counts in the striatum and amygdala. The milnacipran-treated rats showed amelioration in memory extinction (although not statistically significant), but not in memory acquisition and consolidation in the passive avoidance test. Conclusion: The differential activation of the brain regions might be possible sites for ameliorating memory extinction as well as antidepressant effects.

Keywords

Milnacipran; Passive Avoidance Task; Prefrontal Cortex; Nucleus Accumbens; Hippocampus; Septum

Conflicts of Interest

The authors declare no conflicts of interest.

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