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.
Highlights
Depression often demonstrated recurrent considering the past, indicating ameliorated memory extinction
We investigated the effects of milnacipran on passive avoidance task and evaluated Fos counting in the prefrontal cortex, hippocampus, septum, amygdala and nucleus accumbens
In the subsequent one-tailed Mann-Whitney test, the milnacipran-treated rats showed a trend for amelioration in memory extinction (168 h later), but not in the memory acquisition (1.5 h later) and consolidation (24 h and 48 h later), when compared to saline-treated controls (Figure 1)
Summary
Depression often demonstrated recurrent considering the past, indicating ameliorated memory extinction. 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 ( 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
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