Effects of Ascorbic Acid on the Amplitude of Ventral Tegmental Area Field Action Potential in Morphine-Exposed Rats (An Electrophysiology Study)

Introduction & Evidences have indicated that the Ventral Tegmental Area (VTA) is the major source of dopamine (DA) neurons projecting to cortical and limbic regions involved in cognitive and motivational aspects of addiction. Also, studies have indicated that the Ascorbic acid (vitamin C) can reduce the dependency symptoms of opioids such as morphine via effect of activity on dopaminergic neuron in VTA. For this reason, the aim of this study was to assess the effects of ascorbic acid on the amplitude of Ventral Tegmental Area field action potential in morphine-exposed rats. Forty male Wistar’s rats were used in this experimental study conducted at Yasuj University of Medical Sciences in 2010. Animals were randomly divided into four groups after electrode implantation and recovery period: 1. No- Vit C and No-Addicted group (nVitC.nA) 2. Vit C and No-Addicted group (VitC.nA) 3. No- Vit C and Addicted group (nVitCA) 4.Vit C and Addicted (VitC.A), The Vit C groups received 500 mg/kg of Vit C during 20 days. For addicted groups morphine was administrated once daily for 20 days. In the 20th day, the field potential recording was accomplished. Two-way ANOVA was used for data analysis followed by the Tukey test for post hoc analysis. Results were considered significant at P < 0.05. This study shows the exposure to morphine declined the power of Delta and Beta bands (p<0.05) and Vit C solely enhance power of Theta and Beta (p<0.05, p<0.001) in VTA nuclei. Furthermore, Vit C could alter power of some bands which were affected by morphine. Therefore it seems that Vit C has an increasing effects on them (p<0.05). Although the effect of Vit C on power of the VTA bands is not well known, but it is supposed that this phenomenon can be related to alteration in activity of dopaminergic neuron in the brain.