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Background: It has been indicated that there is a relationship between vitamin B12 status and cognitive functioning. Measurement of serum vitamin B12 is routinely performed in patients with memory loss during initial diagnosis. Noticing the role of cholinergic system and vitamin B12 on memory, the aim of this experimental study was to examine the effect of the interactions between vitamin B12 and nicotine on memory retention in passive avoidance learning in adult male rats. Materials and Methods: The present study was an experimental one. Drugs, including vitamin B12 (0.01, 0.02, 0.03, 0.05, 0.1, and 1 µg/rat) and nicotine (0.1, 0.5, and 1 µg/rat) were administrated after training session intracerebroventriculary (i.c.v.). The drugs were used (i.c.v.) in a volume of 1µl/rat immediately after the training session. The level of memory retention was evaluated by passive avoidance learning. Twenty-four hours after training, a retention test was performed to determine long-term memory. Statistical analysis was carried out using one-way ANOVA test. Results: The results showed that the administration of vitamin B12 and nicotine significantly increased memory retention in rats. Nicotine significantly increased the response to vitamin B12 in memory retention process. Conclusion: Vitamin B12 through interaction with cholinergic system acts in memory retention process.

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Background and Aim: Anxiety is an adaptation response that is created in response to multiple physiological and environmental stresses. It is clear that involvement of various neurotransmitter systems has important role in the anxiety process. Vitamin C is a water-soluble antioxidant that plays a role in many physiological reactions in the body. On the other hand, nicotine, which increases with tobacco intake, has an anxiogenic effect. Naloxone, as an opioid receptor antagonist, also plays an important role in the development of anxiety behavior. The aim of this study was to investigate the role of naloxone-co-administered vitamin C on anxiety induced nicotine. Materials and Methods: 84 male mice (30 ± 2 gr) were randomly divided into 12 groups. Anxiety test was performed 30 minutes after intraperitoneal injection of drugs by an elevated plus maze apparatus for 5 minutes. Anxiety indices such as percentage of open arm entry (OAE%) and percentage of time staying in the open arm (OAT%) were recorded and evaluated. Findings: In this research, injection of nicotine (0.8 mg/kg, ip) increased anxiety behaviors. Vitamin C (80 mg/kg, ip) improved the nicotine-induced anxiety. This effect of vitamin C was inhibited by ineffective dose of naloxone (4 mg/kg, ip). Conclusion: It seems that vitamin C decreases anxiety behavior of nicotine in the presence of opioid receptors.