Ascorbic acid (AA) as a vitamin and neuromodulator is present in most parts of CNS such as nucleus accumbens shell (Acbsh). This study evaluates the effect of intra-nucleus accumbens shell injection of AA on spatial learning and memory. 35 adult male Wistar rats (220-270 g) were divided into 5 groups: control (intact), sham AA (injected normal saline as AA vehicle) as well as 3 groups of AA (12, 24 and 48 μg/rat/side). After one week of recovery injections were performed. Thirty minutes after each injection the rats were trained in the Morris Water Maze (MWM) and spatial learning and memory parameters were recorded and then analyzed. The results showed that AA at the dose of 48 μg/rat/side significantly increased the travelled distance and latency time to reach the hidden platform in comparison with either control or sham groups (p<0.001). Intra-Acbsh injection of AA led to deficiency of spatial learning.

There are multiple neurotransmitters and neuromodulator systems mediating memory formation among which the endocannabinoid system plays a critical role in the memory formation by modulating the release of many neurotransmitters. Nucleus accumbens appears to have a site in the central of neuronal circuits of the limbic system and to be responsible for the integration and consolidation of inputs from other parts of the brain. In this study the influence of bilateral intra-nucleus accumbens shell microinjections of cannabinoid receptor agents on memory consolidation in adult male rats using passive avoidance task was investigated. The results showed that the intra-accumbens shell microinjection of ACPA as a CB1 receptor agonist (6 ng/rat) immediately after training decreased passive avoidance memory consolidation, while administration of its antagonist (AM251) at different doses did not affect passive avoidance memory consolidation. However, co-administration of AM251 (60 ng/rat) with an effective dose of ACPA prevented the impairment memory consolidation induced by ACPA. These results suggest that the accumbens shell cannabinoid system as a modulating system is involved in aversive memory consolidation including passive avoidance memory.