Cognitive and immunohistochemical study on the effect of neostigmine on ketamine induced wistar rats

Background and Objective: Cognitive deficit is one of the symptoms of schizophrenia due to altered acetyl cholinesterase levels and thus treated by cholinesterase inhibitors like neostigmine. We studied the cognitive and immunohistochemical effect of Neostigmine on Ketamine induced cognitive deficit in rats.
Methods: Twenty (20) wistar rats were divided into four groups (n=5). Positive control (group A) received 0.1ml saline; the cognitive deficit groups received 25mg/kg Ketamine for 7days and then divided into B, C, and D groups. The group B and A were sacrificed in day 8, while C and D groups were treated with 0.5mg/kg Neostigmine and negative control  treated  with 0.1ml saline for 21days. T-maze cognitive test was performed on 8th and 21st days. Thereafter they were anesthetized with 50mg/kg thiopental sodium, and aortic perfusion was performed with 4% paraformaldye. The amygdala was stained for GFAP by immune peroxidase method.
Result: The result showed that the T-maze cognitive deficit induced by Ketamine was reversed by Neostigmine as the rat showed increased number of time entries and time spent in the rewarded arm. GFAP expression increased in Ketamine group was decreased by Neostigmine treatment.
Interpretation and Conclusion: Neostigmine ameliorates the cognitive and decrease GFAP expression induced by Ketamine on the amygdala.