Effect of combination of Phyllanthus emblica, Tinospora cordifolia, and Ocimum sanctum on spatial learning and memory in rats.

Background: There has been a steady rise in number of patients suffering from dementia including dementia associated with Alzheimer’s disease. Effective treatment of Alzheimer’s disease dementia is an unmet medical need. Objective: To evaluate effects of formulation containing combination of Phyllanthus emblica (Pe) and Tinospora cordifolia (Tc) with and without Ocimum sanctum (Os) on learning and memory performance of normal and memory impaired rats in complex maze and compare with effects of Tinospora cordifolia and Phyllanthus emblica alone. Materials and Methods: Wistar rats; either sex (100–150 g) were divided in seven groups Control, Piracetam, Rivastigmine, Tc, Pe, Formulation 1 (Tc + Pe), and Formulation 2 (Tc + Pe + Os).The study was divided in four parts: In part 1 memory enhancement was tested in normal rats. In part 2, 3, and 4 the effects of drugs were tested in Scopolamine‑, Diazepam‑, and Cyclosporine‑induced amnesia. Hebb–Williams maze was used to test for learning and memory. Time required to trace food and number of errors in maze were noted. Results: In normal rats, all test drugs showed significant reduction in time required to trace the food and number of errors after 24 h compared with vehicle control. Formulations 1 and 2 reduced the time required to trace food and number of errors and the results were comparable with positive control groups and comparators Tc and Pe. Formulations 1 and 2 reversed amnesia produced by Scopolamine, Diazepam, and Cyclosporine when compared with vehicle control and showed comparable results with those of positive control groups and comparators Tc and Pe. Conclusion: Formulations 1 and 2 demonstrated nootropic activity and both the formulations showed comparable nootropic activity with that of Tc and Pe alone.

Role of dopamine – D2 receptor in spatial memory retention and retrieval determined using Hebb-williams complex maze.

Effects of bromocriptine and sulpiride were observed on encoding and retrieval of spatial memory in wistar rats using Hebb-Williams complex maze. Rat was placed in entry chamber and allowed to reach reward chamber. Ten trials were given each day per rat for 3 consecutive days. Within-day encoding score indicative of learning and between-day retrieval score indicative of memory were calculated. Effects of bromocriptine and sulpiride were observed on encoding and retrieval of spatial memory. General learning index was calculated to compare the effect on spatial memory between groups. Bromocriptine increased while sulpiride decreased within-day encoding index but had no effect on retrieval index. In general learning index, sulpiride group showed more errors whereas bromocriptine group did not show any difference as compared to control. These results suggest that dopamine D2 receptors are involved in memory encoding but not retrieval. Also general learning is under positive modulation by D2 receptors.