Preventive effect of Teucrium polium on learning and memory deficits in diabetic rats

Abstract

Background: Cognitive impairment occurs in diabetes mellitus. Teucrium polium L. (Lamiaceae) has been used in folk medicine to improve mental performance. Here we hypothesized that chronic treatment with an aqueous extract of Teucrium polium (100, 200 and 400 mg/kg, p.o.) would have an effect on passive avoidance learning (PAL) and memory in control and streptozocin-induced diabetic rats.

Material/methods: Treatments were begun at the onset of hyperglycemia, and PAL was assessed 30 days later. A retention test was performed 24 h (hours) after training. After PAL and memory assessment, animals were weighed and blood samples were drawn for plasma glucose measurement.

Results: Diabetes caused impairment in acquisition of PAL and retrieval of memory. Teucrium polium treatment (200 and 400 mg/kg) improved learning and memory in control rats and reversed learning and memory deficits in diabetic rats. The 100 mg/kg dose did not affect cognitive function. Teucrium polium treatment partially improved the reduced body weight and hyperglycemia of treated diabetic rats, although the differences were not significant compared to non-treated diabetic rats.

Conclusions: These results show that Teucrium polium prevented the deleterious effects of diabetes on PAL and memory. Antioxidant, anticholinesterase and hypoglycemic effects of Teucrium may be involved in the obtained effects. Therefore, Teucrium polium appears to be a promising candidate for memory improvement in diabetes, but this needs confirmation by future clinical studies.

Figure 1

Effects of long-term administration of Teucrium polium extract on the PAL test. The effect of long-term oral administration of extract on the step-through latency (STLa) in the first acquisition trial (A), the number of trials to acquisition (B), step through latency (STLr) in the retention test (C) and the time spent in the dark compartment during the retention test (TDC) (D) between different control (Cont) and diabetic (Diab) groups (n=8). ^a P<0.05, ^b P< 0.01 and ^c P< 0.001 compared to control group. ^d P<0.01 and ^e P<0.001 compared to diabetic group. ^f P<0.001 difference in STLr between 200 and 400 mg/kg extract-treated control rats. Each column and bar represents mean ±S.E.M.