# Birch Sap Preserves Memory Function in Rats by Enhancing Cerebral Blood Flow and Modulating the Presynaptic Glutamatergic System in the Hippocampus

## TL;DR

Birch sap improves memory in rats by boosting brain blood flow and enhancing synaptic function in the hippocampus.

## Contribution

This study reveals that birch sap enhances memory via cerebral blood flow and presynaptic glutamatergic modulation in the hippocampus.

## Key findings

- Birch sap-treated rats showed significantly shorter time and distance to reach the platform in the MWM test.
- Birch sap increased cerebral blood flow and evoked glutamate release in hippocampal synaptosomes.
- Birch sap elevated presynaptic protein levels and increased synaptic vesicle numbers in the hippocampus.

## Abstract

As the average age of the population increases, memory impairment has become an increasingly prevalent issue. This study investigates the effects of 14 days of oral birch sap administration on memory functions in healthy rats using the Morris water maze (MWM) test and explores the underlying mechanisms. A compositional analysis revealed that birch soap is rich in polysaccharides, specifically a low-molecular weight polysaccharide (MW 1.29 kDa), and exhibits no hepatotoxicity or renal toxicity at the tested dose. The results from the MWM test demonstrated that the time and distance required to reach the platform were significantly shorter in the birch sap-treated group compared to the control group, suggesting that birch sap supports memory preservation. Moreover, rats treated with birch sap showed improved cerebral blood flow compared to the control rats. Additionally, in hippocampal nerve terminals (synaptosomes), rats treated with birch sap exhibited a significant increase in evoked glutamate release, as well as elevated levels of presynaptic proteins, including vesicular glutamate transporter 1 (VGluT1), synaptophysin, synaptobrevin, synaptotagmin, syntaxin, synapsin I, and the 25 kDa synaptosome-associated protein (SNAP-25). Transmission electron microscopy also revealed a notable increase in the number of synaptic vesicles in hippocampal synaptosomes of the birch-sap-treated rats. These findings suggest that birch sap enhances hippocampal presynaptic glutamatergic functions and cerebral blood flow, contributing to its memory-preserving effects in rats.