Jpn. J. Pharmacol. 83 (1), 25-30 (2000)

Paeoniflorin, a Major Constituent of Peony Root, Reverses Muscarinic M₁-Receptor Antagonist-Induced Suppression of Long-Term Potentiation in the Rat Hippocampal Slice

Keiichi Tabata, Kinzo Matsumoto and Hiroshi Watanabe*


Department of Pharmacology, Institute of Natural Medicine, Toyama Medical and Pharmaceutical University,
2630 Sugitani, Toyama 930-0194, Japan
*ﾊTo whom correspondence should be addressed.

Abstract: We previously reported that paeoniflorin but not albiflorin, components of peony root, produced ameliorative effects on scopolamine-induced spatial cognitive impairment in rats. In this study, we examined the effects of paeoniflorin and muscarinic receptor antagonists on long-term potentiation (LTP) of population spike recorded from the CA1 region of rat hippocampal slices. Bath applications of an M₁- and M₂-receptor antagonist scopolamine and a selective M₁-receptor antagonist pirenzepine, at a concentration of 10ﾊmM, significantly suppressed LTP, whereas AF-DX116, a selective M₂-receptor antagonist, failed to affect it. Paeoniflorin (0.1-1ﾊmM), which alone was ineffective on LTP induction, significantly reversed the suppressive effects of scopolamine and pirenzepine (10ﾊmM). In contrast, albiflorin (0.1-1ﾊmM) had no effect on the scopolamine-induced LTP suppression. These results suggest that paeoniflorin reversal of the muscarinic M₁-receptor-mediated inhibition of LTP may be implicated in the ameliorative effect of paeoniflorin on spatial cognitive impairment caused by cholinergic dysfunction.

Keywords: Paeoniflorin, Long-term potentiation (LTP), Hippocampus, Muscarinic M₁-receptor, Scopolamine