Abstract： Objective　To investigate the effects of free radicals (FRs) and amyloid β protein 1-40 (Aβ1-40) on the functions of expressed neurotransmitter receptors (NRs) in Xenopus oocytes.Methods　Total RNA and messenger RNA (mRNA) was prepared from 3-month-old Wistar rat brain tissues with Promega kits and microinjected into maturated Xenopus oocytes (stages Ⅴ-Ⅵ) with 50nl (50ng) for each oocyte. The microinjected oocytes were incubated with modified Bath's solution at 19.0℃±1.0℃ for receptor expression and their currents were recorded with double electrode voltage clamp technique. Superoxide anion free radicals (SAFRs) were produced via a reaction system (HPX/XO) with hypoxanthine (HPX, 0.05mol/L) and xanthine oxidase (XO, 0.1U/L). In order to observe the effects of Aβ and SAFRs on the expressed glutamate receptor, HPX/XO and Aβ1-40 were added to incubation solution at 12h, 24h and 96h before recording.Results　The results showed that the oocytes expressed functional NRs originating from rat brain tissues. These NRs included muscarinic acetylcholine (mACh), glutamate (Glu), dopamine (DA), serotonin (5-HT) and γ-aminobutyric acid (GABA). The current characteristics of expressed receptors were inward currents carried by chloride ion with their equibrilium potentials close to -22mV. The extent of effect on the current of expressed glutamate receptor from rat brain was different among different Aβ concentrations and incubation times. Aβ1-40 at a concentration of 20nmol/L had little effect on the currents of expressed rat brain glutamate receptors up to 24h of incubation period; but the currents of glutamate receptor were significantly decreased (25% off, P<0.01) in the treatment of 60nmol/L Aβ1-40 over 24h. Moreover, when 20nmol/L Aβ1-40 was co-incubated over 12h with SAFRs produced by the reaction system of HPX/XO, it was found that the currents of expressed rat brain glutamate receptors had been changed markedly. When the oocytes were co-treated with 60nmol/L Aβ1-40 and SAFRs over a period of 12h, the currents of glutamate receptor significantly decreased (21% off, P<0.05), and the decreased percentage reached 52% over 24h co-treatment with 60nmol/L Aβ1-40 and SAFRs. In addition, vitamin E had a partial effect against this inhibitory effect.Conclusion　The results suggest that Aβ has a kind of inhibitory effect upon the current of the glutamate receptor, similar to the effects of free radicals. The effects can be antagonized by vitamin E. These imply that Aβ may play a role via inhibiting receptor function in the pathophysiology of Alzheimer's disease.