Objective It was designed to observe the effects of ? amyloid protein on the functions of neurotransmitter receptors and to disclose the possible pathophysiological mechanism of Alzheimer disease(AD) mediated by ? amyloid protein and neurotransmitter receptors. Methods Messenger RNA was taken from brains of aged Wistar rats with Promega kits and microinjected into Xenopus oocytes for receptor expression. The currents of expressed receptors and the effects of A? 1 40 on them were detected with the double electrode voltage clamps technique. Results ACh, glutamate, dopamine and GABA receptors were successively expressed in Xenopus oocytes. The currents of these expressed receptors detected with voltage clamps were carried by chloride ions with their equibrillium potentials close to 22 mV. Currents of expressed ACh, glutamate, dopamine receptors in the aged rats decreased more significantly than those in adult young rats. A? had a reverse effect on the functions of ACh and glutamic acid receptors. A? 1 40 enhanced significantly the currents of expressed glutamate receptors when it inhibited markedly the currents of expressed ACh receptors. The currents induced by 10 -4 mol/L ACh decreased from (90.90?14.14) nA to (80.67?16.24) nA ( P

BACKGROUND: More attention has been paid upon the injury effect resulted from the decrease of superoxide dismutase(SOD) activity and increase of malonaldehyde (MDA) content in brain. Whether pig brain peptide solution can pass blood-brain barrier and penetrate into brain tissue and protect brain nerve is still found in limited cases reports. Relevant reports are still rare both in China and abroad.OBJECTIVE: To explore the effect of pig brain peptide solution on SOD activity and MDA content in brain and liver of senile model mice made by D-galactose.DESIGN: Experimental animals-based randomized and controlled experimental observation.SETTING: Institute of Senile Medical of General Hospital of Chinese PLA.MATERIALS: The experimant was made in the Institute of Senile Medical (Chinese PLA key laboratory) of General HosPital of Chinese PLA from February to April 2001. Totally 82 NH mice, weighted from 18 to 22 g, half male and half female, were provided by the Medical Experimental Animal Center of General Hospital of Chinese PLA. These mice were randomly divided into the control group, hige dose group, middle dose group, low dose group, aniracetam group (positive control group), and D-galactose group.METHODS: Each group was given drugs seperately for 6 weeks. The senile mice model was induced by D-galactose. SOD activity of each group was checked with chemiluminescence method and MDA content examined with thiobarbituric acid colourimetry method.MAIN OUTCOME MEASURES: SOD activity and MDA content of mice in each group.RESULTS: Pig brain peptide solution with high and middle doses significantly increased SOD activity[ (30.23 ± 5.23), (29.65 ± 4. 88 );(19. 84 ± 5.79), (16.75 ± 5.32) μkat/g respectively], and decreased MDA content[ (630.00 04; 8(34): 7748-50CONCLUSION: Pig brain peptide solution has obvious antioxidative effect, and has certain protective effects on brain nerve cells and liver cells of senile mice.

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.