tracted with MeOH-water (1: 1, 501 x 4) for 4 days (each extraction) at room temperature. The aqueous MeOH solution was concentrated under reduced pressure to give the extract (2.7 kg) which was chromatographed over cellulose (5.0 kg). The active water eluate (410 g) was dialyzed with cellulose tubings (Visking, 36/32) against water for 10 days to afford the non-dialyzable portion (69.6 g). Successive chromatography of the nondialyzable portion over DEAE-cellulose (4.0 ID x 45 cm) with water, over Sepharose 6B (4.0 ID x 95 cm) with 0.1 N NaCI, over DEAE-Toyopearl 650M (4.0 ID x 45 cm) with water containing NaCl (0-* 1 M120 h) and over Sephacryl S-200 (4.0 ID x 95 cm) with 0.1 M Tris-HC1 buffer (pH 8.0) containing 0.5 M NaCI yielded moran A.
1 The antinociceptive action of mesaconitine (MA) microinjected into the nucleus reticularis gigantocellularis (NRGC), the nucleus reticularis paragigantocellularis (NRPG), the periaqueductal gray (PAG) or the lumbar enlargement was investigated in rats by use of the tail immersion test. In addition, the effects of P-adrenoceptor antagonists and an a-adrenoceptor antagonist administered intrathecally (i.t.) on the antinociceptive action of MA given into the NRPG were also examined by the tail immersion test. 2 MA (50, 100 ng per rat) microinjected into the NRGC, the NRPG, the PAG and the lumbar enlargement increased the response latency in rats in a dose-dependent fashion. MA (50 ng per rat) microinjected into neighbouring sites, the nucleus reticularis parvocellularis, the nucleus originis nervi abducentis and the fasciculus longitudinalis medialis, elicited no significant effect. 5 It is concluded that the NRGC, the NRPG, the PAG and the lumbar enlargement are involved in the sites of the antinociceptive action of MA and that the antinociceptive effect of MA administered into NRPG is elicited by activation of the inhibitory noradrenergic neurones from the NRPG in particularly via P-receptor-mediated effects of noradrenaline.
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