摘要
应用膜片箝"全细胞"电流记录方法，研究了垂体腺苷酸环化酶激活肽（PACAP）对新生大鼠小脑颗粒细胞高电压激活（HVA）的钙电流作用。实验结果发现：PACAP－38、PACAP－27能明显增加小脑颗粒细胞钙电流的幅值，两者增加钙内流的效应无显著差异，并且都具有脱敏现象；而出于同一家族的血管活性肠肽（VIP）对此电流却没有任何影响。当记录电极内加入GTPγS后，PACAP增加钙电流的效应成为不可逆；而细胞内液加入GDPβS或预先用百日咳毒素孵育细胞12h后，PACAP的钙通道激活作用完全消失。此外，细胞内应用cAMP和磷酸二酯酶抑制剂3－isobutyl－1－methylxanthine（IBMX），既不影响钙通道本身的活动，也不修饰PACAP增加颗粒细胞钙通道电流的效应。我们的结果提示：新生大鼠小脑颗粒细胞上存在着具有功能意义的PACAP受体，该受体被PACAP－38和PACAP－27激活后可增加细胞膜上钙通道的开放，促进钙内流。PACAP的这种作用与百日咳毒素敏感的G蛋白偶联，但并不依赖腺苷酸环化酶参与的第二信使系统。
The effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on calcium current in primary cultured cerebellar granule cells was Investigated by using the 'whole-cell' recording or patchclamp technique. The results showed that PACAP-38 and PACAP-27 reversibly increased calcium current through high-voltage activated(HVA) calcium channels, but had no effect on its activation kinetics. The effects of PACAP showed a desensitization. The effect or PACAP became irreversible when pipette solution contained GTPYS. In contrast, addition of GDPpe to the intracellular solution or pre-incubated with pertussis toxin (PTX) abolished the effect of PACAP on the HVA calcium current. In addition, the effect of PACAP on the calcium channels was not modified by cAMP. Our results indicated that in cultured granule cell from neonatal rat cerebellum,a pertussis toxin-sensitive G protein was implicated in the coupling of PACAP receptor to activation of calcium channels, In belch the adenylate cyclase system was not Involved.
