Murphy M G, Moak C M, Byczko Z, MacDonald W F
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
J Neurosci Res. 1991 Dec;30(4):631-40. doi: 10.1002/jnr.490300406.
The regulation of intracellular cyclic AMP (cAMP) formation by adenosine (Ado) and its analogues has been examined in primary cultures of rat-brain astrocytes and neurons. In the presence of the phosphodiesterase inhibitor, Ro 20-1724, basal levels of cAMP ranged from 40-120 pmol/mg protein in both cell types. Levels were not altered by treating the cells with Ado deaminase, which suggested that they did not produce appreciable amounts of endogenous Ado under standard culture conditions. In the astrocytes, microM quantities of agonists increased cAMP up to 30-fold higher than basal values; the relative potencies were typical of an A2 Ado receptor (NECA greater than Ado greater than R-PIA). Neuron-enriched cultures exhibited a maximum fourfold increase in cAMP in response to NECA; this was decreased a further eightfold when the cultures had prolonged exposure to the antimitotic agent, c-Ara, to eliminate greater than 98% of the nonneuronal cells. Low (nM) amounts of the Ado agonists inhibited cAMP formation in both cell types. In the astrocytes, the order of potency of inhibition of isoproterenol-stimulated cAMP formation was typical of an A1 receptor (R-PIA greater than Ado greater than NECA); maximum inhibition was 55-65%. Isoproterenol did not increase cAMP in the neuronal cultures. However, forskolin-stimulated formation was effectively (approximately 50%) inhibited by A1 Ado agonists; inhibition was not affected by prolonged treatment with c-Ara. From this study we tentatively concluded that rat astrocytes and neurons both contain inhibitory A1 Ado receptors, but that the stimulatory "A2" subtype is localized mainly on astrocytes.
在大鼠脑星形胶质细胞和神经元的原代培养物中，研究了腺苷（Ado）及其类似物对细胞内环磷酸腺苷（cAMP）形成的调节作用。在磷酸二酯酶抑制剂Ro 20 - 1724存在的情况下，两种细胞类型中cAMP的基础水平在40 - 120 pmol/mg蛋白质范围内。用腺苷脱氨酶处理细胞后，水平未发生改变，这表明在标准培养条件下它们不会产生大量内源性腺苷。在星形胶质细胞中，微摩尔量的激动剂可使cAMP增加至比基础值高30倍；相对效力是典型的A2腺苷受体（NECA大于Ado大于R - PIA）。富含神经元的培养物对NECA的反应中，cAMP最多增加四倍；当培养物长时间暴露于抗有丝分裂剂c - Ara以消除超过98%的非神经元细胞时，这种增加进一步降低了八倍。低（纳摩尔）量的腺苷激动剂在两种细胞类型中均抑制cAMP的形成。在星形胶质细胞中，抑制异丙肾上腺素刺激形成cAMP的效力顺序是典型的A1受体（R - PIA大于Ado大于NECA）；最大抑制率为55 - 65%。异丙肾上腺素在神经元培养物中不会增加cAMP。然而，毛喉素刺激的形成被A1腺苷激动剂有效抑制（约50%）；抑制不受c - Ara长时间处理的影响。从这项研究中，我们初步得出结论，大鼠星形胶质细胞和神经元都含有抑制性A1腺苷受体，但刺激性的“A2”亚型主要定位于星形胶质细胞。
