Miller D K, Crooks P A, Dwoskin L P
College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA.
Neuropharmacology. 2000 Oct;39(13):2654-62. doi: 10.1016/s0028-3908(00)00140-4.
The present study evaluated the interaction of lobeline with neuronal nicotinic acetylcholine receptors using two in vitro assays, [(3)H] overflow from [(3)H]dopamine ([(3)H]DA)-preloaded rat striatal slices and (86)Rb(+) efflux from rat thalamic synaptosomes. To assess agonist interactions, the effect of lobeline was determined and compared to S(-)-nicotine. To assess antagonist interactions, the ability of lobeline to inhibit the effect of S(-)-nicotine was determined. Both S(-)-nicotine (0.1-1 microM) and lobeline (>1.0 microM) evoked [(3)H] overflow from superfused [(3)H]DA-preloaded striatal slices. However, lobeline-evoked [(3)H] overflow is mecamylamine-insensitive, indicating that this response is not mediated by nicotinic receptors. Moreover, at concentrations (<1.0 microM) which did not evoke [(3)H] overflow, lobeline inhibited S(-)-nicotine (0.1-10 microM)-evoked [(3)H] overflow, shifting the S(-)-nicotine concentration-response curve to the right. S(-)-Nicotine (30 nM-300 microM) increased (EC(50) value=0.2 microM) (86)Rb(+) efflux from thalamic synaptosomes. In contrast, lobeline (1 nM-10 microM) did not evoke (86)Rb(+) efflux, and the lack of intrinsic activity indicates that lobeline is not an agonist at this nicotinic receptor subtype. Lobeline completely inhibited (IC(50) value=0.7 microM) (86)Rb(+) efflux evoked by 1 microM S(-)-nicotine, a concentration which maximally stimulated (86)Rb(+) efflux. Thus, the results of these in vitro experiments demonstrate that lobeline inhibits the effects of S(-)-nicotine, and suggest that lobeline acts as a nicotinic receptor antagonist.
本研究使用两种体外试验评估了洛贝林与神经元烟碱型乙酰胆碱受体的相互作用，即来自[³H]多巴胺（[³H]DA）预加载大鼠纹状体切片的[³H]溢出以及大鼠丘脑突触体的⁸⁶Rb⁺外流。为了评估激动剂相互作用，测定了洛贝林的作用并与S(-)-尼古丁进行比较。为了评估拮抗剂相互作用，测定了洛贝林抑制S(-)-尼古丁作用的能力。S(-)-尼古丁（0.1 - 1微摩尔）和洛贝林（>1.0微摩尔）均能引起来自经超融合的[³H]DA预加载纹状体切片的[³H]溢出。然而，洛贝林引起的[³H]溢出对美加明不敏感，表明该反应不是由烟碱受体介导的。此外，在未引起[³H]溢出的浓度（<1.0微摩尔）下，洛贝林抑制S(-)-尼古丁（0.1 - 10微摩尔）引起的[³H]溢出，使S(-)-尼古丁浓度 - 反应曲线右移。S(-)-尼古丁（30纳摩尔 - 300微摩尔）增加了（半数有效浓度（EC₅₀）值 = 0.2微摩尔）丘脑突触体的⁸⁶Rb⁺外流。相比之下，洛贝林（1纳摩尔 - 10微摩尔）未引起⁸⁶Rb⁺外流，且缺乏内在活性表明洛贝林不是该烟碱受体亚型的激动剂。洛贝林完全抑制了（半数抑制浓度（IC₅₀）值 = 0.7微摩尔）由1微摩尔S(-)-尼古丁引起的⁸⁶Rb⁺外流，该浓度能最大程度地刺激⁸⁶Rb⁺外流。因此，这些体外实验结果表明洛贝林抑制S(-)-尼古丁的作用，并提示洛贝林作为烟碱受体拮抗剂发挥作用。
