The ventral tegmental area (VTA) plays an important role in the reward and motivational processes that facilitate the development of drug addiction. Presynaptic α1-AR activation modulates glutamate and Gamma-aminobutyric acid (GABA) release. This work elucidates the role of VTA presynaptic α1-ARs and their modulation on glutamatergic and GABAergic neurotransmission during cocaine sensitization. Excitatory and inhibitory currents (EPSCs and IPSCs) measured by a whole cell voltage clamp show that α1-ARs activation increases EPSCs amplitude after 1 day of cocaine treatment but not after 5 days of cocaine injections. The absence of a pharmacological response to an α1-ARs agonist highlights the desensitization of the receptor after repeated cocaine administration. The desensitization of α1-ARs persists after a 7-day withdrawal period. In contrast, the modulation of α1-ARs on GABA neurotransmission, shown by decreases in IPSCs' amplitude, is not affected by acute or chronic cocaine injections. Taken together, these data suggest that α1-ARs may enhance DA neuronal excitability after repeated cocaine administration through the reduction of GABA inhibition onto VTA dopamine (DA) neurons even in the absence of α1-ARs' function on glutamate release and protein kinase C (PKC) activation. α1-AR modulatory changes in cocaine sensitization increase our knowledge of the role of the noradrenergic system in cocaine addiction and may provide possible avenues for therapeutics.

译文

:腹侧被盖区(VTA)在促进药物成瘾的奖励和动机过程中起着重要作用。突触前的α1-AR活化调节谷氨酸和γ-氨基丁酸(GABA)的释放。这项工作阐明了可卡因致敏过程中VTA突触前α1-ARs的作用及其对谷氨酸能和GABA能神经传递的调节作用。通过全细胞电压钳测量的兴奋性和抑制性电流(EPSC和IPSC)显示,可卡因治疗1天后注射α1-ARs激活会增加EPSCs幅度,但注射可卡因5天后却不会。对α1-ARs激动剂的药理反应不存在突出了重复可卡因给药后受体的脱敏作用。停药7天后,α1-ARs的脱敏仍然持续。相反,急性或慢性可卡因注射并未影响IPSCs振幅降低所显示的GABA神经传递中α1-ARs的调节。综上所述,这些数据表明,即使在缺乏α1-ARs谷氨酸释放和蛋白激酶C功能的情况下,重复可卡因给药后,α1-ARs仍可通过减少VTA多巴胺(DA)神经元的GABA抑制作用来增强DA神经元的兴奋性( PKC)激活。可卡因敏化中的α1-AR调节性变化增加了我们对去甲肾上腺素能系统在可卡因成瘾中的作用的了解,并可能为治疗提供可能的途径。

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