Johnson P I, Napier T C
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood IL 60153, USA.
Neuroscience. 1997 Mar;77(1):187-97. doi: 10.1016/s0306-4522(96)00482-4.
Microiontophoresis was used to investigate the influence of morphine on the GABA- and glutamate-evoked responses of ventral pallidal neurons recorded extracellularly from chloral hydrate-anesthetized rats. Of the GABA-sensitive neurons (50 of 69 tested) in the ventral pallidum, all displayed a decreased firing rate when GABA was applied, whereas all of the glutamate-sensitive neurons (29 of 40 tested) increased neuronal activity in the presence of glutamate. The majority of ventral pallidal cells tested (65 of 83) were sensitive to iontophoretically applied morphine, and both increases and decreases in neuronal activity were observed. The ability of morphine to alter the ratio between amino acid-evoked activity ("signal") and spontaneous firing ("noise") was used as an indicator of morphine modulation. A morphine subthreshold ejection current, i.e. one that did not change spontaneous firing rate, and a morphine ejection current that produced approximately 50% of the maximum opioid-induced neuronal response were chosen for this evaluation. When morphine was co-iontophoresed with GABA or glutamate, attenuation of the amino acid signal-to-noise ratio was generally seen, though some potentiations were observed. These changes were independent of the direction of morphine-induced changes in spontaneous firing rate. Both sub- and suprathreshold ejection currents were capable of affecting GABA- and glutamate-evoked responses. These data suggest that morphine is a robust ventral pallidal neuromodulator. As ventral pallidal amino acid activity is important in the integration of sensorimotor information, opioid modulation of amino acid transmission in the ventral pallidum may have a profound effect on this integration.
采用微量离子电泳法研究吗啡对水合氯醛麻醉大鼠腹侧苍白球神经元细胞外记录的γ-氨基丁酸（GABA）和谷氨酸诱发反应的影响。在腹侧苍白球的GABA敏感神经元（69个测试中有50个）中，施加GABA时所有神经元的放电频率均降低，而在谷氨酸敏感神经元（40个测试中有29个）中，存在谷氨酸时神经元活动增加。大多数测试的腹侧苍白球细胞（83个中有65个）对微量离子电泳施加的吗啡敏感，观察到神经元活动既有增加也有减少。吗啡改变氨基酸诱发活动（“信号”）与自发放电（“噪声”）之间比率的能力被用作吗啡调节的指标。为此评估选择了一个吗啡阈下喷射电流，即一个不会改变自发放电频率的电流，以及一个产生约50%最大阿片类药物诱导神经元反应的吗啡喷射电流。当吗啡与GABA或谷氨酸共同进行离子电泳时，通常会观察到氨基酸信噪比的衰减，尽管也观察到了一些增强作用。这些变化与吗啡诱导的自发放电频率变化方向无关。阈下和阈上喷射电流均能够影响GABA和谷氨酸诱发的反应。这些数据表明吗啡是一种强大的腹侧苍白球神经调节剂。由于腹侧苍白球氨基酸活动在感觉运动信息整合中很重要，阿片类药物对腹侧苍白球氨基酸传递的调节可能对这种整合有深远影响。
