Boutros N N, Uretsky N, Berntson G, Bornstein R
Department of Psychiatry, Ohio State University, Columbus.
Biol Psychiatry. 1994 Aug 15;36(4):242-8. doi: 10.1016/0006-3223(94)90606-8.
The purpose of this study was to determine the effect of cocaine on inhibitory sensory processing mechanisms in the brain. To accomplish this aim, recording electrodes were surgically placed into the vertex region of 12 rats. After recovery from surgery, rats were injected once daily for 5 days with either cocaine (20 mg/kg, IP) or saline. Immediately and 23 hr after each injection, the rats were tested for sensory gating mechanisms. They were presented with a series of two clicking sounds, a conditioning and testing click, delivered 0.5 sec apart, and the amplitude of the N40 responses to each of these clicks was recorded. The ratios of the amplitude of the N40 response to the testing click over that of the conditioning click (T/C ratio) were calculated for each animal for each testing period. The T/C ratios of the control (Saline-injected) animals were less than one, indicating that the conditioning stimulus was able to activate inhibitory neural pathways, producing a decrease in the response to the testing stimulus. The T/C ratios of the cocaine-treated animals were significantly greater than those of controls when the tests were conducted either immediately after injection or 23 hr later. These observations suggest that cocaine can impair mechanisms involved in the gating of responses to auditory stimuli. The higher T/C ratio found at 23 hr after cocaine injection suggests that an impairment in the gating mechanism may be produced by an arousal response that is associated with the environment in which the animals had been injected with cocaine.
本研究的目的是确定可卡因对大脑中抑制性感觉加工机制的影响。为实现这一目标，通过手术将记录电极植入12只大鼠的头顶区域。术后恢复后，大鼠连续5天每天接受一次注射，注射药物为可卡因（20mg/kg，腹腔注射）或生理盐水。每次注射后即刻和23小时后，对大鼠进行感觉门控机制测试。给它们呈现一系列两个点击声，一个条件点击声和一个测试点击声，两者间隔0.5秒，记录对每个点击声的N40反应的幅度。计算每个动物在每个测试时间段内，测试点击声的N40反应幅度与条件点击声的N40反应幅度之比（T/C比）。对照（注射生理盐水）动物的T/C比小于1，表明条件刺激能够激活抑制性神经通路，使对测试刺激的反应降低。在注射后即刻或23小时后进行测试时，可卡因处理动物的T/C比显著高于对照组。这些观察结果表明，可卡因会损害参与听觉刺激反应门控的机制。在注射可卡因23小时后发现的较高T/C比表明，门控机制的损害可能是由与动物注射可卡因时所处环境相关的觉醒反应所导致的。
