Kehne J H, Davis M
Behav Neurosci. 1984 Dec;98(6):955-68. doi: 10.1037//0735-7044.98.6.955.
Theories of habituation have included an increase in postsynaptic inhibition as one possible mechanism underlying response decrement following repetitive stimulus presentation. In this study, the glycine antagonist strychnine (1.0 mg/kg, ip, 10 min pretreatment) was used to investigate the involvement of glycinergic neurons in the development and/or expression of short-term (within-session) habituation (Experiment 1) and long-term (between-sessions) habituation (Experiments 2 and 3) of the acoustic startle response in rats. Over a range of eliciting-stimulus intensities (95, 105, and 115 dB) and interstimulus intervals (3, 7, 13, and 27 s), strychnine markedly increased startle amplitude, relative to water injection, whereas it failed to attenuate the rate of within-session habituation (Experiment 1). In Experiment 2, rats that were exposed to daily sessions of startle-eliciting stimuli for 4 days and then tested on the fifth day showed lower overall levels of startle amplitude, relative to rats that had not received prior habituation training. Strychnine injected prior to the test session again increased startle amplitude but did not block the expression of between-sessions habituation. In Experiment 3, rats that were injected with either strychnine or water prior to each of three daily habituation training sessions and subsequently tested on Day 4 showed similar between-sessions habituation, relative to untrained rats that had received daily injections in the animal room. In summary, strychnine increased startle amplitude without affecting either within-session or between-sessions habituation of acoustic startle. These results emphasize the need to discern between drug effects on response amplitude per se and effects on response habituation. Furthermore, the data indicate that a buildup of inhibition in glycinergic neurons does not explain either within-session or between-sessions habituation of acoustic startle in rats. These results are discussed in light of current theories of habituation.
习惯化理论认为，突触后抑制增强是重复刺激呈现后反应减弱的一种可能机制。在本研究中，使用甘氨酸拮抗剂士的宁（1.0毫克/千克，腹腔注射，预处理10分钟）来研究甘氨酸能神经元在大鼠听觉惊跳反应的短期（实验过程中）习惯化（实验1）和长期（实验过程间）习惯化（实验2和3）的形成和/或表达中的作用。在一系列引发刺激强度（95、105和115分贝）和刺激间隔（3、7、13和27秒）下，与注射水相比，士的宁显著增加了惊跳幅度，而它未能减弱实验过程中的习惯化速率（实验1）。在实验2中，与未接受过习惯化训练的大鼠相比，每天接受4天惊跳引发刺激并在第5天进行测试的大鼠的惊跳幅度总体水平较低。在测试前注射士的宁再次增加了惊跳幅度，但并未阻断实验过程间习惯化的表达。在实验3中，在每天的三次习惯化训练前分别注射士的宁或水并随后在第4天进行测试的大鼠，与在动物房每天接受注射的未训练大鼠相比，表现出相似的实验过程间习惯化。总之，士的宁增加了惊跳幅度，而不影响听觉惊跳的实验过程内或实验过程间习惯化。这些结果强调了区分药物对反应幅度本身的影响和对反应习惯化的影响的必要性。此外，数据表明甘氨酸能神经元中抑制的积累并不能解释大鼠听觉惊跳的实验过程内或实验过程间习惯化。根据当前的习惯化理论对这些结果进行了讨论。
