Zhang S Y, Zhang Y P, Zhang M L, Qi H X, Wang B
Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing.
Sheng Li Xue Bao. 1992 Oct;44(5):448-54.
Female Wistar rats were trained in a Skinner-box, 30 trials per day in a dark room to establish operant defence conditioning. Training started with a light (15 s), then combined with footshock for further 8 s. When the rats learned to press the key to avoid footshock within 15 s, conditioned response was considered established. After the rats reached a conditioning rate (CR) above 80% for 5 days, cannulae were implanted into caudate-putamen. Two to three days later, Met-enkephalin (MEK) or bestatin (an aminopeptidase inhibitor) was injected bilaterally into caudate-putamen. 30 min, 2 h, 24 h and 48 h after injection, conditioning tests were conducted, with each session consisting of 30 trials. Control experiments were done when 0.9% NaCl (NS) was injected. After injection of NS, CR maintained above 80% in all 4 test sessions. MEK (60 ng/rat) or bestatin (10 micrograms/rat) significantly lowered the CR during the 30 min and 2 h test session. In the latter case, the latency (L) was also prolonged. However both CR and L returned to the control level in the 24 h and 48 h test sessions. Naloxone (2 mg/kg, i.p.) blocked the conditioning-depression effect of bestatin. No significant alteration was seen in locomotor activity after MEK or bestatin injection. The results suggest that enkephalin in caudate-putamen may be involved in the regulation of retrieval of conditioning. Bestatin mimics the effect of MEK on conditioning reflex probably by increasing production of endogenous enkephalin.
将雌性Wistar大鼠置于斯金纳箱中进行训练，每天在暗室中进行30次试验，以建立操作性防御条件反射。训练开始时给予15秒的光照，然后再结合8秒的足部电击。当大鼠学会在15秒内按压按键以避免足部电击时，即认为条件反应已建立。当大鼠连续5天达到80%以上的条件反射率（CR）后，将套管植入尾状核-壳核。两到三天后，将甲硫氨酸脑啡肽（MEK）或贝司他汀（一种氨肽酶抑制剂）双侧注射到尾状核-壳核中。注射后30分钟、2小时、24小时和48小时进行条件反射测试，每次测试包括30次试验。当注射0.9%氯化钠（NS）时进行对照实验。注射NS后，在所有4次测试中CR均维持在80%以上。MEK（60纳克/只大鼠）或贝司他汀（10微克/只大鼠）在30分钟和2小时的测试中显著降低了CR。在后一种情况下，潜伏期（L）也延长了。然而，在24小时和48小时的测试中，CR和L均恢复到对照水平。纳洛酮（2毫克/千克，腹腔注射）可阻断贝司他汀的条件反射抑制作用。注射MEK或贝司他汀后，运动活动未见明显改变。结果表明，尾状核-壳核中的脑啡肽可能参与条件反射恢复的调节。贝司他汀可能通过增加内源性脑啡肽的产生来模拟MEK对条件反射的作用。
