Golombek D A, Chuluyan H E, Kanterewicz B I, Cardinali D P
Departmento de Fisiologia, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
J Neural Transm Gen Sect. 1994;98(3):237-46. doi: 10.1007/BF01276539.
The objective of this study was to assess whether rat pineal melatonin content could be modified in a classical conditioning paradigm. In rats kept under light (200 lux) from 06.00 to 18.00 h daily, the time of lights off was selected as the unconditioned stimulus (US). Restricted water availability (from 10 min before to 10 min after light-dark, LD, transition) was the conditioned stimulus (CS). The conditioned and unconditioned responses were measured as the changes in pineal melatonin levels 4 h after LD transition. In animals under regular lighting conditions, lights out at 18.00 h (the US) caused a 4.4-7.8-fold increase of pineal melatonin concentration 4 h after later, when compared to animals maintained under light for the 4 h-period. After a training period of 7 days of restricted water availability (the CS), significantly augmented pineal melatonin levels were found in rats that were exposed to water but were maintained under light for the 4 h period after expected LD transition. The control animals for this experiment, i.e., rats which had undergone the training period, were kept for 4 h under light after expected LD transition, and did not receive water at LD transition, exhibited very low pineal melatonin levels. The conditioned increase of pineal melatonin content attained lower values than those in rats exposed to normal lighting conditions. It also fulfilled the contingency criterion, that is, it caused at trial a significant elevation of pineal melatonin content only when water availability was applied from 10 min previously to LD transition during training, and not 20 min after LD transition. After a training period of 7 days, restricted water availability applied 4 h before lights off (at 14.00 h), caused an enhanced production of melatonin 4 h later, regardless of the animals being exposed either to a dark or to a light environment. The results indicate that pineal melatonin production can be manipulated in a classical conditioning paradigm, when an appropriate CS stimulus is used.
本研究的目的是评估在经典条件反射范式下大鼠松果体褪黑素含量是否会发生改变。在每天06:00至18:00处于光照（200勒克斯）下的大鼠中，选择熄灯时间作为非条件刺激（US）。限制水的供应（从明暗交替前10分钟到明暗交替后10分钟）作为条件刺激（CS）。条件反应和非条件反应通过明暗交替后4小时松果体褪黑素水平的变化来衡量。在正常光照条件下的动物中，18:00熄灯（非条件刺激）会导致4小时后松果体褪黑素浓度比在光照下维持4小时的动物增加4.4至7.8倍。经过7天限制水供应（条件刺激）的训练期后，在预期的明暗交替后暴露于水但在光照下维持4小时的大鼠中，发现松果体褪黑素水平显著升高。该实验的对照动物，即经过训练期的大鼠，在预期的明暗交替后在光照下保持4小时，且在明暗交替时不给予水，其松果体褪黑素水平非常低。松果体褪黑素含量的条件性增加达到的值低于暴露于正常光照条件下的大鼠。它也符合偶联标准，即仅在训练期间从明暗交替前10分钟应用水供应时，而非在明暗交替后20分钟，才会在试验中导致松果体褪黑素含量显著升高。经过7天的训练期后，在熄灯前4小时（14:00）应用限制水供应，无论动物处于黑暗还是光照环境，4小时后都会导致褪黑素分泌增加。结果表明，当使用适当的条件刺激时，松果体褪黑素的分泌可以在经典条件反射范式中被调控。
