Siegel S
Science. 1976 Jul 23;193(4250):323-5. doi: 10.1126/science.935870.
Rats were made tolerant to morphine in either of two environments and then assessed for morphine-induced alteration of pain sensitivity in both environments. Analgesic tolerance was displayed when rats were tested in that environment in which they previously received morphine, but not in the alternative environment. The results indicate than an association between environmental cues and the systemic effects of morphine is crucial to tolerance development.
大鼠在两种环境中的任意一种中产生对吗啡的耐受性，然后在这两种环境中评估吗啡引起的疼痛敏感性变化。当在先前接受过吗啡的环境中对大鼠进行测试时，会表现出镇痛耐受性，但在另一种环境中则不会。结果表明，环境线索与吗啡的全身效应之间的关联对于耐受性的形成至关重要。
