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Recall rendered dependent on an opiate state
L A Bruins Slot1, F C Colpaert
1Centre de Recherche Pierre Fabre, Castres, France.
Abstract:
Remembering may require that the organism be in a state that is similar to that in which the event was initially experienced (state dependence [StD]). We determined whether morphine induces StD and whether this StD is conceivably involved in the analgesic effects that opiates produce. Rats trained while treated with morphine recalled the learned response when tested with this opiate but not when in their nondrugged state, and vice versa. Furthermore, morphine analgesia occurred in a manner that was similar to StD in terms of both dose and time. In as much as responses to nociceptive stimulation are learned during the course of ontogeny, StD may constitute the psychophysiological mechanism whereby opiates produce their characteristic analgesic effects.
Insights
Morphine induces state dependence (StD), where learning is recalled only in the drug state present during training. This StD mechanism may explain how opiates produce their analgesic effects.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Psychology
Background:
- State dependence (StD) suggests memory recall is optimal in the same physiological state as learning.
- Opiates, like morphine, are known for their analgesic properties.
Purpose of the Study:
- To investigate if morphine induces state dependence in rats.
- To determine if morphine-induced state dependence contributes to opiate analgesia.
Main Methods:
- Rats were trained on a learned response under morphine or in a nondrugged state.
- Recall of the learned response was tested in both drugged and nondrugged states.
- Morphine analgesia was assessed in relation to dose and time.
Main Results:
- Rats trained with morphine recalled the response only when tested with morphine, not when drug-free.
- Rats trained drug-free recalled the response only when tested drug-free, not with morphine.
- The dose-response and time course of morphine analgesia mirrored that of state dependence.
Conclusions:
- Morphine reliably induces state dependence in rats.
- State dependence may be the psychophysiological mechanism underlying opiate analgesia.
- This finding has implications for understanding how opiates affect learned responses to pain.