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Functional alteration of opioid receptor subtypes in the mice exhibited conditioned suppression in motility
Abstract:
Mice exhibit a marked suppression of motility (conditioned suppression) when placed in the same environment in which they had previously received the electric footshock. The present study was designed to investigate the functional change of opioid receptor subtypes in the conditioned suppression group using an opioid binding assay technique. In the synaptic membrane of the conditioned suppression group, the binding capacities of [3H]naloxone at high and low affinity binding sites and of [3H]phencyclidine at high affinity binding site were significantly increased compared to those of the control group. On the other hand, the binding capacity of [3H]ethylketocyclazocine at both affinity binding sites in the conditioned suppression group was not changed. These results suggest that the binding function of different opioid receptor subtypes may be altered differently by stress.
Insights
Stress significantly alters opioid receptor binding in mice. Specifically, conditioned suppression due to footshock increases binding at certain opioid receptor subtypes, suggesting stress-induced functional changes in the opioid system.
Area of Science:
- Neuroscience
- Behavioral Science
- Pharmacology
Background:
- Mice display conditioned suppression, a decrease in motility, after experiencing footshock in a specific environment.
- The role of opioid receptor subtypes in stress-induced behavioral changes requires further investigation.
Purpose of the Study:
- To examine functional alterations in opioid receptor subtypes within the synaptic membranes of mice exhibiting conditioned suppression.
- To elucidate the impact of stress on the binding capacities of different opioid receptor subtypes.
Main Methods:
- Utilized an opioid binding assay technique to quantify receptor binding capacities.
- Compared binding affinities of [3H]naloxone, [3H]phencyclidine, and [3H]ethylketocyclazocine in conditioned suppression versus control groups.
Main Results:
- Significantly increased binding capacities for [3H]naloxone (high and low affinity) and [3H]phencyclidine (high affinity) were observed in the conditioned suppression group.
- No significant changes in binding capacity were found for [3H]ethylketocyclazocine at either affinity site in the conditioned suppression group.
Conclusions:
- Stress associated with conditioned suppression leads to differential functional changes in opioid receptor subtypes.
- These findings suggest that specific opioid receptor subtypes, like those binding naloxone and phencyclidine, are modulated by stress, while others, like those binding ethylketocyclazocine, may be less affected.