Abstract
The present study was undertaken to investigate the hypothesis that the μ-opioid receptors play a crucial role in locomotor activity and sensitization to cocaine and morphine in wild-type and μ-opioid receptor knockout mice. Our results show that morphine and cocaine increased locomotor activity in wild-type mice, but failed to increase locomotor activity in μ-opioid receptor knockout mice, suggesting a contribution of μ-opioid receptor. Repeated morphine treatment induced sensitization in wild-type mice, but this was not observed in μ-opioid receptor knockout mice. In contrast repeated cocaine treatment produced sensitization in μ-opioid receptor knockout mice, but not in wild-type mice on day 6. However, the sensitization to cocaine was observed in μ-opioid receptor knockout and wild-type mice on day 12. These results suggest that the expression of μ-opioid receptor may contribute to locomotor sensitization induced by morphine, but that μ-opioid receptor does not play an important role in mediating sensitization to cocaine.
| Original language | English |
|---|---|
| Pages (from-to) | 37-40 |
| Number of pages | 4 |
| Journal | Neuroscience Letters |
| Volume | 344 |
| Issue number | 1 |
| DOIs | |
| State | Published - 19 Jun 2003 |
Keywords
- Behavioral sensitization
- Cocaine
- Knockout mice
- Locomotor activity
- Morphine
- μ-Opioid receptors
