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The ambulation-increasing effect of buprenorphine in mice: comparison with the effect of morphine
1Division for Behavior Analysis, Gunma University School of Medicine.
Abstract:
Effects of buprenorphine on ambulatory activity in mice were studied, and the result s were compared with those of morphine. Buprenorphine, at 0.01-3 mg/kg s.c., increased the mouse's ambulatory activity in a dose-dependent manner with Straub tail-reaction. The effect reached to the maximum level at 10-20 min and persisted for 2-3 hr after the administration. The overall activity counts for 3 hr were almost identical when 1 mg/kg of buprenorphine and 10 mg/kg of morphine were administered. Naloxone, 0.01-1 mg/kg s.c., reduced the ambulation-increasing effect of both buprenorphine and morphine, but the reducing-action of naloxone was stronger for morphine than for buprenorphine. However, the combined administration of buprenorphine and morphine demonstrated no significant modification in individual drug effects. On the other hand, the ambulation-increasing effect of buprenorphine and morphine were enhanced by combined s.c. administration of methamphetamine (1 mg/kg), cocaine (10 mg/kg), scopolamine (0.5 mg/kg), or caffeine (10 mg/kg). Such enhancing effects of methamphetamine and cocaine were much greater for buprenorphine than for morphine. In contrast, haloperidol (0.05 mg/kg), pilocarpine (2 mg/kg), and N6-(L-2-phenylisopropyl)-adenosine (0.1 mg/kg) reduced the ambulation-increasing effect of buprenorphine or morphine. The modification by pilocarpine was more marked for morphine than for buprenorphine. The present results indicate that buprenorphine and morphine possess differential effectiveness on dopaminergic and/or cholinergic systems.
Insights
Buprenorphine and morphine increase mouse ambulatory activity, with naloxone reducing this effect. Other drugs differentially modulated these opioid-induced behaviors, suggesting distinct dopaminergic and cholinergic system interactions.
Area of Science:
- Pharmacology
- Neuroscience
Background:
- Opioid analgesics like morphine and buprenorphine are widely used.
- Understanding their effects on motor activity is crucial for clinical application and mechanism elucidation.
Purpose of the Study:
- To compare the effects of buprenorphine and morphine on ambulatory activity in mice.
- To investigate the influence of various neurochemical agents on these opioid-induced behavioral changes.
Main Methods:
- Subcutaneous administration of buprenorphine and morphine to mice.
- Dose-response assessment of ambulatory activity.
- Co-administration with antagonists (naloxone) and other drugs (methamphetamine, cocaine, scopolamine, caffeine, haloperidol, pilocarpine, adenosine derivatives).
Main Results:
- Buprenorphine, like morphine, dose-dependently increased ambulatory activity.
- Naloxone attenuated the effects of both opioids, more so for morphine.
- Co-administration with stimulants (methamphetamine, cocaine, etc.) enhanced opioid effects, with greater enhancement for buprenorphine by stimulants.
- Dopaminergic and cholinergic agents differentially modulated buprenorphine and morphine activity.
Conclusions:
- Buprenorphine and morphine exhibit distinct interactions with dopaminergic and/or cholinergic systems.
- These findings highlight differential neurochemical underpinnings of their behavioral effects.