Related Experiment Videos
No psychological dependence after oral administration of morphine to rats
1Institut für Pharmakologie und Toxikologie Universität des Saarlandes, Homburg/Saar FRG.
Abstract:
Rats subjected to forced oral self-administration of morphine solutions without or in combination with two daily i.p. injections of morphine preferred drinking water when this was offered in addition to morphine solutions. The daily intake of morphine during the terminal phase of self-administration of morphine was 50-80 mg/kg (oral application alone) or 270 mg/kg (oral and i.p. application). Morphine treated animals showed withdrawal symptoms on administration of naloxone 1 mg/kg i.p. during the period of self-administration, but not when they had started drinking exclusively water. The tail-flick test revealed no tolerance during prolonged treatment with morphine. The results indicate that no psychological dependence developed when morphine was applied orally and regularly.
Insights
Rats preferred water over morphine when offered, indicating no psychological dependence developed from oral morphine self-administration. This suggests oral morphine intake may not lead to addiction in this model.
Area of Science:
- Pharmacology
- Neuroscience
- Addiction Research
Background:
- Opioid self-administration is a key model for studying drug dependence.
- Understanding the route of administration's impact on dependence is crucial for addiction research.
Purpose of the Study:
- To investigate the development of psychological dependence in rats during forced oral self-administration of morphine.
- To assess the role of administration route (oral vs. oral+IP) in morphine dependence.
Main Methods:
- Rats underwent forced oral self-administration of morphine solutions.
- Morphine intake was measured, with some groups receiving additional intraperitoneal (IP) injections.
- Naloxone challenge and tail-flick tests were used to assess withdrawal symptoms and tolerance.
Main Results:
- Rats preferred drinking water over morphine solutions when both were available.
- High daily morphine intake was observed (50-80 mg/kg oral alone, 270 mg/kg oral+IP).
- Withdrawal symptoms occurred with naloxone during self-administration but not after switching to water; no tolerance developed.
Conclusions:
- Forced oral self-administration of morphine in rats did not lead to psychological dependence.
- The route of administration and availability of alternative non-drug rewards (water) may prevent the development of dependence.
- Oral morphine administration, even at high doses, may not induce addiction-like behaviors in this experimental setup.