Interactions between H1-antagonists and opioids: a drug discrimination study

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Opioid and histamine H1-receptor antagonist combinations can enhance rewarding effects.
• Discriminative stimulus effects are believed to relate to drug rewarding properties.

Purpose of the Study:

• To examine the effects of combined opioid and H1-antagonist treatment on discriminative stimulus effects in rats.
• To investigate the relationship between drug combinations, discriminative stimuli, and rewarding effects.

Main Methods:

• Rats were trained to discriminate between cocaine or morphine and saline.
• The effects of opioids (pentazocine, dihydrocodeine) and H1-antagonists (tripelennamine, chlorpheniramine) alone and in combination were assessed.
• Generalization and potentiation of drug-specific discriminative stimulus effects were analyzed.

Main Results:

• H1-antagonists, but not opioids, generalized to cocaine's discriminative effects.
• Opioids potentiated the cocaine-like discriminative effects of H1-antagonists.
• Opioids, but not H1-antagonists, generalized to morphine's discriminative effects.
• H1-antagonists did not affect the morphine-like discriminative effects of opioids.

Conclusions:

• Opioid potentiation of H1-antagonist's cocaine-like discriminative effects may contribute to enhanced rewarding effects of these combinations.
• Findings suggest a specific interaction between opioids and H1-antagonists influencing drug reward pathways.