Adaptive changes in behavior after repeated administration of various psychoactive drugs

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Drug conditioning can alter behavioral responses.
• Amphetamines and hallucinogens affect operant behavior.
• Serotonergic pathways are implicated in drug-induced behavioral changes.

Purpose of the Study:

• Investigate the role of conditioning in d-amphetamine's effects on behavior.
• Characterize the behavioral effects of hallucinogenic drugs and their interactions.
• Examine the involvement of serotonergic mechanisms in drug-induced behavioral pauses.

Main Methods:

• Rats were exposed to d-amphetamine during locomotor activity and operant conditioning (FR-5).
• Continuous avoidance procedures were used to assess d-amphetamine's effects on response rates.
• Hallucinogenic drugs (LSD, mescaline, psilocybin, DOM, DMT) and d-amphetamine were tested in FR-5 paradigms.
• Tolerance and cross-tolerance to drug effects were examined.
• The effects of cinanserin, a serotonergic antagonist, were evaluated.

Main Results:

• Conditioning enhanced d-amphetamine-stimulated locomotor activity, persisting after drug withdrawal.
• d-Amphetamine decreased FR-5 response rates; tolerance varied with prior experience.
• Hallucinogenic drugs induced a characteristic pause in FR-5 responding, unlike d-amphetamine or chlorpromazine.
• Tolerance and cross-tolerance patterns among hallucinogens suggested common but not identical mechanisms.
• Cinanserin reversed the hallucinogen-induced pause in FR-5 responding.

Conclusions:

• Behavioral conditioning can lead to persistent alterations in drug response.
• Hallucinogenic drugs share common mechanisms of action, possibly involving serotonergic pathways.
• Serotonergic antagonism can reverse specific drug-induced behavioral effects.