Supersensitivity to dopaminergic agonists induced by haloperidol

Area of Science:

• Neuropharmacology
• Behavioral Neuroscience
• Psychopharmacology

Background:

• Neuroleptic medications like haloperidol are used to treat psychosis by blocking dopamine receptors.
• Understanding the long-term effects of dopamine receptor blockade is crucial for managing treatment side effects.

Purpose of the Study:

• To investigate the behavioral consequences of chronic haloperidol and pimozide administration in mice.
• To examine the development and characteristics of withdrawal hyperactivity following neuroleptic treatment.
• To explore the role of dopamine receptor sensitivity in neuroleptic-induced behavioral changes.

Main Methods:

• Mice were fed diets containing haloperidol or pimozide for varying durations (1-11 days).
• Locomotor activity was measured before, during, and after drug withdrawal.
• Dose-response curves for dopaminergic agonists (apomorphine, piribedil, L-DOPA, d-amphetamine) were assessed during withdrawal.

Main Results:

• Chronic haloperidol and pimozide reduced locomotor activity; drug removal induced significant withdrawal hyperactivity.
• Withdrawal hyperactivity was maximal after 6 days of haloperidol treatment and persisted for several days.
• Dopaminergic agonists showed enhanced effects (motor activity, rearing, gnawing) during withdrawal, indicating increased receptor sensitivity.

Conclusions:

• Prolonged blockade of central dopamine receptors by neuroleptics can lead to adaptive changes, such as enhanced receptor sensitivity.
• This enhanced sensitivity likely underlies the observed withdrawal hyperactivity and altered behavioral responses to dopaminergic agonists.
• The findings support the hypothesis that neuroleptic treatment induces receptor supersensitivity, contributing to behavioral withdrawal symptoms.