Behavioral evidence for dopamine receptor subsensitivity following chronic haloperidol

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Chronic neuroleptic administration clinically mimics a delayed onset of action.
• Understanding the neurochemical underpinnings of this delay is crucial for optimizing treatment.

Purpose of the Study:

• To investigate neurochemical mechanisms behind the delayed onset of behavioral suppression induced by chronic haloperidol.
• To examine dopamine autoreceptor sensitivity and postsynaptic adaptations following subthreshold haloperidol treatment.

Main Methods:

• Rats received chronic haloperidol (0.1 mg/kg) for 21 days.
• Apomorphine (low dose) was administered post-withdrawal to assess neurochemical responses.
• Behavioral suppression and yawning were measured as indicators of dopaminergic activity.

Main Results:

• Haloperidol treatment did not induce dopamine autoreceptor supersensitivity or postsynaptic supersensitivity.
• Rats treated with haloperidol showed reduced sensitivity to apomorphine-induced yawning.
• Metabolic changes were comparable between haloperidol and vehicle groups, indicating subthreshold effects.

Conclusions:

• Therapeutic doses of neuroleptics induce complex pre- and postsynaptic neuroadaptive changes.
• These adaptations involve both up- and down-regulation of dopaminergic systems.
• The mechanisms underlying the delayed onset of neuroleptic action are multifaceted.