Long-term haloperidol elevates dopamine D4 receptors by 2-fold in rats

Area of Science:

• Neuropharmacology
• Molecular Psychiatry

Background:

• Neuroleptic medications are known to increase dopamine D2-like receptors with chronic use.
• The specific impact of neuroleptics on the dopamine D4 receptor subtype remains less understood.

Purpose of the Study:

• To investigate the effect of chronic haloperidol administration on dopamine D4 receptor mRNA and protein levels in the rat striatum.
• To quantify changes in dopamine D4 receptor density in response to neuroleptic treatment.

Main Methods:

• Rats were treated with haloperidol for one month.
• Dopamine D4 receptor mRNA was quantified using reverse transcription and amplification due to low endogenous levels.
• Dopamine D4 receptor density was indirectly measured by Scatchard analysis of [3H]nemonapride and [3H]raclopride binding.

Main Results:

• Haloperidol treatment resulted in an approximate 2-fold increase in dopamine D4 receptor density in the rat striatum.
• Dopamine D4 receptor mRNA levels also showed an approximate 2-fold increase.
• Dopamine D2 and D3 receptors combined showed a 19% increase in density.

Conclusions:

• Chronic haloperidol treatment upregulates both the protein and mRNA levels of dopamine D4 receptors in the rat striatum.
• This suggests that dopamine D4 receptors are sensitive to neuroleptic-induced changes, similar to other D2-like receptors.