The Dopamine D5 Receptor Is Involved in Working Memory.

Area of Science:

• Neuroscience
• Cognitive Science
• Molecular Biology

Background:

• Dopamine D1-like receptors (D1 and D5) are implicated in cognitive functions.
• Lack of selective ligands for D1 and D5 receptors hinders understanding of their distinct roles.

Purpose of the Study:

• To elucidate the specific role of the dopamine D5 receptor in higher-order cognitive functions using D5 receptor knockout mice.
• To identify the molecular mechanisms underlying D5 receptor function in the prefrontal cortex.

Main Methods:

• Utilized D5 receptor homozygous (-/-) and heterozygous (+/-) knockout mouse models.
• Assessed cognitive functions including spatial working memory (T-maze task) and temporal order memory (object recognition task).
• Analyzed molecular biomarkers of dopaminergic function in the prefrontal cortex (PFC), including Akt phosphorylation and CaMKKbeta levels.

Main Results:

• D5 knockout mice exhibited impaired performance in tasks with higher working memory demands.
• Significant memory deficits were observed in D5 knockout mice in a temporal order object recognition task.
• No significant differences in locomotor activity or object exploration were found between genotypes.
• A gene-dose effect on Akt phosphorylation at Ser473 was observed in the PFC, with increased levels in D5 knockout mice.
• A trend towards reduced CaMKKbeta levels was noted in D5 knockout mice.

Conclusions:

• Dopamine D5 receptors play a novel and critical role in regulating spatial working memory and temporal order memory.
• Molecular changes in Akt phosphorylation and CaMKKbeta in the PFC are associated with D5 receptor function in memory processes.
• These findings provide new insights into the specific contributions of D5 receptors to cognitive function.