Genetic Background Underlying 5-HT_1A Receptor Functioning Affects the Response to Fluoxetine.

Area of Science:

• Neuroscience
• Pharmacology
• Genetics

Background:

• Genetic background influences drug sensitivity, a key factor in personalized medicine.
• Recombinant B6-M76C mice possess a specific chromosomal fragment affecting serotonin 5-HT1A receptor sensitivity and expression.
• These mice exhibit altered 5-HT1A receptor function compared to control B6-M76B mice.

Purpose of the Study:

• To investigate the impact of chronic fluoxetine treatment on the behavior and brain serotonin system of recombinant B6-M76C mice.
• To compare the effects of fluoxetine in B6-M76C mice with those in control B6-M76B mice.
• To explore the role of genetic background in antidepressant sensitivity and resistance.

Main Methods:

• Chronic administration of fluoxetine (20 mg/kg, 14 days, i.p.) to B6-M76B and B6-M76C mice.
• Behavioral assessment using the forced swim test.
• Analysis of serotonin 5-HT1A receptor mRNA and protein levels.
• Measurement of tryptophan hydroxylase-2 (TPH2) and serotonin transporter (SERT) gene and protein expression.
• Quantification of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in brain regions.

Main Results:

• Fluoxetine induced pro-depressive effects in B6-M76C mice, unlike B6-M76B mice.
• In B6-M76C mice, fluoxetine decreased 5-HT1A receptor mRNA and protein, and increased Freud-1 protein.
• Fluoxetine altered TPH2 and SERT expression and 5-HT/5-HIAA levels differently across brain regions in both mouse lines.

Conclusions:

• Genetic background variations significantly alter sensitivity to selective serotonin reuptake inhibitor (SSRI) antidepressants like fluoxetine.
• The study provides evidence for disrupted 5-HT1A autoreceptor functioning in B6-M76C mice.
• B6-M76C mice serve as a valuable model for studying antidepressant resistance.