Effects of Chronic Fluoxetine Treatment on Catalepsy and the Immune Response in Mice with a Genetic Predisposition to Freezing Reactions: The Roles of Types 1A and 2A Serotonin Receptors and the tph2 and SERT Genes.

ASC (Antidepressant-Sensitive Catalepsy) mice, bred for a high predisposition to catalepsy, are characterized by depression-like behavior and decreased immune responses. Chronic administration of fluoxetine, which is a selective serotonin reuptake inhibitor antidepressant widely used in clinical practice, to mice of this strain weakened catalepsy and normalized the number of rosette-forming cells in the spleen. In mice of the parental cataleptic strain CBA/Lac, fluoxetine had no effect on the level of catalepsy or the immune response. Analysis of the effects of fluoxetine on the functional activity of 5-HT_1A and 5-HT_2A receptors, and the expression of 5-HT_1A receptor genes in the frontal cortex and midbrain and 5-HT_2A receptors in the frontal cortex, as well as the tryptophan hydroxylase-2 and the serotonin transporter genes in the midbrain showed that the antidepressant had no effect on these parameters in ASC mice, but decreased the functional activity of 5-HT_2A receptors in CBA/Lac mice. The possibility that the actions of fluoxetine on catalepsy and the immune response in mice with depression-like states are mediated via other serotoninergic mechanisms is discussed. [ABSTRACT FROM AUTHOR]