Evaluation of 5-HT 7 receptor antagonism for the treatment of anxiety, depression, and schizophrenia through the use of receptor-deficient mice

The 5-HT receptor is the most recently identified receptor subtype within a family of 5-HT receptors activated by the neurotransmitter serotonin. There has been significant interest in investigating the potential role of this receptor in psychiatric disorders including depression, anxiety, and schizophrenia. Behaviors of 5-HT +/+ (wild-type or WT) and 5-HT -/- (receptor knockout or KO) mice were compared across 10 different assays (7 for anxiety, 1 for depression, 2 for psychosis) to identify differences that could indicate clinical potential for 5-HT receptor antagonism. Evaluation of KO vs. WT mice demonstrated significant differences between the genotypes in the fear conditioning, shock-probe burying, novelty-suppressed feeding, punishment memory, forced swim test, and d-amphetamine hyperactivity assays. There was not consistency in either the direction of behavioral effects across genotypes or across assays. Thus, data from these behavioral assays did not uniformly support the idea that 5-HT receptors constitute an important drug target for these psychiatric disorders. The present findings are generally congruent with the mixed results in the literature on the behaviors of 5-HT -/-mice and with the data on effects of 5-HT receptor antagonists in rodent models that detect activity of anxiolytic, antidepressant, and antipsychotic effects.