This difference makes the SERT–/– rat a further attractive model to test the different 5-HT1A receptor-modulating drugs, F15599, F13714 and S-15355, as it may provide information on the adaptation of pre- and post-synaptic 5-HT1A receptors due to chronic high 5-HT levels, which may aid in the treatment of sexual dysfunction caused by SSRI treatment. The gene discussed is HTR1A; the disease is sexual dysfunction.