DZNE - German Center for Neurodegenerative Diseases Mar 28 2025 Long-term fasting in 24-hour cycles increases the sex drive of male mice by lowering the concentration of the neurotransmitter serotonin in the brain. This effect is linked to a diet-induced deficiency of the precursor substance tryptophan – an amino acid that must be obtained through food. Researchers from DZNE report on this in the journal Cell Metabolism , together with a Chinese team from Qingdao University and the University