Dopamine’s secret agent: serotonin

Dopamine suppresses GABA release from striatal terminals in the substantia nigra pars reticulata. Molinari et al. recently demonstrated that this suppression is frequency-dependent-instituting a high-pass filter on striatal 'direct pathway' transmission-and does not require dopamine receptors. Rather, dopamine upregulates serotonin, activating presynaptic 5HT1B receptors to exert its effects.