Delta glutamate receptor conductance drives excitation of mouse dorsal raphe neurons.

The dorsal raphe nucleus is the predominant source of central serotonin, where neuronal activity regulates complex emotional behaviors. Action potential firing of serotonin dorsal raphe neurons is driven via α1-adrenergic receptors (α1-A) activation. Despite this crucial role, the ion channels responsible for α1-A-mediated depolarization are unknown. Here, we show in mouse brain slices that α1-A-mediated excitatory synaptic transmission is mediated by the ionotropic glutamate receptor homolog cation channel, delta glutamate receptor 1 (GluD1). GluD1-channels are constitutively active under basal conditions carrying tonic inward current and synaptic activation of α1-As augments tonic GluD1-channel current. Further, loss of dorsal raphe GluD1-channels produces an anxiogenic phenotype. Thus, GluD1-channels are responsible for α1-A-dependent induction of persistent pacemaker-type firing of dorsal raphe neurons and regulate dorsal raphe-related behavior. Given the widespread distribution of these channels, ion channel function of GluD1 as a regulator of neuronal excitability is proposed to be widespread in the nervous system.