Noradrenaline mediates slow excitatory synaptic potentials in rat dorsal raphe neurons in vitro

Repetitive focal stimulation to the slice surface within the region of the dorsal raphe (DR) nucleus of rat brain elicited a slow excitatory synaptic potential (slow EPSP), which followed a slow inhibitory synaptic potential (slow IPSP) in a majority of the DR neurons. The slow EPSPs were associated with either an increase of a decrease in membrane resistance. Noradrenaline (NA) application caused a membrane depolarization in most of the DR neurons. The NA-induced depolarization was also accompanied by either an increase or a decrease in membrane resistance. Both the slow EPSP and NA-induced depolarization were inhibited by phentolamine and prazosin but not by yohimbine and propranolol. The result suggests that slow EPSPs in rat DR neurons are mediated by NA interacting with an alpha 1-adrenoceptor.