I used whole-cell voltage clamp and current clamp recordings in acute mouse olfactory bulb slices. I first demonstrate that a population of juxtaglomerular interneurons, which release both dopamine and GABA, can effectively inhibit transmitter release from primary afferent neurons, thereby potently controlling the strength of afferent input. Using single glomerular afferent stimulation, I further demonstrate that the afferent olfactory receptor nerve terminal has an extraordinarily high release probability, which is mediated by a single pool of slowly recycling vesicles. This work provides important insight into the divergent synaptic processing of common olfactory input, and defines the synaptic mechanisms underlying parallel processing of afferent input.