Cranial nerve visceral afferents enter the brainstem to synapse on neurons within the solitary tract nucleus (NTS). The broad heterogeneity of both visceral afferents and NTS neurons makes understanding afferent synaptic transmission particularly challenging. To study a specific subgroup of second-order neurons in medial NTS, we anterogradely labeled arterial baroreceptor afferents of the aortic depressor nerve with lipophilic fluorescent tracer (i.e. ADN+) and measured synaptic responses to solitary tract (ST) activation recorded from dye-identified neurons in medial NTS in horizontal brainstem slices. Every ADN+ NTS neuron received constant-latency ST-EPSCs (jitter <192 µs, SD of latency). Stimulus-recruitment profiles showed single thresholds and no suprathreshold recruitment - findings consistent with EPSCs arising from a single, branched afferent axon. Frequency-dependent depression of ADN+ EPSCs averaged ~70% for five shocks at 50 Hz but single-shock failure rates did not exceed 4%. Whether adjacent ADN- or those from unlabeled animals, other second-order NTS neurons (jitters <200 µs) had ST transmission properties indistinguishable from ADN+. Capsaicin (CAP, 100 nM) blocked ST transmission in some neurons. CAP-sensitive ST-EPSCs were smaller and failed >5x more frequently than CAP-resistant responses whether ADN+ or from unlabeled animals. Variance-mean analysis of ST-EPSCs suggested uniformly high probabilities for quantal glutamate release across second-order neurons. While amplitude differences may reflect different numbers of contacts, higher frequency-dependent failure rates in CAP-sensitive ST-EPSCs may arise from subtype-specific differences in afferent axon properties. Thus, afferent transmission within medial NTS differed by axon class (e.g. CAP-sensitive) but was indistinguishable by source of axon (e.g. baroreceptor vs. non-baroreceptor).