Dorsal root ganglion (DRG) neurones express a unique repertoire of ion channels, including the tetrodotoxin-resistant (TTX-R) low-threshold Na⁺ channel Nav1.9/NaN and the low-threshold T-type Ca²⁺ channel(s). These channels have been shown to be implicated in the molecular mechanisms of pain transmission. As part of ongoing work aimed at illuminating the functional role of Nav1.9 and T-type Ca²⁺ channels (ICaT) in sensory neurones, we have used whole-cell patch clamp recording combined with pharmacological methods to determine the relative contribution of Nav1.9 and ICaT to low-threshold (LVA) currents in acutely dissociated rat DRG neurons. We showed that amiloride blocked ICaT whereas it had no effects on Nav1.9 as well as Nav1.8/SNS currents. We next sought to characterize NaN/Nav1.9 currents pharmacologically using amiloride as a discriminating tool. Nav1.9/NaN was inhibited by various inorganic Ca²⁺ channel blockers with the following rank of potency (IC50, µM): La³⁺ (46) > Cd²⁺ (234) > Ni²⁺ (893). We then devised a classification system based on several characteristics, including cell body diameter, capsaicin sensitivity and the presence and properties of NaN/Nav1.9, ICaT and mechanosensitive cation currents. Cluster analysis identified 2 subpopulations among the C-heat nociceptive cells (Cm from 14-40 pF, n = 68). These 2 groups had identical Nav1.9 current density but significantly different densities of amiloride-sensitive ICaT (group-I: 6.5 ± 1 pA/pF; group-II: 35 ± 5 pA/pF). In addition, group-II C-heat nociceptive cells exhibited an amiloride-resistant ICaT (5.5 ± 2 pA/pF). Cells clustered in group-I displayed high-threshold slowly-adapting mechanically-activated currents whereas group-II cells had mechanically-activated currents which failed to adapt during the entire length of mechanical stimuli. We identified a third population of nociceptive cells that made up ~35 % of the capsaicin-responsive cell population, and which fell mainly within the medium cell range (Cm = 35-70 pF, n = 37), possibly corresponding to type Aδ DRG cells. This cell subset was not mechanosensitive and had very large NaN/Nav1.9 current (37.2 ± 3 pA/pF) and relatively small amiloride-sensitive ICaT (18.5 ± 4 pA/pF). In conclusion, this study shows that Nav1.9 and T-type Ca²⁺ currents are co-expressed in C-type and Aδ nociceptors and cannot be distinguished by their sensitivity to inorganic Ca²⁺ channels. In addition, the use of amiloride as a discriminating tool allowed us to identify 2 subpopulations of C-type nociceptors that may be distinguished by their relative expression of NaN/Nav1.9, T-type Ca²⁺ currents and mechanosensitive cation currents. Results are presented as mean ± SEM.