Glomus cell heterogeneity underpins distinct carotid body chemoreflex pathways: implications for hypertension

The carotid body (CB) is a multimodal chemosensory organ, yet how it encodes differential external stimuli to drive distinct peripheral chemoreflex responses remains unclear. This study aimed to define differences in intrinsic cellular mechanisms underlying CB signalling and to investigate how these processes are altered in pre-hypertension.

We used potassium cyanide (KCN) as a hypoxia mimetic to activate the CB.K+ channels implicated in hypoxia sensing were pharmacologically inhibited, with TWIK-related acid-sensitive K+ (TASK) channels targeted using Ba2+ or ML365 and BK/Kv channels targeted using TEA + 4AP or iberiotoxin. We combined in vitro Ca2+ imaging of dissociated glomus cells, ex vivo carotid sinus nerve (CSN) recordings, and an in situ double-perfused working heart-brainstem preparation to investigate chemosensory signalling in juvenile Wistar and age-matched pre-hypertensive spontaneously hypertensive rats (SHRs). KCN application to the CB ex vivo evoked a biphasic CSN response, consisting of two temporally distinct components. This biphasic response was exaggerated in SHRs, with disproportionate changes in the magnitude of each component. Ca2+ imaging revealed that these components reflect distinct glomus cell subpopulations, characterized by transient vs. prolonged KCN-evoked Ca2+ events, with their relative proportions shifted in hypertension. Pharmacological dissection suggested that differential inactivation of K+ channels contributes to these divergent Ca2+ dynamics. In situ, we confirmed that localized Ba2+ applied to the CB facilitated stronger tachypnoeic and bradycardic chemoreflex evoked responses than TEA + 4AP, consistent with functional heterogeneity among glomus cell populations. Compared with Wistar rats, in vitro TASK and BK/Kv channel expression and activity were differentially altered in SHRs, accompanied by corresponding changes in in situ chemoreflex characteristics.

We identify, for the first time, distinct glomus cell subpopulations defined by their K+ channel expression that differentially contribute to CB signalling patterns and distinct chemoreflex pathways. These findings provide mechanistic support for the recently proposed 'ribbon cable' hypothesis, whereby discrete glomus cell populations couple to specific chemoreflex outputs. These findings offer new insight into CB signalling complexity and its role in autonomic dysfunction during the early stages of hypertension.