Figure 4. Neurohistogram showing response of a cardiac sympathetic C-fibre (CV = 0.32 m s⁻¹) innervating the posterior wall of the left ventricle to ET-1 (2 μg, LA) before and after treatment with BQ-123 (0.1 mg kg⁻¹, i.v.).

A, administration of ET-1 increased baseline activity of this afferent from 0.68 to 1.81 imp s⁻¹. B, BQ-123 abolished the increase (0.74 to 0.73 imp s⁻¹) in discharge activity of this afferent during repeated injection off ET-1. Panels 1 and 2 are representative tracings of the discharge activity of the afferent at times indicated by the arrows above histograms.