Figure 5. Neurohistogram showing response of a cardiac sympathetic Aδ-fibre (CV = 3.1 m s⁻¹) innervating the posterior wall of the left ventricle to 5 min of myocardial ischaemia before and after treatment with BQ-123 (0.1 mg kg⁻¹, i.v.).

A, 5 min of myocardial ischaemia increased baseline activity of this afferent from 0.39 to 2.42 imp s⁻¹. B, BQ-123 attenuated the increase (0.29 to 1.62 imp s⁻¹) in discharge activity of this afferent during repeated ischaemia, particularly the second peak of the biphasic response. Panels 1–4 are representative tracings of the discharge activity of the afferent at times indicated by the arrows above histograms.