Figure 4. Summary of pooled ED₅₀ data for brachycardia, apnoea and hyperventilation evoked by αβ-MeATP.

Mean apparent ED₅₀ values ± s.e.m. for reflex changes evoked by i.v. αβ-MeATP before (Control, n = 14) and after various procedures in rats anaesthetized with pentobarbitone. A, bradycardia was significantly reduced by atropine (2.8 μmol (kg body wt)⁻¹, n = 4), bilateral vagotomy (n = 3), suramin (14 μmol (kg body wt)⁻¹, n = 3) and by PPADS (17 μmol (kg body wt)⁻¹, n = 4), but unaffected by MDL 72222 (0.24 μmol (kg body wt)⁻¹, n = 2) or cutting the sinus nerves (Cut CNS, n = 3). B, apnoea was unaffected by atropine (n = 4), MDL 72222 (n = 3), or cutting the carotid sinus nerves (n = 4), but was reduced after vagotomy (n = 5), suramin (n = 4) or PPADS (n = 4). C, hyperventilation was reduced by cutting the carotid sinus nerves (n = 4), and slightly but significantly by MDL 72222 (n = 4). The response was potentiated by vagotomy (n = 5) or PPADS (n = 4), and unaffected by atropine or suramin (both n = 4). *P < 0.05 versus control values (Mann-Whitney test).