Cardiovascular responses produced by activation of P2X purinergic receptors in the lateral parabrachial nucleus

Abstract

Recent studies have shown that purinergic mechanisms of the lateral parabrachial nucleus (LPBN) are involved in the control of sodium intake. In the present study, we investigated the effects of injections of α,β‐methylene adenosine 5′‐triphosphate (α,β‐meATP, a selective P2X purinergic receptor agonist) alone or combined with the P2X purinergic receptor antagonist PPADS (pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulfonic acid) into the LPBN on mean arterial pressure (MAP) and heart rate (HR) in awake rats. Male Holtzman rats (n = 6), baseline MAP = 102 ± 2 mmHg and baseline HR = 376 ± 10 bpm, with stainless steel guide‐cannulas implanted in the LPBN and with a polyethylene tubing (PE‐10 connected to a PE‐50) inserted into abdominal aorta through femoral artery were used. Unilateral injection of α,β‐meATP (2.0 nmol/0.2 μl) into the LPBN increased MAP (15 ± 2 mmHg, vs. saline: 4 ± 1 mmHg), without changing HR. The pressor response to α,β‐meATP injected into the LPBN was attenuated by previous injection of PPADS (4.0 nmol/0.2 μl) into the LPBN (3 ± 1 mmHg). Unilateral injection of PPADS alone into the LPBN produced no change on baseline MAP and HR. The results suggest that α,β‐meATP acting on P2X purinergic receptors in the LPBN produces pressor responses without changing HR. Financial support: FAPESP, CNPq.