--- - |2+ Cardiac sympathetic over‐activity is a well‐established contributor to the progression of neurogenic hypertension and heart failure, yet the underlying pathophysiology remains unclear. Recent studies have highlighted the importance of acutely regulated cyclic nucleotides and their effectors in the control of intracellular calcium and exocytosis. Emerging evidence now suggests that a significant component of sympathetic over‐activity and enhanced transmission may arise from impaired cyclic nucleotide signalling, resulting from compromised phosphodiesterase activity, as well as alterations in receptor‐coupled G‐protein activation. In this review, we address some of the key cellular and molecular pathways that contribute to sympathetic over‐activity in hypertension and discuss their potential for therapeutic targeting. This article is protected by copyright. All rights reserved - The Journal of Physiology, Volume 0, Issue ja, -Not available-.