Responsiveness of intrinsic cardiac neurons to left atrial and hypothalamic cardioactive peptides

This study was designed to investigate whether cardioactive peptides derived from left atrial tissue or the hypothalamus modulate neurons within the intrinsic cardiac nervous system. Peptides derived from left atrial or left auricular tissues with known coronary artery dilator properties were administered (0.1 ml; 100 microM dose) individually over 10-s periods into the arterial blood supply of ventral ventricular neurons in 11 anesthetized pigs (19-28 kg). Similarly, three hypothalamic protein-hormonal complexes that express coronary artery vasodilator properties, protein-hormone complexes C, G and K, were studied. Each peptide modified the activity generated by some of the neurons identified in a locus of the ventral ventricular ganglionated plexus of each animal. The hypothalamic peptides elicited primarily excitatory responses, whereas the atrial ones induced more suppressor than excitatory responses. Cardiovascular indices remained unchanged overall, indicating that observed neuronal effects were not secondary to cardiodynamic alterations. These data indicate that intrinsic cardiac neurons are sensitive to left atrial and hypothalamic peptides that exhibit coronary artery dilator properties.