Rat atriopeptin III alters hypothalamic neuronal activity

Abstract The effect of pressure application of rat atriopeptin III on extracellularly recorded action potentials of 39 hypothalamic neurons was studied in chloral hydrate-anesthetized male rats. Thirteen of these neurons were histologically located within the boundaries of the paraventricular nucleus. Atriopeptin III was a potent inhibitor of the spontaneous activity of 5 (38%) of these neurons and increased the spontaneous activity of one (8%) other neuron (7 paraventricular neurons were unresponsive to atriopeptin III). Neurons not located within the paraventricular nucleus responded similarly to pressure application of atriopeptin III. Twenty-seven percent (n=7) were inhibited and 12% (n=3) were excited while the remaining 16 (61%) neurons were unresponsive to atriopeptin III. Similar applications of an inactive fragment of atriopeptin III (amino acid sequence 18–28) did not alter the spontaneous activity of any neuron (n=6). These results illustrate that atriopeptin III, an atrial peptide which is also present in the brain, can alter the spontaneous activity of hypothalamic neurons. This provides additional evidence for central activity of this peptide.