Release of a neurosecretory protein from the corpora cardiaca of Locusta migratoria induced by high potassium saline and compound action potentials

Abstract

Electrical stimulation of nervus corpus cardiacum I (NCCI) resulted in the propagation of a compound action potential into the storage and glandular lobes of the corpus cardiacum (CC) of Locusta migratoria. The compound action potential was abolished in the presence of both sodium-free saline and tetrodotoxin (TTX). Calcium-free saline had variable effects. The release of a neurosecretory protein (estimated following precipitation with an antiserum directed against neurosectetory protein) was examined after treatment with high potassium saline and electrical stimulation of NCC I. Release was induced by elevated potassium salines and by the propagation of a compound action potential along NCC I. The release was calcium-dependent. TTX and sodium-free saline abolished the electrically-induced release of protein. Concomitant with the release of protein was the release of a factor with diuretic activity, illustrating that hormones are also being released along with the neurosecretory protein. The release of this protein was dependent upon the frequency of electrical stimulation (up to approx. 5 Hz) and the patterning of electrical stimulation. This neurosecretory protein which has previously been shown to be very similar in both size and amino acid composition to the pituitary neurophysins, now also shares the characteristic of being released along with hormone.