NATURE OF THE CARDIOEXCITOR NEUROHORMONE IN AN ARACHNID POECILOTHERIA FASCIATA SCHNEIDER (ARANEIDA)

Abstract

SUMMARY The heart of Poecilotheria fasciata (Arachnida, Theraphosidas) is regulated by a neurohormone present in the brain and heart tissues. Structural modifications of stainable neurosecretory materials were found in the heart tissue submitted to electrical stimulation. The neurohormone is thermostable and dialysable but is inactivated by trypsin and migrates towards the anode in the electrical field. These properties together with its amino acid composition suggest that the neurohormone may be a peptide.