Release of a neurodepressing hormone from the crustacean sinus gland

The nervous system of the crayfish contains a peptide of low molecular weight which depresses the spontaneous electrical activity of motoneurons in the abdominal ganglia. Most of this substance is contained in the sinus gland, a neurohemal organ in the eyestalk. Electrical stimulation of the isolated sinus gland, or its incubation in potassium-rich solutions (20--80 mM) results in the release of the neurodepressing peptide. The release is calcium-dependent and appears to involve a process of exocytosis. The released product shows electrophoretic properties undistinguishable from the substance present in the sinus gland.