ABSTRACT
A vasoactive intestinal peptide (VIP)-like peptide is released by axonal stimulation in the giant axon–Schwann cell preparation from the tropical squid Sepioteuthis sepioidea. It is also released by direct application of L-glutamate, the giant axon–Schwann cell signalling molecule in this preparation. The release of the peptide parallels the release of acetylcholine from the Schwann cells themselves in this preparation in a number of different ways. The release of both acetylcholine and the VIP-like peptide have the same threshold (between 2×10−10 and 5×10−10 mol l−1) for L-glutamate application and the same recovery time after inhibition of release by exposure of the preparation to a prolonged pulse of L-glutamate. A prolonged L-glutamate pulse of 10−8 mol l−1 releases both substances for as long as the pulse is applied to the preparation, whereas a prolonged pulse of 10−9 mol l−1 L-glutamate releases acetylcholine in the same way but releases the VIP-like peptide only transiently. The VIP-like peptide is likely to be co-released with acetylcholine from the Schwann cells.
