Related Experiment Video
Updated: Aug 15, 2026

Physiological Experimentation with the Crayfish Hindgut: A Student Laboratory Exercise
Published on: January 18, 2011
The action of vasoactive intestinal peptide antagonists on peptidergic modulation of the squid Schwann cell
1Department of Zoology, University of Cambridge.
Abstract:
1. The effects of two specific antagonists of vasoactive intestinal peptide (VIP) receptors were investigated on the VIP-induced hyperpolarization of the membrane potential of the Schwann cell of the giant nerve fibre of the tropical squid. 2. Both (pCl-D-Phe6,Leu17)VIP and (N-Ac-Tyr1,D-Phe2)-GRF(1-29)amide competitively and reversibly blocked the effects of VIP in this preparation with the former compound being more potent than the latter. 3. The blocking actions of both antagonists were specific for the responses of this preparation to VIP. They did not block the actions of carbachol, DL-octopamine or substance P. 4. Both antagonists also reduced the effectiveness of an endogenous VIP-like component in the normal hyperpolarizing action of giant axon activity on the membrane potential of the Schwann cell, with the same potency ratio as for their actions on the effects induced by the exogenous application of VIP.
Related Concept Videos
Action Potentials
Action Potential
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Ligand-Gated Ion Channel Receptor: Gating Mechanism
Indirect-Acting Cholinergic Agonists: Pharmacological Actions
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...
Nondepolarizing (Competitive) Neuromuscular Blockers: Mechanism of Action
Competitive antagonists prevent acetylcholine from binding to its receptor, inhibiting membrane depolarization. Without conformational changes or intrinsic...
Action Potential
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...

