Changes in Synaptic Transmission Following Bath Application or Microinjection of Phospholipase A2 Neurotoxins in Paired Cholinergic Neurons of Aplysia Buccal Ganglia
Abstract
Taipoxin, crotoxin, and corticotoxin I (C1) were tested to determine the site of action of snake neurotoxins having phospholipase A2 (PLA2) activity, using cholinergically coupled neurons of buccal ganglia of the marine mollusc Aplysia california. Corticotoxin II (C2), a neurotoxin that lacks PLA2 activity, was also studied. The toxins were bath applied or pressure injected into presynaptic neurons. Resting membrane potentials (RMP), action potentials, and amplitude and time course of inhibitory postsynaptic potentials (IPSPs) were measured electrophysiologically. Injection or bath superfusion of all toxins usually resulted in a transient change of less than 20% in the RMP in pre- and postsynaptic cells. Injections of PLA2 toxins into presynaptic neurons transiently increased IPSP amplitudes, indicating increased transmitter release. This effect was followed by time-dependent decreases in evoked IPSP amplitudes. C2 toxin, in contrast, only decreased IPSP amplitudes. Bath application of all toxins resulted in decreased IPSP amplitudes. However, bath application of toxins also resulted in increased spontaneous postsynaptic action potentials and IPSPs, suggesting effects on potassium channels. These observations suggest multiple intracellular and extracellular sites of action, in both pre- and postsynaptic neurons.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2000
- Accession Number
- ADA385878
Entities
People
- Clarence A. Broomfield
- J. L. Middlebrook
- James P. Apland
- Margaret G. Filbert
- Mary L. Winfree
Organizations
- United States Army Medical Research Institute of Chemical Defense