Postsynaptic Glutamate Receptors in the Crayfish Neuromuscular Junction Appear Pharmacologically Similar in the Presence of Strychnine

Abstract

For more than a decade, glutamatergic transmission, the examination of various types of glutamate receptors, and their link to learning and memory have been studied in vertebrate nervous systems. However, very few experiments have been carried out regarding this aspect of glutamatergic transmission in invertebrates, which often hold vital clues to the understanding of the nervous systems of higher organisms. As a first step in exploring this subject, we designed an experiment, focused on glutamate and its receptors in the neuromuscular junction of the crayfish, to see if a single postsynaptic cell has multiple receptors for the same neurotransmitter. We measured, through intracellular recording, the number of neurons innervating a muscle cell in response to a stimulus, while the sample was bathed in standard saline crayfish solution (pH 7.4). Each innervating neuron could be seen as an increasing step in relation to our first measured EPSP and was directly correlated to an increase in voltage. We then repeated the procedure while the crayfish was immersed in another saline solution containing the glutamate antagonist, strychnine. Our results showed that the glutamate antagonist equally blocked the receptors responding to the different neurons even after prolonged washing with a non-strychnine solution. This led us to conclude that in the presence of strychnine, postsynaptic glutamate receptors appear to be pharmacologically similar.