Pharmacological Evidence for Cannabinoid Receptors in Glutamatergic Synapses at the Crayfish Neuromuscular Junction

Abstract

Endogenous cannabinoids and cannabinoid receptors are involved in retrograde messaging in neurons, a system believed to be restricted to the vertebrate nervous system. However, recent studies have begun to find evidence of both endogenous cannabinoids and their receptors in some invertebrates as well as at the neuromuscular junction of vertebrates. This experiment represents our attempts to link these two distinct areas of cannabinoid research by looking for evidence of cannabinoid receptors in the glutamatergic neuromuscular junction of crayfish (Procambarus clarkii). Using a combination of standard electrophysiological techniques and the chemical application of cannabinoid receptor agonists and cannabinoid receptor antagonists, we measured the excitatory post synaptic potentials (EPSPs) at this neuromuscular junction and compared the amplitudes of the EPSPs during the application of agonist, antagonist, and agonist with pre-applied antagonist. These data suggest that there are in fact cannabinoid receptors in the crayfish neuromuscular junction and that these receptors play a role in mediating synaptic inhibition. This research has the potential to redefine the evolutionary history of cannabinoids receptors and augment our current understanding of their role in the nervous system.