title: Presynaptic glutamate receptor--possible involvement of a K+ channel.
abstract: Intra-axonal recording was made from the excitatory axon of the lobster walking leg near the nerve terminal and the effects of L-glutamate were studied. Topical application of glutamate to the synapse produced hyperpolarization in the presynaptic membrane with increase in conductance. The glutamate-induced hyperpolarization was reversed to a depolarization at about -100 mV. The reversal potential was not significantly changed by altering the external Cl- but was shifted to more positive values by increasing the external K+. A spider toxin (JSTX), which specifically blocks the postsynaptic glutamate receptor, failed to block the presynaptic glutamate potential. The results suggest that the presynaptic membrane of the lobster neuromuscular synapse has a different type of glutamate receptor from those in the postsynaptic membrane.
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D005971:Glutamates / Q000502:physiology*; D008564:Membrane Potentials; D008121:Nephropidae / Q000502:physiology*; D009451:Neuroeffector Junction / Q000502:physiology; D009498:Neurotoxins / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology; D013111:Spider Venoms / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
chemical_list: D005971:Glutamates; C044936:JSTX spider toxin; D009498:Neurotoxins; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D013111:Spider Venoms; D011188:Potassium