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Localization of glutamate and glutamate transporters in the sensory neurons of Aplysia
Author(s) -
Levenson Jonathan,
Sherry David M.,
Dryer Laurence,
Chin Jeannie,
Byrne John H.,
Eskin Arnold
Publication year - 2000
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/1096-9861(20000717)423:1<121::aid-cne10>3.0.co;2-e
Subject(s) - glutamate receptor , biology , neuropil , neuroscience , sensory system , neurotransmitter , metabotropic glutamate receptor 6 , glutaminase , sensory neuron , synapse , glutamatergic , metabotropic glutamate receptor , biochemistry , central nervous system , receptor
The sensorimotor synapse of Aplysia has been used extensively to study the cellular and molecular basis for learning and memory. Recent physiologic studies suggest that glutamate may be the excitatory neurotransmitter used by the sensory neurons (Dale and Kandel [1993] Proc Natl Acad Sci USA. 90:7163–7167; Armitage and Siegelbaum [1998] J Neurosci. 18:8770–8779). We further investigated the hypothesis that glutamate is the excitatory neurotransmitter at this synapse. The somata of sensory neurons in the pleural ganglia showed strong glutamate immunoreactivity. Very intense glutamate immunoreactivity was present in fibers within the neuropil and pleural‐pedal connective. Localization of amino acids metabolically related to glutamate was also investigated. Moderate aspartate and glutamine immunoreactivity was present in somata of sensory neurons, but only weak labeling for aspartate and glutamine was present in the neuropil or pleural‐pedal connective. In cultured sensory neurons, glutamate immunoreactivity was strong in the somata and processes and was very intense in varicosities; consistent with localization of glutamate in sensory neurons in the intact pleural‐pedal ganglion. Cultured sensory neurons showed only weak labeling for aspartate and glutamine. Little or no γ‐aminobutyric acid or glycine immunoreactivity was observed in the pleural‐pedal ganglia or in cultured sensory neurons. To further test the hypothesis that the sensory neurons use glutamate as a transmitter, in situ hybridization was performed by using a partial cDNA clone of a putative Aplysia high‐affinity glutamate transporter. The sensory neurons, as well as a subset of glia, expressed this mRNA. Known glutamatergic motor neurons B3 and B6 of the buccal ganglion also appeared to express this mRNA. These results, in addition to previous physiological studies (Dale and Kandel [1993] Proc Natl Acad Sci USA. 90:7163–7167; Trudeau and Castellucci [1993] J Neurophysiol. 70:1221–1230; Armitage and Siegelbaum [1998] J Neurosci. 18:8770–8779)) establish glutamate as an excitatory neurotransmitter of the sensorimotor synapse. J. Comp. Neurol. 423:121–131, 2000. © 2000 Wiley‐Liss, Inc.