Summary
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1.
The effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata were studied.
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2.
At concentrations of 10-3 to 10-6 M, l-glutamic acid diethylester (GDEE) and l-glutamic acid dimethylester (GDME) decreased the resting afferent discharge frequency as well as the electrically evoked activities and depressed the responses to application of excitatory amino acids.
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3.
d-α-Aminoadipic acid (AA) and 2-amino-4 phosphonobutyric acid (APB) had practically no effect either on resting afferent discharge or on evoked afferent activity.
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4.
2-Amino-5-phosphonovaleric acid (APV) reduced the resting afferent discharge and electrically evoked activity in the afferent fibres. APV blocked N-methyl-d-aspartate (NMDA) induced responses at a lower concentration than those induced by aspartate.
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5.
Responses caused by NMDA were Mg2+-dependent; those to quisqualate (Q) application depended to a lesser degree on the Mg2+ concentration.
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6.
Cis-2,3-piperidinedicarboxylic acid (PDA) blocked both the resting afferent discharge and the electrically evoked activity; it also reversibly blocked the postsynaptic, amino acid-induced responses. The l-glutamate (l-GLU) response was more resistant to the blockade than the l-aspartate (l-ASP) response.
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7.
Both kynurenic acid (KEN) and γ-d-glutamylglycine (DGG) reduced the resting and evoked activities in the afferent fibres. l-ASP was more resistant to blockade by KEN than l-GLU.
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8.
These observations suggest a prominent physiological role of quisqualate-, kainate- and NMDA-preferring receptors in the ampullae of Lorenzini of Raja clavata.
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Abbreviations
- AA :
-
d-α-Aminoadipic acid
- APB :
-
2-Amino-4 phosphonobutyric acid
- APV :
-
2-Amino-5-phosphonovaleric acid
- DGG :
-
γ-d-glutamylglycine
- GDEE :
-
l-glutamic acid diethylester
- GDME :
-
l-glutamic acid dimethylester
- l-ASP :
-
l-aspartate
- l-GLU :
-
l-glutamate
- KEN :
-
kynurenic acid
- NMDA :
-
N-methyl-d-aspartate
- PDA :
-
Cis-2,3-piperidinecarboxylic acid
- Q :
-
quisqualate
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Akoev, G.N., Andrianov, G.N., Bromm, B. et al. Effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata . J Comp Physiol A 168, 647–652 (1991). https://doi.org/10.1007/BF00224355
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DOI: https://doi.org/10.1007/BF00224355