Presynaptic actions of glutamate receptor agonists in the CA1 region of rat hippocampus in vitro.
A grease-gap recording technique which allows the monitoring of presynaptic d. c. potentials without contamination of potentials from postsynaptic elements was used to examine presynaptic actions of glutamate agonists in the CA1 region of rat hippocampus. Presynaptic depolarizations through the activation of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)- and 2-amino-5-phosphonovaleric acid (APV)-sensitive receptors could be induced by applied agonists. In addition, the N-methyl-D-aspartate (NMDA)-induced depolarization was smaller in the presence of extracellular Mg2+ suggesting some similarity to postsynaptic NMDA receptors. The (1S,3R)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD)-induced depolarization was antagonized by L-2-amino-3-phosphonopropionic acid (L-AP3) but was also sensitive to APV+CNQX, creating ambiguity as to the type of receptors involved. These results suggest that the activation of glutamate autoreceptors leads to a presynaptic depolarization.
Department of Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada.
T R
TR
Shew
W
W
Morishita
B R
BR
Sastry
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects*; D066298:In Vitro Techniques; D008274:Magnesium / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D017661:Receptors, Presynaptic / Q000187:drug effects*
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D015221:Potassium Channels; D016194:Receptors, N-Methyl-D-Aspartate; D017661:Receptors, Presynaptic; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D018698:Glutamic Acid; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D008274:Magnesium