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Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms.
J Physiol. 1993 Sep; 469:67-88.JP

Abstract

1. The calcium indicator dye, indo-1, was used to analyse the receptor-specific mechanisms of intracellular calcium ion ([Ca2+]i) responses evoked by excitatory amino acid (EAA) stimulation of dorsal horn neurons. Measurements of somal changes in [Ca2+]i were made on a subsecond time scale under conditions designed to allow membrane potential to mediate interactions between agonist-gated channels and voltage-gated calcium channels (VGCCs). 2. Voltage-gated calcium channels were activated in a receptor-independent manner using elevated extracellular [K+]. The concentration-dependence of K(+)-evoked [Ca2+]i transients was steep and variable among cells, with a mean maximal [Ca2+]i response of 1400 nM and a rapid maximal rate of rise. These data indicate that VGCCs provide a high-capacity route for Ca2+ entry that is very sensitive to small changes in membrane potential. 3. Stimulation of non-NMDA receptors using the non-desensitizing agonist kainate also evoked large [Ca2+]i responses (mean, 840 nM) that were predominantly due to indirect activation of VGCCs. However, in 60% of neurons tested, a component of the [Ca2+]i transient evoked by kainate at concentrations above 10 microM was not blocked by the potent VGCC blocker, lanthanum (La3+). The La(3+)-resistant [Ca2+]i responses to kainate rose exponentially, required extracellular Ca2+, and were caused neither by evoked release of EAA transmitters nor by reversal of Na(+)-Ca2+ exchange. These responses may be mediated by a Ca(2+)-permeable conformation of non-NMDA receptors and can also be evoked by quisqualate, (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and glutamate. 4. Non-NMDA receptors were activated in a desensitizing manner using quisqualate or AMPA. Quisqualate evoked small [Ca2+]i transients (210 nM) with a slow rate of rise. Typically, above 3 microM quisqualate, the size of the responses decreased, reflecting desensitization of the receptor. Responses to quisqualate were blocked by removal of extracellular Ca2+ indicating that mobilization of intracellular Ca2+ stores does not occur in the majority of dorsal horn neurons. However, trans-(+-)-1-amino-1,3-cyclopentane dicarboxylic acid (trans-ACPD) was occasionally able to evoke modest Ca2+ release. 5. Activation of the Ca(2+)-permeable NMDA receptors evoked [Ca2+]i transients that were large (780 nM), with a moderate rate of rise, and that generally achieved a maximum amplitude at NMDA concentrations around 300 microM. 6. Glutamate was used to examine [Ca2+]i responses to the activation of mixed EAA receptor subtypes by an endogenous ligand.(

ABSTRACT

TRUNCATED AT 400 WORDS)

Authors+Show Affiliations

Department of Physiology and Cellular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

7505825

Citation

Reichling, D B., and A B. MacDermott. "Brief Calcium Transients Evoked By Glutamate Receptor Agonists in Rat Dorsal Horn Neurons: Fast Kinetics and Mechanisms." The Journal of Physiology, vol. 469, 1993, pp. 67-88.
Reichling DB, MacDermott AB. Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms. J Physiol. 1993;469:67-88.
Reichling, D. B., & MacDermott, A. B. (1993). Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms. The Journal of Physiology, 469, 67-88.
Reichling DB, MacDermott AB. Brief Calcium Transients Evoked By Glutamate Receptor Agonists in Rat Dorsal Horn Neurons: Fast Kinetics and Mechanisms. J Physiol. 1993;469:67-88. PubMed PMID: 7505825.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Brief calcium transients evoked by glutamate receptor agonists in rat dorsal horn neurons: fast kinetics and mechanisms. AU - Reichling,D B, AU - MacDermott,A B, PY - 1993/9/1/pubmed PY - 1993/9/1/medline PY - 1993/9/1/entrez SP - 67 EP - 88 JF - The Journal of physiology JO - J Physiol VL - 469 N2 - 1. The calcium indicator dye, indo-1, was used to analyse the receptor-specific mechanisms of intracellular calcium ion ([Ca2+]i) responses evoked by excitatory amino acid (EAA) stimulation of dorsal horn neurons. Measurements of somal changes in [Ca2+]i were made on a subsecond time scale under conditions designed to allow membrane potential to mediate interactions between agonist-gated channels and voltage-gated calcium channels (VGCCs). 2. Voltage-gated calcium channels were activated in a receptor-independent manner using elevated extracellular [K+]. The concentration-dependence of K(+)-evoked [Ca2+]i transients was steep and variable among cells, with a mean maximal [Ca2+]i response of 1400 nM and a rapid maximal rate of rise. These data indicate that VGCCs provide a high-capacity route for Ca2+ entry that is very sensitive to small changes in membrane potential. 3. Stimulation of non-NMDA receptors using the non-desensitizing agonist kainate also evoked large [Ca2+]i responses (mean, 840 nM) that were predominantly due to indirect activation of VGCCs. However, in 60% of neurons tested, a component of the [Ca2+]i transient evoked by kainate at concentrations above 10 microM was not blocked by the potent VGCC blocker, lanthanum (La3+). The La(3+)-resistant [Ca2+]i responses to kainate rose exponentially, required extracellular Ca2+, and were caused neither by evoked release of EAA transmitters nor by reversal of Na(+)-Ca2+ exchange. These responses may be mediated by a Ca(2+)-permeable conformation of non-NMDA receptors and can also be evoked by quisqualate, (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and glutamate. 4. Non-NMDA receptors were activated in a desensitizing manner using quisqualate or AMPA. Quisqualate evoked small [Ca2+]i transients (210 nM) with a slow rate of rise. Typically, above 3 microM quisqualate, the size of the responses decreased, reflecting desensitization of the receptor. Responses to quisqualate were blocked by removal of extracellular Ca2+ indicating that mobilization of intracellular Ca2+ stores does not occur in the majority of dorsal horn neurons. However, trans-(+-)-1-amino-1,3-cyclopentane dicarboxylic acid (trans-ACPD) was occasionally able to evoke modest Ca2+ release. 5. Activation of the Ca(2+)-permeable NMDA receptors evoked [Ca2+]i transients that were large (780 nM), with a moderate rate of rise, and that generally achieved a maximum amplitude at NMDA concentrations around 300 microM. 6. Glutamate was used to examine [Ca2+]i responses to the activation of mixed EAA receptor subtypes by an endogenous ligand.(ABSTRACT TRUNCATED AT 400 WORDS) SN - 0022-3751 UR - https://www.unboundmedicine.com/medline/citation/7505825/Brief_calcium_transients_evoked_by_glutamate_receptor_agonists_in_rat_dorsal_horn_neurons:_fast_kinetics_and_mechanisms_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0022-3751&date=1993&volume=469&spage=67 DB - PRIME DP - Unbound Medicine ER -