Two distinct quisqualate receptors regulate Ca2+ homeostasis in hippocampal neurons in vitro.
Addition of quisqualate to mouse hippocampal neurons in vitro elicited two types of changes in [Ca2+]i as assessed by fura-2-based microfluorimetry. The first was a transient spike or group of oscillations and the second was a long lasting "plateau" response. The long-lasting response was abolished on removal of either Ca2+ or Na+ from the external medium or by blocking voltage-sensitive Ca2+ channels. Furthermore, the novel glutamate antagonist 6-nitro-7-cyano-quinoxaline-2,3-dione was a competitive inhibitor of this response. In contrast, none of these manipulations abolished the transient [Ca2+]i spike. Transient [Ca2+]i spikes or oscillations could also be produced by the alpha 1-adrenergic agonist phenylephrine. Production of such an alpha 1-response reduced the size of a subsequently elicited quisqualate response. However production of transient [Ca2+]i spikes with caffeine did not alter the size of the quisqualate-induced spike. We conclude that hippocampal neurons possess two different types of quisqualate receptors. The first mediates quisqualate-induced depolarization and the second mediates Ca2+ mobilization from intracellular stores.
Murphy
S N
SN
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
Miller
R J
RJ
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D006706:Homeostasis; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000096:biosynthesis; D051379:Mice; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D016318:Quisqualic Acid; D018091:Receptors, AMPA; D017981:Receptors, Neurotransmitter / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D015220:Calcium Channels; D005971:Glutamates; D007295:Inositol Phosphates; D010069:Oxadiazoles; D011810:Quinoxalines; D018091:Receptors, AMPA; D017981:Receptors, Neurotransmitter; D018698:Glutamic Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015544:Inositol 1,4,5-Trisphosphate; D016318:Quisqualic Acid; D002118:Calcium