title: Protein kinase C-dependent potentiation of intracellular calcium influx by sigma1 receptor agonists in rat hippocampal neurons.
abstract: Intracellular calcium concentration ([Ca2+]i) plays a major role in neuronal excitability, especially that triggered by the N-methyl-d-aspartate (NMDA)-sensitive glutamatergic receptor. We have previously shown that sigma1 receptor agonists potentiate NMDA receptor-mediated neuronal activity in the hippocampus and recruit Ca2+-dependent second messenger cascades (e.g., protein kinase C; PKC) in brainstem motor structures. The present study therefore assessed whether the potentiating action of sigma1 agonists on the NMDA response observed in the hippocampus involves the regulation of [Ca2+]i and PKC. For this purpose, [Ca2+]i changes after NMDA receptor activation were monitored in primary cultures of embryonic rat hippocampal pyramidal neurons using microspectrofluorometry of the Ca2+-sensitive indicator Fura-2/acetoxymethyl ester in the presence of sigma1 agonists and PKC inhibitors. We show that successive activations of the sigma1 receptor by 1-min pulses of (+)-benzomorphans or (+)-N-cyclopropylmethyl-N-methyl-1,4-diphenyl-1-ethyl-but-3-en-1-ylamine hydrochloride (JO-1784) concomitantly with glutamate time dependently potentiated before inconstantly inhibiting the NMDA receptor-mediated increase of [Ca2+]i, whereas 1,3-di-o-tolyl-guanidine, a mixed sigma1/sigma2 agonist, did not significantly modify the glutamate response. Both potentiation and inhibition were prevented by the selective sigma1 antagonist N,N-dipropyl-2-[4-methoxy-3-(211phenylethoxy) phenyl]-ethylamine monohydrochloride (NE-100). Furthermore, only (+)-benzomorphans could induce [Ca2+]i influx by themselves after a brief pulse of glutamate. A pretreatment with the conventional PKC inhibitor 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo [2,3-a] pyrrolo [3,4-c] carbazole (Gö-6976) prevented the potentiating effect of (+)-benzomorphans on the glutamate response. Our results provide further support for a general mechanism for the intracellular sigma1 receptor to regulate Ca2+-dependent signal transduction and protein phosphorylation.
authors.affiliation: Hôpital Charcot, and Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 488, 80 rue du Général Leclerc, F-94276 Kremlin-Bicêtre cedex, France. monnet@kb.inserm.fr
authors.forename: F P
authors.initials: FP
authors.lastname: Monnet
authors.forename: M P
authors.initials: MP
authors.lastname: Morin-Surun
authors.forename: J
authors.initials: J
authors.lastname: Leger
authors.forename: L
authors.initials: L
authors.lastname: Combettes
mesh_terms: D000818:Animals; D000840:Anisoles / Q000494:pharmacology; D001575:Benzomorphans / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D002934:Cinnamates / Q000494:pharmacology; D003521:Cyclopropanes / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D007211:Indoles / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011437:Propylamines / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017480:Receptors, sigma / Q000819:agonists*
chemical_list: D000840:Anisoles; D001575:Benzomorphans; D002227:Carbazoles; D002934:Cinnamates; D003521:Cyclopropanes; D004791:Enzyme Inhibitors; D006146:Guanidines; D007211:Indoles; D011437:Propylamines; D017480:Receptors, sigma; C101491:sigma1-binding protein, rat; C081021:Go 6976; C083832:N,N-dipropyl-2-(4-methoxy-3-(2-phenylethoxy)phenyl)ethylamine monohydrochloride; D018698:Glutamic Acid; D011493:Protein Kinase C; C050232:1,3-ditolylguanidine; D002118:Calcium; C065310:igmesine