Cadmium rapidly and irreversibly blocks presynaptic phospholipase C-linked metabotropic glutamate receptors. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Neurochemistry International Année : 1996

Cadmium rapidly and irreversibly blocks presynaptic phospholipase C-linked metabotropic glutamate receptors.

Résumé

Calcium ions (Cd2+) inhibit inositol phosphate (IP) formation elicited by glutamate (GLU) or K+ ions, without affecting carbachol (Carb)-induced IP response in 8-day-old rat forebrain synaptoneurosomes and synaptosomes. On the contrary, Cd2+ was almost ineffective in blocking GLU- and K(+)-responses in hippocampal neurones in culture. The mechanism of Cd2+ inhibition was thus examined in synaptoneurosomes. Extensive washing of synaptoneurosomes pretreated for 1, 5, 15, or 30 min by 100 microM Cd2+ did not modify the inhibitory effect of Cd2+ on GLU-, K(+)- and A23187-evoked IP formation or its lack of effect on Carb response. The later addition of a high affinity Cd2+ chelator (100 microM), N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) also did not reverse the inhibitory effect. TPEN, however, penetrates into synaptoneurosomes and efficiently displaces Cd2+ from the Fura-2-Cd2+ complex as shown by Fura-2 fluorescence recordings. TPEN is not easily removed from the intracellular space, as demonstrated by its ability to still block Cd(2+)-induced Fura-2 fluorescence increase after extensive washing. Pretreatment of synaptoneurosomes by this chelator did not prevent Cd2+ inhibition of GLU-induced IP formation. These data indicate that Cd2+ ions rapidly, irreversibly and extracellularly inhibit GLU-elicited IP formation in synaptoneurosomes or synaptosomes, but not in hippocampal neurones in culture. It is speculated that Cd2+ ions could allow one to distinguish the activity of presynaptic metabotropic glutamate receptors (mGLURs) linked to phosphoinositide metabolism from that of mGLURs located postsynaptically.

Dates et versions

hal-00397709 , version 1 (23-06-2009)

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Citer

Michel Vignes, Emmanuelle M. Blanc, Frédérique Davos, Janique Guiramand, Max Récasens. Cadmium rapidly and irreversibly blocks presynaptic phospholipase C-linked metabotropic glutamate receptors.. Neurochemistry International, 1996, 29 (4), pp.371-81. ⟨10.1016/0197-0186(96)00008-3⟩. ⟨hal-00397709⟩
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