Intracellular calcium store filling by an L-type calcium current in the basolateral amygdala at subthreshold membrane potentials.
The long-term changes that underlie learning and memory are activated by rises in intracellular Ca2+ that activate a number of signalling pathways and trigger changes in gene transcription. Ca2+ rises due to influx via L-type voltage-dependent Ca2+ channels (L-VDCCs) and release from intracellular Ca2+ stores have been consistently implicated in the biochemical cascades that underlie the final changes in memory formation. Here, we show that pyramidal neurones in the basolateral amygdala express an L-VDCC that is active at resting membrane potentials. Subthreshold depolarization of neurones either by current injection or summating synaptic potentials led to a sustained rise in cytosolic Ca2+ that was blocked by the dihydropyridine nicardipine. Activation of metabotropic receptors released Ca2+ from intracellular Ca2+ stores. At hyperpolarized potentials, metabotropic-evoked store release ran down with repeated stimulation. Depolarization of cells to -50 mV, or maintaining them at the resting membrane potential, restored release from intracellular Ca2+ stores, an effect that was blocked by nicardipine. These results show that Ca2+ influx via a low-voltage-activated L-type Ca2+ current refills inositol 1,4,5-trisphosphate (IP(3))-sensitive intracellular Ca2+ stores, and maintains Ca2+ release and wave generation by metabotropic receptor activation.
Power
John M
JM
Queensland Brain Institute, School of Biomedical Sciences, St Lucia, Queensland 4072, Australia.
Sah
Pankaj
P
D000465:Algorithms; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D015544:Inositol 1,4,5-Trisphosphate; D020866:omega-Conotoxin GVIA; D002118:Calcium