Q‐ and L‐type calcium channels control the development of calbindin phenotype in hippocampal pyramidal neurons in vitro

Abstract

Cultured immature hippocampal neurons from embryonic 17-day-old rats were used to explore activity-dependent regulation of neuronal phenotype differentiation in the developing hippocampus. The calbindin-D28k phenotype of the pyramidal neurons appeared during the first 6 days in culture, and was expressed by 12% of the cells on day 6. Daily stimulation with 50 mM KCl during the first 5 days in vitro increased the number of calbindin-D28k-positive pyramidal neurons without affecting neuronal survival. This effect was prevented by buffering extracellular Ca2+. Omega-agatoxin-IVA-sensitive Q-type and nitrendipine-sensitive L-type voltage-gated Ca2+ channels (VGCCs) carried Ca2+ currents and Ca2+ influx in immature pyramidal neurons at somata level. Blockade of these channels inhibited calbindin-D28k phenotype induced by 50 mM KCl. Conversely, glutamate-activated Ca2+ channel antagonists did not affect the KCl-induced calbindin-D28k phenotype. Chronic blockade of Q- and/or L-type VGCCs downregulated the normal calbindin-D28k development of immature pyramidal neurons without affecting neuronal survival, the somatic area of pyramidal neurons or the number of GABAergic-positive (gamma-aminobutyric acid) interneurons. However, at later developmental stages, Q-type VGCCs lost their ability to control Ca2+ influx at somata level, and both Q- and L-type VGCCs failed to regulate calbindin-D28k phenotype. These results suggest that Q-type channels, which have been predominantly associated with neurotransmitter release in adult brain, transiently act in synergy with L-type VGCCs to direct early neuronal differentiation of hippocampal pyramidal neurons before the establishment of their synaptic circuits.

Ion Channel Development, Spontaneous Activity, and Activity-Dependent Development in Nerve and Muscle Cells

“…Ca 2ϩ release mechanisms show rapid and regionalized developmental changes (166), and developmental changes in both Ca 2ϩ release mechanisms and Ca 2ϩ buffering molecules are influenced by activity (69,398).…”

The Ascidian Dihydropyridine-Resistant Calcium Channel as the Prototype of Chordate L-Type Calcium Channel

“…Cell migration and neurite extension also require activities of L-type class Cav channel. However, such 'slow' roles of Cav channel are not exclusive to Ltype Cav channels but also seen in non-L-type Cav channels [7].…”

Spontaneous glutamate release controls NT‐3‐dependent development of hippocampal calbindin–D28k phenotype through activation of sodium channels ex vivo

“…Embryonic glutamatergic pyramidal neurons of the rat hippocampus generate spontaneous phasic TTX‐sensitive action potentials (ESAPs) that in turn regulate the calbindin–D 28k phenotype in vitro (Boukhaddaoui et al ., 2000; Boukhaddaoui et al ., 2001). In order to address whether the present described glutamate pathway regulates ESAPs, spontaneous electrical activity was recorded in single‐cell and very low density culture of E17 pyramidal hippocampal neurons after 3–6 DIV.…”

“…Concomitantly, pyramidal neurons generate spontaneous phasic sodium‐driven action potentials (referred to as early spontaneous action potentials, i.e. ESAPs) that regulate the acquisition of their calbindin–D 28k phenotype (Boukhaddaoui et al ., 2000; Boukhaddaoui et al ., 2001). From these studies, questions arise concerning the possible functional links between these molecules as well as the exact mechanisms that control this activity‐dependent NT‐3 autocrine loop.…”