Development of multiple calcium channel types in cultured mouse hippocampal neurons

• Published in: Neuroscience 1999-05, Vol.90 (2), p.383-388
• Main Authors: Chameau, P, Lucas, P, Melliti, K, Bournaud, R, Shimahara, T
• Format: Article
• Language: English
• Subjects: Amiloride; Amiloride - pharmacology; Animals; Biological and medical sciences; Calcium Channel Blockers; Calcium Channel Blockers - pharmacology; Calcium Channels; Calcium Channels - biosynthesis; Calcium Channels - drug effects; Calcium Channels - physiology; calcium current; Cell Aging; Cells, Cultured; Cellular Senescence; Central nervous system; development; Electrophysiology; Embryo, Mammalian; Fetus; Fundamental and applied biological sciences. Psychology; hippocampal neurons; Hippocampus; Hippocampus - cytology; Hippocampus - physiology; Life Sciences; Membrane Potentials; Membrane Potentials - drug effects; Mice; Neurons; Neurons - cytology; Neurons - drug effects; Neurons - physiology; Neurons and Cognition; nifedipine; omega-Agatoxin IVA; omega-Conotoxin GVIA; Patch-Clamp Techniques; Peptides; Peptides - pharmacology; Pyramidal Cells; Pyramidal Cells - cytology; Pyramidal Cells - drug effects; Pyramidal Cells - physiology; Spider Venoms; Spider Venoms - pharmacology; Time Factors; Vertebrates: nervous system and sense organs; ω-Agatoxin IVA; ω-conotoxin GVIA
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(98)00457-6

The development of multiple calcium channel activities was studied in mouse hippocampal neurons in culture, using the patch-clamp technique. A depolarizing pulse (40–50 ms duration) from the holding potential of −80 mV to levels more depolarized than −40 mV produced a low threshold T-type current. The T-type current was observed in 52% of four days in vitro neurons. The number of neurons which expressed T-type current decreased with age of culture, so that the current was detected in only 18% of neurons after 16 days in vitro. The T-type current densities varied between 1.9 pA/pF and 3.29 pA/pF in the mean values during the period studied (4–16 days in vitro). A depolarizing pulse from −80 mV to levels more depolarized than −35 mV evoked a high threshold calcium channel current. The high threshold current density increased in the mean values from 3.9 pA/pF in four days in vitro neurons to 28 pA/pF in 16 days in vitro neurons. We have then examined the effect of nifedipine, ω-Agatoxin IVA and ω-conotoxin GVIA on the high threshold current. Nifedipine (1–5 μM) sensitive current density stayed in the range of 1.9–2.1 pA/pF during 4–16 days in vitro, while ω-Agatoxin IVA (200 nM) sensitive current density increased in the mean values from 1.54 pA/pF in four days in vitro neurons to 21.5 pA/pF in 16 days in vitro neurons. The ω-conotoxin GVIA sensitive N-type channel current was maximum at eight days in vitro (5.44 pA/pF) and it reduced progressively to reach almost half (2.46 pA/pF) in 16 days in vitro neurons. These results showed that diverse subtypes of calcium channels change in density during the early period of culture. We suggest that the temporal expression of each type of channel may be linked to the development of neural activities.