Spatial distribution of calcium channels and cytosolic calcium transients in growth cones and cell bodies of sympathetic neurons.
AUTOR(ES)
Lipscombe, D
RESUMO
Ca2+ imaging and single-channel recording were used to study the regulation of cytosolic free Ca2+ ([Ca2+]i) in local regions of frog sympathetic neurons. Digital imaging with the fluorescent Ca2+ indicator fura-2 demonstrated: (i) resting [Ca2+]i of 70-100 nM; (ii) significant increases in [Ca2+]i in growth cones and cell bodies following depolarization induced by extracellular electrical stimulation or increased external K+; (iii) in cell bodies, large transient increases in [Ca2+]i following exposure to caffeine and sustained oscillations in [Ca2+]i in the presence of elevated K+ and caffeine; and (iv) in growth cones, smaller and briefer changes in [Ca2+]i in response to caffeine. The nature of the depolarization-induced Ca2+ entry was studied with cell-attached patch recordings (110 mM Ba2+ in recording pipette). Ca2+ channel activity was observed in 18 of 20 patches on cell bodies, 3 of 5 patches along neurites, and 36 of 41 patch recordings from growth cones. We observed two types of Ca2+ channels: L-type channels, characterized by a 28-pS slope conductance, sensitivity to dihydropyridine Ca2+ channel agonist, and availability even with depolarizing holding potentials; and N-type channels, characterized by a 15-pS slope conductance, resistance to dihydropyridines, and inactivation with depolarized holding potentials. Both types of channels were found on growth cones and along neurites as well as on cell bodies; channels often appeared concentrated in local hot spots, sometimes dominated by one channel type.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=280000Documentos Relacionados
- Single calcium channels in rat and guinea-pig hippocampal neurons.
- Mechanisms of GABA and glycine depolarization-induced calcium transients in rat dorsal horn neurons.
- Ultrastructural networks in growth cones and neurites of cultured central nervous system neurons.
- Effects of temperature on calcium current of bullfrog sympathetic neurons.
- Calcium-dependent chloride current induced by axotomy in rat sympathetic neurons.