title: Effects of insulin-like growth factor 1 on voltage-gated ion channels in cultured rat hippocampal neurons.
abstract: Insulin-like growth factor 1 (IGF-1) has important functions in the brain, including metabolic, neurotrophic, neuromodulatory, and neuroendocrine actions, and it is also prevents amyloid beta-induced death of hippocampal neurons. However, its functions on the voltage-gated ion channels in hippocampus remain uncertain. In the present study, we investigated the effects of IGF-1 on voltage-gated potassium, sodium, and calcium channels in the cultured rat hippocampal neurons using the whole-cell patch clamp recordings. Following incubation with different doses of IGF-1 for 24 h, a block of the peak transient A-type K+ currents amplitude (IC50: 4.425 ng/ml, Hill coefficient: 0.621) was observed. In addition, after the application of IGF-1, the amplitude of high-voltage activated Ca2+ currents significantly increased but activation kinetics did not significantly alter (V1/2: -33.45 +/- 1.32 mV, k = 6.16 +/- 1.05) compared to control conditions (V1/2: -33.19 +/- 2.28 mV, k = 7.26 +/- 1.71). However, the amplitude of Na+, K+, and low-voltage activated Ca2+ currents was not affected by the application of IGF-1. These data suggest that IGF-1 inhibits transient A-type K+ currents and enhances high-voltage-activated Ca2+ currents, but has no effects on Na+ and low-voltage-activated Ca2+ currents.
authors.affiliation: Institute of Cerebrovascular Diseases, Xuanwu Hospital, The Capital University of Medical Sciences, Beijing 100053, China. xch02@sina.com
authors.forename: Changhong
authors.initials: C
authors.lastname: Xing
authors.forename: Yanling
authors.initials: Y
authors.lastname: Yin
authors.forename: Xiangping
authors.initials: X
authors.lastname: He
authors.forename: Zuoping
authors.initials: Z
authors.lastname: Xie
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology
chemical_list: D024642:Potassium Channels, Voltage-Gated; D015222:Sodium Channels; D007334:Insulin-Like Growth Factor I