Neurite promoting activity of insulin, insulin-like growth factor I and nerve growth factor on spinal motoneurons is astrocyte dependent.
Mouse motoneurons were isolated from dissociated E15 mouse spinal cord and grown on polyornithine-coated round coverslips in a growth medium (DMEM/F12) supplemented with progesterone, trans-ferrin, selenium, horse serum and muscle extract. Astrocytes from newborn mouse neopallium were grown on rectangular coverslips. The motoneuron neurite growth was determined at day 8 of culture by counting, using the light microscope, the intersections produced by neurites radiating from the perikaryon placed centrally in a graticule eyepiece of concentric circles. The mean intersections for cultures without addition of astrocytes, insulin, insulin-like growth factor I (IGF-I) or nerve growth factor (NGF) was 12.6 +/- 0.8. When astrocytes on a separate coverslip were introduced from day 1, there was a small increase in neurite growth (16.3 +/- 0.9). The neurite growth was further increased significantly with the addition of insulin (27.3 +/- 1.4), IGF-I (31.5 +/- 1.4) or NGF (21.8 +/- 1.1) to cultures with astrocytes. Insulin, IGF-I or NGF in the absence of astrocytes did not greatly increase the neurite growth. We conclude that insulin, IGF-I and NGF promote neurite growth through some interactions with astrocytes.
Ang
L C
LC
Department of Pathology (Neuropathology), University of Saskatchewan, Saskatoon, Canada.
Bhaumick
B
B
Juurlink
B H
BH
D000818:Animals; D001253:Astrocytes / Q000502:physiology; D002478:Cells, Cultured; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051379:Mice; D009046:Motor Neurons / Q000187:drug effects*; D009414:Nerve Growth Factors / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects*; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*
D007328:Insulin; D009414:Nerve Growth Factors; D007334:Insulin-Like Growth Factor I