Imaging of calcium variations in living dendritic spines of cultured rat hippocampal neurons.
1. Cultured rat hippocampal neurons were loaded with the Ca2+ indicator fura-2 through micropipettes and visualized with an inverted microscope equipped with a high power objective and a cooled CCD camera. The responses of dendritic spines and their parent dendrites to stimuli which evoke a rise of [Ca2+]i were monitored. 2. NMDA caused a rapid and transient rise in [Ca2+]i, which was more evident in the spine than in the parent dendrite. The recovery in both compartments had the same time course, and was dependent on normal [Na+]o. 3. Application of alpha-latrotoxin, which causes release of neurotransmitters from terminals, produced a rise of [Ca2+]i in the dendritic spines, more than in their parent dendrites. Prolonged exposure to the drug eliminated the spine/dendrite disparity. 4. The presence of voltage-gated calcium channels in dendritic spines is indicated by the enhanced calcium rise in spines rather than dendrites of cells depolarized by either intracellular current injection or by raising [K+]o. This rise was attenuated by nifedipine or verapamil, both L-type channel blockers. 5. It is suggested that the dendritic spine constitutes an independent calcium compartment that is closely linked to the parent dendrite.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism*; D004594:Electrophysiology; D005453:Fluorescence; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D013111:Spider Venoms / Q000494:pharmacology
D015220:Calcium Channels; C546387:P2ry2 protein, rat; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D013111:Spider Venoms; D016202:N-Methylaspartate; C020763:alpha-latrotoxin; D002118:Calcium