title: Glutamate-induced changes in the pattern of hippocampal dendrite outgrowth: a role for calcium-dependent pathways and the microtubule cytoskeleton.
abstract: Glutamate regulation of a variety of aspects of dendrite development may be involved in neuronal plasticity and neuropathology. In this study, we examine the calcium-dependent pathways and alterations in the microtubule (MT) cytoskeleton that may mediate glutamate-induced changes in the pattern of dendrite outgrowth. We used Fura-2 AM and inhibitors of the calcium-dependent proteins, calmodulin and calpain, to identify the role of specific calcium-dependent pathways in glutamate-regulated dendrite outgrowth. Additionally, we used a quantitative fluorescence technique to correlate changes in MT levels with glutamate-induced changes in dendrite outgrowth. We show that the intracellular calcium concentration ([Ca(2+)](i)) changes in a biphasic manner over a 12-h period in the presence of glutamate. A transient increase in [Ca(2+)](i) over the first hour of glutamate exposure correlated with a calmodulin-associated increase in the rate of dendrite outgrowth, whereas a sustained increase in [Ca(2+)](i) was correlated with calpain-associated dendrite retraction. Quantitative fluorescence measurements showed no net change in the level of MTs during calmodulin-associated increases in dendrite outgrowth, but showed a significant decline in the level of MTs during calpain-associated dendrite retraction. These findings provide insights into the intracellular mechanisms involved in activity-dependent regulation of dendrite morphology during development and after pathology.
authors.affiliation: BD Transduction Laboratories, Lexington, Kentucky 40503, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Wilson
authors.forename: W S
authors.initials: WS
authors.lastname: Kisaalita
authors.forename: C H
authors.initials: CH
authors.lastname: Keith
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D003712:Dendrites / Q000187:drug effects / Q000378:metabolism*; D004151:Dipeptides / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005452:Fluoresceins; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D006023:Glycoproteins / Q000494:pharmacology; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008868:Microtubule Proteins / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D004791:Enzyme Inhibitors; D005452:Fluoresceins; D006023:Glycoproteins; D007093:Imidazoles; D008868:Microtubule Proteins; C039304:calpain inhibitors; D018698:Glutamic Acid; C031938:calmidazolium; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D017239:Paclitaxel; D015739:Nocodazole; D002118:Calcium; C058076:calpain inhibitor III