Glutamate-induced changes in the pattern of hippocampal dendrite outgrowth: A role for calcium-dependent pathways and the microtubule cytoskeleton
✍ Scribed by Wilson, Mark T. ;Kisaalita, William S. ;Keith, Charles H.
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 190 KB
- Volume
- 43
- Category
- Article
- ISSN
- 0022-3034
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✦ Synopsis
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 glutamateinduced 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 activitydependent regulation of dendrite morphology during development and after pathology.