 |
||||
|
||||
|
||||
|
||||
The Journal of Neuroscience, December 3, 2003, 23(35)
Previous Article | Next Article
This Week in the Journal
Cellular/Molecular
A Calcium-Dependent Synaptic Glue?
Ca2+ Dependency of N-Cadherin Function Probed by Laser Tweezer and Atomic Force Microscopy
Werner Baumgartner, Nikola Golenhofen, Niko Grundhöfer, Johannes Wiegand, and Detlev Drenckhahn
(see pages 11008-11014)
Changes in the shape and size of synapses are perhaps the ultimate expression of neuronal plasticity. This week, Baumgartner et al. provide evidence that N-cadherin acts as a sort of "synaptic glue," the stickiness of which is controlled by physiological fluctuations in intracellular as well as extracellular calcium. The authors report that rapid activity-dependent decreases in extracellular calcium temporarily release N-cadherin molecules from their homophilic partners. They measured calcium-dependent binding among cadherin dimers between a plate and a cantilever tip using atomic force microscopy, akin to pressing your finger against a surface rubbed with a glue-stick. Increases in intracellular calcium also altered N-cadherin adhesion as measured by laser tweezer-induced trapping of N-cadherin-coated beads stuck to PC12 cells. The latter action presumably occurred because of calcium-dependent dissociation of N-cadherin from the actin cytoskeleton. The making and breaking of N-cadherin contacts may allow the adhesion molecule to relocate to the synaptic periphery, leaving more room for synaptic molecules and allowing remodeling and expansion of synaptic active zones.
Development/Plasticity/Repair
The Benefits of an Enriched Environment
Enriched Environment Confers Resistance to 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine and Cocaine: Involvement of Dopamine Transporter and Trophic Factors
Erwan Bezard, Sandra Dovero, David Belin, Sophie Duconger, Vernice Jackson-Lewis, Serge Przedborski, Pier Vincenzo Piazza, Christian E. Gross, and Mohamed Jaber
(see pages 10999-11007)
It would be nice to think that a stimulating, active existence could modify or prevent neurological maladies such as drug addiction or Parkinson's disease (PD). Bezard et al. show this week that mice maintained in an enriched environment (EE) for 2 months seem to undergo protective downregulation of dopamine transporters (DAT), which the authors aptly describe as the "neural gate" to dopamine neurotoxins. EE-raised mice were less sensitive to cocaine and were dramatically resistant to the PD-inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The EE mice lost substantially fewer neurons after MPTP treatment than mice in the standard (boring?) environment. The actions of cocaine and MPTP depend on the function of dopamine transporters. Accordingly, in situ hybridization revealed reduced DAT expression throughout the dopaminergic striatum of EE mice. Interestingly, EE mice had slightly fewer dopamine neurons in the substantia nigra pars compacta before drug treatment, perhaps reflecting differential neuronal development or migration. What specifically constitutes an enriched environment? In this case, it was a bigger cage, half a dozen toys, and a running wheel. Other recent work suggests that physical exercise may also serve in a similar manner. Overall, it's murine evidence for a use it or lose it philosophy.
Behavioral/Systems/Cognitive
Primary Motor Cortex and Early Skill Learning
Early Skill Learning Is Expressed through Selection and Tuning of Cortically Represented Muscle Synergies
William J. Kargo and Douglas A. Nitz
(see pages 11255-11269)
Coordinated muscle movements can be combined in patterns to achieve complex motor skills. How this learning process occurs over time is not entirely clear, but it is thought that mental "building blocks" are important CNS components of skill acquisition. One type of building block is termed a synergy, a grouping of activated muscles presumably formed through coordinated use. Individual synergies can be combined and scaled appropriately to suit the newly learned task. Another type of block is the motor pattern, which is formed when synergies are combined or repeated over time. Where and how in the CNS these blocks are constructed into complex motor skills is not clear, but primary motor cortex (M1) seems a good starting point. In this week's Journal, Kargo and Nitz recorded from M1 neurons and muscle cells during early skill learning in rats. They found that the rats made significant progress in learning a reach-to-grasp task on the first day, followed by a second phase of learning over several days. During early learning, the rats improved their task performance by both selecting appropriate building blocks and then properly weighting them to achieve the task. These adaptations were reflected in the firing rates of M1 neurons.
This Article Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager 
Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content
|
|
|
|
 |
|