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Chronic NMDA receptor antagonism during retinotopic map formation depresses CaM kinase II differentiation in rat
A J Scheetz1, G T Prusky, M Constantine-Paton
1Yale University, Department of Biology, New Haven, CT 06520, USA.
Abstract:
We examined the effects of chronic NMDA receptor antagonism on the normal postnatal differentiation of calcium- and calmodulin-dependent kinase II (CaM kinase II) in the rat superior colliculus. At postnatal day (P) zero, most CaM kinase II protein, as well as CaM kinase II activity, was detected in the soluble fraction. In vitro phosphorylation of P0 superior colliculus revealed several prominent substrates in both the particulate and soluble fractions. At P19 there was more particulate enzyme than soluble enzyme, and CaM kinase II activity in the particulate fraction was higher than in P0 particulate tissue. Additionally, in vitro phosphorylation of P19 superior colliculus revealed many more CaM kinase II substrates. Chronic NMDA receptor antagonism with 2-amino-5-phosphonovalerate (DL-AP5) caused CaM kinase II to retain many of the characteristics of the enzyme found in P0 untreated superior colliculus. In P19 superior colliculus treated with LD-AP5 from birth, most of the protein was in the soluble fraction, CaM kinase II activity was largely restricted to the soluble fraction, and only a few substrates were observed by in vitro phosphorylation. These effects were not observed in tissue treated with the inactive isomer, L-AP5. These results suggest that synaptic maturation is slowed by antagonism of NMDA receptors during retinotopic map formation.
Insights
NMDA receptor antagonism slows synaptic maturation by altering CaM kinase II differentiation in developing rat brains. This impacts normal postnatal development of the superior colliculus.
Area of Science:
- Neuroscience
- Developmental Biology
- Biochemistry
Background:
- Calcium- and calmodulin-dependent kinase II (CaM kinase II) plays a crucial role in synaptic plasticity and neuronal development.
- NMDA receptors are critical for synaptic maturation and the formation of neural circuits, including retinotopic maps.
Purpose of the Study:
- To investigate the impact of chronic NMDA receptor antagonism on the postnatal differentiation of CaM kinase II in the rat superior colliculus.
- To elucidate how NMDA receptor activity influences the developmental changes in CaM kinase II localization, activity, and substrate phosphorylation.
Main Methods:
- Utilized chronic NMDA receptor antagonism with 2-amino-5-phosphonovalerate (DL-AP5) in developing rats from postnatal day zero.
- Analyzed CaM kinase II protein levels, activity, and substrate phosphorylation in soluble and particulate fractions of the superior colliculus at different postnatal ages (P0 and P19).
- Compared the effects of the active NMDA antagonist (DL-AP5) with its inactive isomer (L-AP5).
Main Results:
- In untreated rats, CaM kinase II shifted from a predominantly soluble form at P0 to a more particulate form at P19, with increased activity and more substrates.
- Chronic NMDA receptor antagonism with DL-AP5 at P19 resulted in CaM kinase II remaining largely soluble, with reduced activity and fewer substrates, mimicking the P0 state.
- These effects were specific to the active NMDA antagonist, as L-AP5 showed no significant impact.
Conclusions:
- NMDA receptor activity is essential for the normal postnatal differentiation and maturation of CaM kinase II in the rat superior colliculus.
- Antagonism of NMDA receptors during retinotopic map formation significantly delays synaptic maturation processes.
- These findings highlight the critical role of NMDA receptor-mediated signaling in the developmental trajectory of key synaptic proteins.