The overall objective of this research proposal is to determine if the free radical gas nitric oxide (NO) plays a critical role in synaptic pattern formation in the central nervous system. An emerging hypothesis predicts that NO serves as a retrograde messenger to initiate, strengthen, or stabilize developing synapses on nitric oxide synthase (NOS) containing neurons. The hypothesis predicts that NO release from post-synaptic neurons activates a guanylate cyclase mechanism in presynaptic axons to enhance neurotransmitter release. A further prediction is that NO release is produced by NMDA-receptor (NMDAr) mediated calcium influx which activates NOS. To investigate these hypothesizes the investigator proposed to use the development of the retino-tectal pathway and the patch-cluster system in the rat superior colliculus (SC) as a model system. Anatomical, electrophysiological, and calcium imaging techniques will be used to investigate five specific aims. (1) Determine if there is a temporal correlation between the expression of NOS and the NMDA receptor and the growth and refinement of axons in the SC. This will be tested using antibody immunocytochemistry and anterograde labeling techniques. (2) Determine if inhibition of NOS or blockade of the NMDA receptor alter the growth of these axons. Pharmacological agents will be used to block NOS and NMDAr and anterograde tracers will be used to examine alterations in axon distribution. An nNOS knockout mouse will also be used to test this hypothesis. (3) Determine when the synapses onto the NOS neurons become functional and if NMDA channel currents are involved. The applicant will also determine whether synaptic transmission or the membrane properties of NOS cells are affected by NO production or NOS inhibition. These studies will use electrophysiological techniques in isolated brainstem and brain slice preparations, including tissue from nNOS knockout mouse. (4) Determine if NOS-neurons have NMDAr-mediated [Ca2+]i increases or show elevated [Ca2+]i resting levels during periods of synaptic development. This will be determined using calcium imaging techniques. (5) Determine if NO has a role in modulating the calcium transients induced by NMDA and other agonists. Calcium imaging and pharmacological manipulations of NO will be used in these studies. Collectively, these studies should provide important new information concerning the mechanisms underlying the role of NO in synaptic plasticity and development.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS036000-03
Application #
2858207
Study Section
Neurology B Subcommittee 2 (NEUB)
Program Officer
Chiu, Arlene Y
Project Start
1997-01-01
Project End
2000-12-31
Budget Start
1999-01-01
Budget End
2000-12-31
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Louisiana State University Hsc New Orleans
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
782627814
City
New Orleans
State
LA
Country
United States
Zip Code
70112
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Mize, R Ranney; Graham, Sean K; Cork, R John (2002) Expression of the L-type calcium channel in the developing mouse visual system by use of immunocytochemistry. Brain Res Dev Brain Res 136:185-95
Scheiner, C A; Kratz, K E; Guido, W et al. (2001) Prenatal and postnatal expression of nitric oxide in the developing kitten superior colliculus revealed with NADPH diaphorase histochemistry. Vis Neurosci 18:43-54
Lo, F S; Mize, R R (2000) Synaptic regulation of L-type Ca(2+) channel activity and long-term depression during refinement of the retinocollicular pathway in developing rodent superior colliculus. J Neurosci 20:RC58
Mize, R R; Butler, G D (2000) The NMDAR1 subunit of the N-methyl-D-aspartate receptor is localized at postsynaptic sites opposite both retinal and cortical terminals in the cat superior colliculus. Vis Neurosci 17:41-53
Wu, H H; Cork, R J; Huang, P L et al. (2000) Refinement of the ipsilateral retinocollicular projection is disrupted in double endothelial and neuronal nitric oxide synthase gene knockout mice. Brain Res Dev Brain Res 120:105-11
Mize, R R; Lo, F (2000) Nitric oxide, impulse activity, and neurotrophins in visual system development(1). Brain Res 886:15-32
Wu, H H; Cork, R J; Mize, R R (2000) Normal development of the ipsilateral retinocollicular pathway and its disruption in double endothelial and neuronal nitric oxide synthase gene knockout mice. J Comp Neurol 426:651-65
Cork, R J; Calhoun, T; Perrone, M et al. (2000) Postnatal development of nitric oxide synthase expression in the mouse superior colliculus. J Comp Neurol 427:581-92
Scheiner, C A; Cork, R J; Mize, R R (1999) Failure to disrupt development of cholinergic fiber patches in the superior colliculus in nitric oxide synthase deficient mice. Brain Res Dev Brain Res 118:217-20

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