The goal of the research proposed is to understand, at the level of individual cells and fibers, the substrate of the functional reorganization that follows neonatal deafferentation of the hamster's superior colliculus (SC). The particular experiments outlined in this application are designed to examine three aspects of the collicular reorganization that occurs after neonatal enucleation of one eye. These are: 1. Reorganization of the axon arbors of individual, functionally characterized retinal and subcortical somatosensory afferents, 2. Effects of deafferentation upon structure-function relationships for postsynaptic cells, and 3. The role which sprouting of noradrenergic (NA) afferents plays in deafferentation induced functional reorganization. Extracellular recording studies have already shown that neonatal enucleation markedly alters the response properties of many SC neurons and """"""""bulk tracing"""""""" experiments have demonstrated further that part of this reorganization might be explained by alterations in the terminal fields of several of the residual projections to the tectum. We will use intra-axonal recording and horseradish peroxidase (HRP) injection techniques to determine whether the expansion of the remaining retinal and subcortical somatosensory inputs to the SC reflects collateral sprouting; i.e., increases in the arbors of individual axons, """"""""spreading"""""""" of azon terminals, i.e., an increase in the extent of the terminal arbors of a given axon will a concomitant decrease in their density or reduced overlap of normally sized arbors from different axons. We will also employ intracellular recording and HRP injection to define the receptive fields and structure of postsynaptic cells in the deafferented SC. A number of morphological studies have suggested that changes in the dendritic architecture of partially deafferented neurons may also play an important role in functional reorganization. Our experiments will test this hypothesis directly at the level of individual cells. In a third set of experiments, we will examine the role that sprouting of NA axons plays in the physiological changes observed in the deafferented SC. Our previous studies have demonstrated that NA fibers sprout vigorously after neonatal enucleation and our working hypothesis is that these afferents may act to inhibit the expression of weak sensory inputs onto SC neurons.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY004170-07
Application #
3258688
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1979-07-01
Project End
1992-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
7
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Type
Schools of Osteopathy
DUNS #
City
Stratford
State
NJ
Country
United States
Zip Code
08084
Lane, R D; Allan, D M; Bennett-Clarke, C A et al. (1997) Projection status of calbindin- and parvalbumin-immunoreactive neurons in the superficial layers of the rat's superior colliculus. Vis Neurosci 14:277-86
Lane, R D; Allan, D M; Bennett-Clarke, C A et al. (1996) Differential age-dependent effects of retinal deafferentation upon calbindin- and parvalbumin-immunoreactive neurons in the superficial layers of the rat's superior colliculus. Brain Res 740:208-14
Mooney, R D; Huang, X; Shi, M Y et al. (1996) Serotonin modulates retinotectal and corticotectal convergence in the superior colliculus. Prog Brain Res 112:57-69
Arce, E A; Bennett-Clarke, C A; Rhoades, R W (1994) Ultrastructural organization of the noradrenergic innervation of the superficial gray layer of the hamster's superior colliculus. Synapse 18:46-54
Mooney, R D; Zhang, Y; Rhoades, R W (1994) Effects of angiotensin II on visual neurons in the superficial laminae of the hamster's superior colliculus. Vis Neurosci 11:1163-73
Mooney, R D; Shi, M Y; Rhoades, R W (1994) Modulation of retinotectal transmission by presynaptic 5-HT1B receptors in the superior colliculus of the adult hamster. J Neurophysiol 72:3-13
Huang, X; Mooney, R D; Rhoades, R W (1993) Effects of serotonin on retinotectal-, corticotectal-, and glutamate-induced activity in the superior colliculus of the hamster. J Neurophysiol 70:723-32
Mooney, R D; Rhoades, R W (1993) Determinants of axonal and dendritic structure in the superior colliculus. Prog Brain Res 95:57-67
Rhoades, R W; Bennett-Clarke, C A; Lane, R D et al. (1993) Increased serotoninergic innervation of the hamster's superior colliculus alters retinotectal projections. J Comp Neurol 334:397-409
Mooney, R D; Nikoletseas, M M; King, T D et al. (1993) Correlations between the receptive field properties and morphology of neurons in the deep layers of the hamster's superior colliculus. J Comp Neurol 335:214-27

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