The long-range objective of this research is to understand how innervation regulates the number and distribution of nicotinic acetylcholine receptors (AChRs) on neurons. Our approach has been to use a simple and tractable system, the frog cardiac ganglion, where AChRs on parasympathetic neurons can be analyzed by immunocytochemistry, autoradiography, and biochemistry, and where the influence of innervation upon AChRs can be monitored during denervation and reinnervation in adult frogs (Rana) as well during initial innervation in embryos (Xenopus). In the past award period we found that denervation does not increase the number of AChRs on the surface of cardiac ganglion cells, measured by the binding of 125I-neuronal bungarotoxin, a snake toxin that blocks AChR function. Denervation does increase the sensitivity of cardiac ganglion cells to acetylcholine (ACh) applied via a micropipet; this effect appears to be due to a reduction in the effectiveness of the hydrolytic enzyme acetylcholinesterase (AChE) and not to a change in the number of functional AChRs on the cell surface. We have three specific aims. In the first, we will examine the consequences of denervation and reinnervation upon the distribution of AChRs and AChR clusters in adult Rana pipiens. In the second aim, we will determine whether denervation supersensitivity can be explained by a reduction in the number of AChE molecules in the extracellular space surrounding ganglion cells and/or a change in their kinetic properties. We will also examine whether the reduction in ACh sensitivity that occurs during the first stages of reinnervation is due to a change in AChE, in AChRs, or in both. In the third aim we will examine whether AChRs are expressed on developing cardiac ganglion cells in Xenopus laevis before, during, or after cells are contacted by preganglionic axons. We will determine whether AChRs appear on neurons that have never been innervated by preganglionic axons, and, if so, whether innervation enhances AChR expression. These studies should increase our understanding of how neuronal nicotinic AChRs and ACh sensitivity are regulated by innervation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS024207-09
Application #
3408527
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1988-07-01
Project End
1996-03-31
Budget Start
1993-04-01
Budget End
1994-03-31
Support Year
9
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Dentistry
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Rogers, Marc; Sargent, Peter B (2003) Rapid activation of presynaptic nicotinic acetylcholine receptors by nerve-released transmitter. Eur J Neurosci 18:2946-56
Dourado, Michelle; Sargent, Peter B (2002) Properties of nicotinic receptors underlying Renshaw cell excitation by alpha-motor neurons in neonatal rat spinal cord. J Neurophysiol 87:3117-25
Nguyen, Don; Sargent, Peter B (2002) Synaptic vesicle recycling at two classes of release sites in giant nerve terminals of the embryonic chicken ciliary ganglion. J Comp Neurol 448:128-37
Ullian, E M; McIntosh, J M; Sargent, P B (1997) Rapid synaptic transmission in the avian ciliary ganglion is mediated by two distinct classes of nicotinic receptors. J Neurosci 17:7210-9
Horch, H L; Sargent, P B (1996) Effects of denervation on acetylcholine receptor clusters on frog cardiac ganglion neurons as revealed by quantitative laser scanning confocal microscopy. J Neurosci 16:1720-9
Wilson Horch, H L; Sargent, P B (1996) Synaptic and extrasynaptic distribution of two distinct populations of nicotinic acetylcholine receptor clusters in the frog cardiac ganglion. J Neurocytol 25:67-77
Sargent, P B; Garrett, E N (1995) The characterization of alpha-bungarotoxin receptors on the surface of parasympathetic neurons in the frog heart. Brain Res 680:99-107
Ullian, E M; Sargent, P B (1995) Pronounced cellular diversity and extrasynaptic location of nicotinic acetylcholine receptor subunit immunoreactivities in the chicken pretectum. J Neurosci 15:7012-23
Horch, H L; Sargent, P B (1995) Perisynaptic surface distribution of multiple classes of nicotinic acetylcholine receptors on neurons in the chicken ciliary ganglion. J Neurosci 15:7778-95
Sargent, P B (1994) Double-label immunofluorescence with the laser scanning confocal microscope using cyanine dyes. Neuroimage 1:288-95

Showing the most recent 10 out of 17 publications