Project Number: Z01 HL 00017-02 LBG
Period Covered: July 1, 1976 through September 30, 1977
Title of Project: Acetylcholine Receptors in the Developing Nervous System
Names, Laboratory and Institute Affiliations, and Titles of Principal Investigators and All Other Professional Personnel Engaged on the Project:
PI: Hiroyuki Sugiyama, Visiting Associate, LBG NHLBI
Marshall Nirenberg, Chief, LBG, LBG NHLBI
Lab/Branch: Laboratory of Biochemical Genetics
Section:  Section on Molecular Biology
Institute and Location: NHLBI, NIH, Bethesda, Maryland 20014
Total Man Years: 1.6
Professional: 1.3
Other: 0.3
Summary of Work:
The goal of this project is to define the properties of muscarinic and nicotinic acetylcholine receptors and acetylcholinesterase during development of chick embryo retina.  Thus far we have elucidated (1) the specificity and affinities of muscarinic and nicotinic acetylcholine receptors for receptor activation and antagonists, (2) the number of receptors were defined as a function of developmental age of the retina, and (3) the location of nicotinic and muscarinic receptors within the retina was determined.
Project Description:
Objectives:  The objectives are to define the biochemical properties of acetylcholine receptors before and after synaptogenesis in the retina.
Major Findings:  Neurons dissociated from chick embryo retina and maintained in vitro were found to reaggregate and form, in vitro, approximately 1 x 10^9 synapses per mg of protein.  Three types of synapses and several subtypes were identified which closely resemble those of the intact retina.
Chick embryo retina was found to be a rich source of both muscarinic and nicotinic acetylcholine receptors.  Both muscarinic and nicotinic acetylcholine receptors are synthesized before synapses appear in the retina; however, during development, nicotinic acetylcholine receptors become associated predominantly with neurites in the synaptic layers of the retina.  Muscarinic acetylcholine receptors also were found to localize in the inner synaptic layer of the retina, but the receptor distribution differs from that of nicotinic acetylcholine receptors.  The properties of muscarinic acetylcholine receptors were determined at different developmental ages and were compared with the properties of muscarinic inhibitory and excitatory receptors of neuroblastoma and hybrid cells.
Significance to Biomedical Research:  Information was obtained which serves as a basis for further studies on the role of acetylcholine receptors in synapse formation.
Proposed Course: Further studies on receptor properties are planned.