PHYSIOLOGY OF MUSCARINIC SYNAPSES IN SYMPATHETIC GANGLIA

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Sympathetic ganglia convey signals that mediate adaptive responses to stress. The long-term goals of this project are to understand two fundamental aspects of normal sympathetic physiology. The first goal is to identify functional subsystems of sympathetic neurons that innervate selectively different classes of peripheral targets (eg. blood vessels vs. glands) and the second goal is to determine the integrative role of slow synaptic transmission in sympathetic ganglia. The underlying hypotheses are that functional subclasses of sympathetic neurons release different combinations of co-transmitters to control their respective targets and that slow synaptic potentials in ganglia serve to modulate the firing of repetitive action potentials thereby providing a mechanism for regulating the release of individual co-transmitters from a given class of ganglion cells. The most important aspect of this project is to provide a model for understanding the physiological significance of muscarinic and peptidergic synapses in autonomic ganglia. In addition, this research will develop an in vitro system for identifying cellular and molecular mechanisms that regulate phenotypic properties of functionally distinct sympathetic neurons. Using bullfrogs, a combination of electrophysiological and anatomical methods will be used to address four specific aims: 1) Test the hypothesis that sympathetic C cells are vasomotor neurons that utilize epinephrine (EPI), neuropeptide Y (NPY) and adenosine triphosphate (ATP) as co-transmitters. 2) Determine how muscarinic and peptidergic synaptic potentials in ganglia and the repetitive firing that they engender, each regulate the release of EPI, NPY and ATP from C neurons onto arteries. 3) Develop a tissue culture system in which a vasomotor C cells can be identified and the use patch clamp methods to characterize the membrane currents that produce and modulate the repetitive firing of action potentials. 4) Test the hypothesis that fast B and/or slow B but not C-type sympathetic neurons innervate cutaneous mucous glands and granular glands. Then find suitable anatomical markers that can be used to trace the peripheral projections of B-type neurons and to identify dissociated B neurons in tissue culture