DEVELOPMENT AND MODULATION OF PRESYNAPTIC ION CHANNELS

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The proposal requests salary support for the research program that I am developing. As such, it is focused on two related, but specific areas of research developed in the laboratory over the past two years: (1) development of presynaptic ion channels and their role at cholinergic varicosities in vitro, and (2) somatostatin modulation of neuronal calcium (Ca++ ) channels. Both are integral parts in my long-term goal to develop a strong research program in the development, regulation, and modulation of neuronal presynaptic function. The first specific aim is focused on the development of presynaptic ion channels and their role at cholinergic varicosities in vitro. These experiments are designed to study the induction of presynaptic specialization (Ca++ and calcium-activated K+ channels) expressed at transmitter-releasing varicosities that form along neurites in cultures of Xenopus spinal cord neurons and myocytes. Using patch clamp techniques, I propose to (1) characterize directly the types of currents present at newly formed presynaptic structures, (2) determine their role in transmitter release regulation, and (3) identify cell-cell interactions that regulate the expression of these specializations. From these studies should come a more thorough understanding of motor nerve terminal Ca++ and calcium-activated K+ channels, their role in transmitter release and the induction of presynaptic specialization. The second specific aim is focused on the mechanisms of modulation of Ca++ channels in parasympathetic neurons. The effects of somatostatin on Ca++ currents will be studied in ciliary ganglion neurons as a model for modulation that occurs at choroid nerve terminals. It is very difficult to study directly the modulation of presynaptic ionic currents in this preparation. This is due, in large part, to the small size and inaccessibility of the transmitter releasing regions. Acutely dissociated ciliary ganglion neurons will be used in vitro as a model, and using patch clamp techniques, I propose to elucidate the signal transduction cascade that couples somatostatin receptors to inhibition of Ca++ channels. The proposed experiments will provide valuable insights into the mechanisms of modulation of Ca++ channels. The Independent Scientist Award (NINDS - RCDA) would provide the freedom to pursue these research goals without large demands on my time for teaching and administrative duties. The Department of Neuroscience at the University of Pittsburgh is an ideal environment in which I can both contribute to, and draw from, an atmosphere of scientific exchange. There are many researchers in this department engaged in research addressing some aspect of synaptic physiology (LTP, NMDA receptor studies, motor control, ion channel regulation, and biochemical studies of synaptic transmission). In many ways, this is an ideal environment for me to grow professionally, and develop a strong research program in synaptic physiology.