The long-term goal of this study is to determine the role of glutamate modulation in the generation of patterned output by identified PVN neurons. Experiments will be performed in acute hypothalamic slices using a combination of electrophysiological, anatomical, and in situ hybridization methods. We will use whole-cell patch-camp recordings to monitor changes in resting, voltage-gated and synaptic currents in response to mGluR activation, and pharmacological/ionic manipulations will be performed to isolate the receptor subtypes, ionic currents and second messenger mechanisms involved. Recorded cells will be marked with an intracellular dye, and they will be identified using antisera specific for different hypothalamic neuropeptides and non-radioactive riboprobes to label specific mRNA. The specific bypotheses to be test are: 1) mGluR activation enhances PVN cell excitability by reducing postsynaptic leak and voltage-gated k+ currents; 2) specific mGluR subtypes and 2nd messengers are responsible for the different mGluR actions at pre- and postsynaptic sites; 3) mGluRs play a role in the synaptic regulation of PVN neurons; 4) magnocellular and parvocellular neurons, and presynaptic neurons innervating them, express similar mGluR subtypes. The patterned electrical behaviors of hypothalamic neurons are likely to be under neuromodulatory control, but neuromodulation in the hypothalamus remains largely unexplored. These studies will provide basic information on the glutamate modulation of identified subpopulations of hypothalmic neurons. Assigning modulatory actions to glutamate to pre- and postsynaptic sites of specific hypothalamic subpopulations will enhance our understanding of the synaptic mechanisms that shape the electrical activity of neurons that control endocrine and autonomic function, and may provide the basis for future clinical pharmaceutical applications.
