The aim of this research program involves elucidation of the ion permeability mechamisms expressed by primary and clonal cells cultures from the embryonic mammalian CNS and from neuronal-glioma tumor, from endocrine pituitary and from immune tissue. These mechanisms are considered critical in the physiology and diverse functions of the various cellular phenoyypes. Specific lines of investigation include projects on embryonic CNS neurons cultured from spinal and suprapinal regions, clonal and primary pituitary cells, and clonal and primary effector lymphocytes. Electrophysiological measurements of excitability are made in membrane patches or in whole-cells, using either low-resistance patch-clamp techniques or high-resistance microelectrodes for recording. The different assay techniques provide complementay data for characterizing the membrane and cytoplasmic mechanisms underlying ion conductances in these cells. Principle observations this year include the following: 1) simultaneous optical and electrical assays of primary CNA neurons and clonal pituitary cells have been developed, allowing correclation of excitable membrane events and [Ca2+]i changes; 2) electrical recording of membrane capacitance under different secretory conditions correlates well with hormone secretion rates, presumably reflecting increased incorporation of organelle membrane into the cell wall; 3) cell-sorted motoneurons exhibit a full complement of ionic conductances, including one previously uncharacterized, and respond to aminoacids in well-recognizable fashions; 4) the steroid anesthetic alphaxalone amplifies GABA-mediated inhibition in a barbiturate-like way and directly activates inhibotory conductance in a GABAmimetic mannner with l00 fold greater potency than barbiturate anesthetics; 5) phosphoinositide metabolism contributes to the development of hormonally-indiced K+ conductance in clonal pituitary cells; 6) skeletal muscle secretes a factor(s) that regulates neuronal excitability in embryonic sensory neurons; and 7) killer-type lymphocytes are electrically exicitable.
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