Regulation by cell interactions of amino acid neurotransmitter receptors on embryonic chick sympathetic preganglionic neurons in vitro.

Matching between the amount of neurotransmitter released by a presynaptic neuron and the number and location of neurotransmitter receptors on target neurons is fundamental to the proper functioning of the nervous system. In this thesis I have focused on one side of this matching. I have studied the regulation of receptors on sympathetic preganglionic neurons (SPN) from embryonic chick spinal cord. The cells were labeled with a fluorescent dye in vivo and placed in culture either alone or in co-culture with spinal interneurons and non-neuronal cells. I used whole cell patch clamp recordings to measure the amplitude of the responses of these cells to GABA, glycine and glutamate and compared the levels of responsiveness under varying culture conditions. The major findings of this work were that: (1) there is considerable variability in the amplitude of the responses of a single population of CNS cells to neurotransmitters; (2) the development of responsiveness of SPN to GABA, glycine and glutamate were different over time in culture; (3) there was no correlation between the amplitude of the responses of individual neurons to multiple neurotransmitters; (4) the amplitude of the responses of SPN to GABA, glycine and glutamate are regulated extrinsically by interactions with interneurons and non-neuronal cells rather than intrinsically; (5) the presence of interneurons and non-neuronal cells affects the amplitude of the responses of SPN to the three neurotransmitters differently; (6) the presence of target cells does not affect the amplitude of the responses of SPN to any of the neurotransmitters; (7) the regulation of the responsiveness of SPN to neurotransmitters most likely requires contact between cells; and (8) that spike activity may regulate the amplitude of the responses of SPN to GABA and glycine. It seems unlikely from these data that a single mechanism will be found which regulates all receptors at synapses in the CNS. Rather, it appears that each class of receptors may be regulated in a different manner.PhDBiological SciencesNeurosciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128500/2/9023532.pd