| Research Abstract |
It is widely accepted that neuropeptides whose effects on neurones usually last long time may play important role in the nervous system as neurotransmitters of neuromodulators. Many kinds of neuropeptides were already discovered. However, almost all of those peptides were found as biologically active substances on intestinal, glandular or vasular smooth muscles. If we want to find "active peptide specifically on the nervous system", we should use nerve tissue for the screening tool. In the present study, therefore, we use in vitro preparation of the newborn rat spinal cord. At the age of 0-8 days, the whole spinal cord was taken and hemisected, and sucking electrodes were applied to the lumbar dorsal and ventral roots. The stimulation electrode was also put on the lateral funiculus of the cervical segments. When the interested substance was bath applied to this preparation, the effect on the following parameters were physiologically evaluated;1)the ventral root potentials 2)the dorsal
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root potentials 3)monosynaptic reflex on the ventral roots following the dorsla root stimulation 4)fast response of the lumbar ventral roots following the stimulation of the cervical lateral funiculus. Using this preparation, we first tried to apply known tra-smitter candidates; GABA, glutamate, nordrenaline, serotonin, substance P, TRH, neurotensin, CGRP and so forth, and found that the effects of substances were different each other. It is, therefore, possible to use the preparation as a tool to find the "unknown" peptides. Acetone-HCl extracts from 50kg porcine spinal cord were separated on the reverse phase preparative HPLC. Aliguot of each collecting tube was applied to the bath, and the effects on the above 4 parameters determined. There are several peaks which show strong actions on the spinal cord preparation, whereas those on the peripheral tissues are minimal. Amino acid analysis of one of them revealed that the active substance may be a substance P fragment: substance P (6-11). We are now in the midst of the investigation on the other 5-6 active peaks. Less
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