Abstract: NE, Gly, GABA and L-Glu were topically applied to the dorsal surface of lumbar spinal cord or iontophoretically injected into the spinal dorsal horn to observe their effects on segmental (SP) ant descending (DP) spinal field potentials on anesthetized (or conscious) and immobilized rats. In the group of topical application(TA), both waves N and P of SP and DP were seen to be reduced markedly in their amplitudes following TA of NE. A significant decrease in wave N’s magnitude and a remarkable increase in wave P’s size in both SP and DP were shown during TA of Gly, GABA and L-Glu. In the group of iontophoretical injection(II), either reduced or enhanced effect was shown during II of NE.activity of spinal interneurons and/or intraspinal terminanls of primary afferents.

Key words: neurotransmitters, spinal field potential, spinal interneurons, pre-and/or postsynaptic inhibition