Excitatory amino acid receptors and nociceptive neurotransmission in rat spinal cord.
Excitatory amino acid (EAA) receptor agonists were tested for their effect on identified rat spinal neurons. Only 75% of the spinal neurons tested increased their firing rate in response to iontophoretic application of one or more of the EAA receptor agonists, N-methyl-D-aspartate (NMDA), quisqualate (Quis), (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid HBr (AMPA), and kainate (KA). NMDA and Quis or AMPA activated primarily nociceptive neurons (60% of these neurons were projection neurons) in the rat spinal cord. KA-activated neurons were primarily classified as low threshold neurons. Both NMDA and AMPA, at subthreshold doses, significantly increased neuronal responses to peripheral noxious mechanical stimulation; NMDA also significantly increased neuronal responses to peripheral noxious thermal stimulation. Iontophoretically applied phencyclidine (PCP) decreased NMDA-induced firing in 100% of the cells tested while Quis-induced firing was blocked by PCP in only 33% of the cells tested. The reported analgesic effects of PCP in humans may result from a spinal action involving its well documented interaction with NMDA receptors.
Aanonsen
Linda M
LM
Department of Cell Biology and Neuroanatomy, University of Minnesota, Minneapolis, MN 55455, U.S.A. Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, U.S.A.
Lei
Sizheng
S
Wilcox
George L
GL
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D007478:Iontophoresis; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010622:Phencyclidine / Q000494:pharmacology; D010812:Physical Stimulation; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D000596:Amino Acids; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D015763:2-Amino-5-phosphonovalerate; D010622:Phencyclidine