The effect of trans-ACPD, a metabotropic excitatory amino acid receptor agonist, on the responses of primate spinothalamic tract neurons.
The responses of primate spinothalamic tract (STT) neurons to innocuous and noxious mechanical stimuli applied to the skin can be enhanced for more than an hour following prolonged noxious stimulation. This increased responsiveness is thought to reflect sensitization of dorsal horn neurons and may help account for secondary hyperalgesia and mechanical allodynia. The proposal that central sensitization is due to the activation of second messenger system was tested in this study by examining the effect of trans-ACPD (trans-D,L-1-amino-1,3-cyclopentanedicarboxylic acid), an agonist of metabotropic excitatory amino acid (EAA) receptors, introduced into the dorsal horn by microdialysis. A low dose of trans-ACPD resulted in an increase in the responses of STT cells to an innocuous mechanical stimulus (BRUSH), but no increase in the responses to noxious mechanical and thermal stimuli or in the excitation produced by iontophoretically applied EAAs. A high dose of trans-ACPD caused a transient increase in background activity, but no change in the responsiveness of spinothalamic cells to any of the test stimuli. It is concluded that low doses of trans-ACPD can selectively enhance transmission through interneuronal pathways mediating tactile inputs to spinothalamic cells.
Department of Anatomy and Neurosciences and Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555 USA.
J
J
Paleček
V
V
Palečková
P M
PM
Dougherty
W D
WD
Willis
D000200:Action Potentials / Q000187:drug effects; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D003515:Cycloleucine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D006358:Hot Temperature; D008252:Macaca fascicularis; D017551:Microdialysis; D009434:Neural Pathways / Q000166:cytology / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000008:administration & dosage / Q000494:pharmacology*; D010812:Physical Stimulation; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects*; D013116:Spinal Cord / Q000166:cytology* / Q000187:drug effects; D013788:Thalamus / Q000166:cytology* / Q000187:drug effects
D000596:Amino Acids; D009498:Neurotoxins; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane