Dougherty Patrick M, Paleček Jiri, Palečková Veronica, Willis William D
Department of Anatomy and Neurosciences and The Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX 77555-0843, USA Departments of Neurosurgery and Neuroscience, Johns Hopkins Medical School, Meyer 5-109, Baltimore, MD 21287-7509, USA Institute of Physiology, Czech Academy of Sciences, 142 20 Prague, Czech Republic III Medical Faculty, Department of Physiology, Charles University, Prague, Czech Republic.
Pain. 1995 Jun;61(3):411-425. doi: 10.1016/0304-3959(94)00222-Z.
The responses of 25 spinothalamic tract (STT) neurons to mechanical and thermal stimulation of the skin, as well as to a battery of iontophoretically applied excitatory amino acids (EAAs), were tested before and then during microdialysis of substance P (SP) or neurokinin A (NKA) into the dorsal horn of anesthetized monkeys. Neither peptide had significant effects on the background activity or the responses to mechanical or thermal stimulation of the skin. However, each peptide produced significant increases in the responses to iontophoretic application of one or more EAAs. In addition, following combined application of the EAAs and either SP or NKA, the responses of the cells to mechanical stimulation of the skin increased. Combined application of SP and NKA failed to produce an increase in responses to either the EAAs or to cutaneous stimuli that was greater than that produced by either peptide alone. It is concluded that SP and NKA produce an increase in the responses of STT cells to iontophoretic applications of EAAs and the combined effects of these compounds produce sustained increases in responses to mechanical stimulation of the skin. These changes mimic those observed when STT cells are sensitized by peripheral noxious stimuli, suggesting that the mechanism of induction and expression of sensitization involves the facilitation of dorsal horn neuron responses to EAAs by tachykinins.
