Blockage of substance P-induced scratching behavior in rats by the intrathecal administration of inhibitory amino acid agonists.
Intrathecal administration of 20 micrograms of substance P induced scratching behavior in most tested rats (80%). Scratching appeared in bouts of short latency and variable duration, intensity and frequency (range 1-60, mean number of scratching bouts in one hour test: 8.93 +/- 1.86). Intrathecal administration of glycine (400 micrograms but not 66 micrograms) significantly decreased the effect of substance P on this behavior. Taurine, in dosages equimolar to glycine, abolished the response to substance P at the high dose level (700 micrograms), but did not significantly affect it at the lower level (120 micrograms). The GABAA agonist, muscimol, abolished the effect of substance P at the 3 micrograms dose level, but the 0.5 microgram dose did not produce a significant effect. Baclofen, a GABAB agonist, was highly effective in significantly reducing the action of SP at 0.9 and 0.15 microgram; only two of 8 rats receiving the low dose of baclofen (0.15 microgram) exhibited scratching. The results suggest that the spinal inhibitory amino acids modulate nociceptive impulses generated by the action of substance P in dorsal horn neurons of the spinothalamic tract.
Beyer
C
C
Institute of Animal Behavior, Rutgers, State University, Newark, NJ 07102.
Banas
C
C
Gonzalez-Flores
O
O
Komisaruk
B R
BR
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005998:Glycine / Q000008:administration & dosage; D007278:Injections, Spinal; D009118:Muscimol / Q000008:administration & dosage*; D010146:Pain / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology* / Q000502:physiology; D013654:Taurine / Q000008:administration & dosage
D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D013654:Taurine; D009118:Muscimol; D013373:Substance P; D005998:Glycine