Behavioral and neurochemical changes after intracisternal capsaicin treatment of the guinea pig.
Guinea pigs were treated with 125-150 micrograms capsaicin intracisternally (i.c.) or intraperitoneally (i.p.). Tested up to one week later, i.c.-treated animals showed reduced behavioral responses to the irritating effects of capsaicin applied to the eye or nose, to ether vapor, cigarette smoke and to hot water (50 degrees C) applied to the forepaw or ear. The concentrations of substance P (SP)- and neurokinin-immunoreactivity were decreased in the medulla oblongata but not in the trigeminal root of i.c.-treated animals as compared to controls or i.p.-treated guinea pigs. These results suggest that i.c. capsaicin causes a degeneration of the central terminals of chemo- and thermonociceptive afferent neurons, some of which contain the putative neurotransmitters SP and neurokinin A.
Gamse
R
R
Saria
A
A
Lundberg
J M
JM
Theodorsson-Norheim
E
E
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002211:Capsaicin / Q000008:administration & dosage / Q000633:toxicity*; D005260:Female; D006168:Guinea Pigs; D007276:Injections, Intraventricular; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism; D009297:Nasal Mucosa / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D015288:Neurokinin A; D013373:Substance P / Q000378:metabolism; D013997:Time Factors; D014279:Trigeminal Nucleus, Spinal / Q000187:drug effects / Q000378:metabolism
D009419:Nerve Tissue Proteins; D013373:Substance P; D015288:Neurokinin A; D002211:Capsaicin