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Weithers S, Larson AA. 
“Desensitization To Intratbecal Substance P-induced Biting And Scratching: Effect Of LSD And Chronic Pain”. 
J. Neurochem.. 1985;44(Suppl).
Intrathecal (i.t.) administration of Substance P (SP) has been previously reported to elicit biting and scratching (B&S) in mice. Both SP and serotonin are reported to be elevated in chronic pain. Desensitization to SP has been found to occur to some effects of SP, leading us to question whether this also occurs to the SP-induced B&S response. While LSD has been thought to by altering serotonergic activity, LSD has also been found to enhance SP activity both in vivo and in vitro. It was therefore also of interest to determine LSD's effect on SP-induced B&S in naive mice as well as those in chronic pain. A single i.t. injection of 10 ng of SP produced B&S behavior similar in magnitude to that previously reported. Repeated injections of this dose of SP at 1 min intervals for 3 min resulted in tachyphylaxia to the ability of SP to elicit B&S. A single injection of 25 mcg/kg of LSD i.p. 15 min prior to challenge with SP i.t. (3X) protected against the development of tachyphylacis to SP but had no effect on a single injection to SP. Mice with a Freund's Adjuvant (FA)-induced chronic inflammatory condition did not differ in their behavioral response to a single injection of 10 ng of SP i.t., however the degree of tachyphylaxis was significantly less after repeated injections of SP than in control mice. A single injection of LSD to FA-pretreated mice resulted in tachyphylaris to SP that was greater in magnitude than that seen in any other treatment group.
Notes # : 10th Meeting Int. Soc. for Neurochem., Riva Del Garda, Italy
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