Enkephalins interact with substance P-induced aversive behaviour in mice.
The effect of the endogenous opioid peptides, methionine-enkephalin (Met-ENK), beta-endorphin (beta-END) and dynorphin-(1-17) (DYN) on the aversive behavior produced by intrathecal (i.t.) administration of substance P (SP) was studied in mice. A low dose of i.t. administered Met-ENK gave a marked reduction of the SP-induced response. In the tail-flick assay, such doses of Met-ENK were ineffective in producing antinociception. At much higher doses, however, Met-ENK obtained antinociceptive activity. In contrast, beta-END and DYN had about the same potency in inhibiting the SP-induced behavioural response and in the tail-flick test, respectively. These results suggest that opioid peptides, particularly enkephalin neurons in the spinal cord influence SP-induced aversive behaviour.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000008:administration & dosage* / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000008:administration & dosage* / Q000378:metabolism; D007278:Injections, Spinal; D051379:Mice; D009619:Nociceptors / Q000187:drug effects*; D010146:Pain / Q000503:physiopathology; D011930:Reaction Time / Q000187:drug effects; D013373:Substance P / Q000008:administration & dosage* / Q000378:metabolism; D001615:beta-Endorphin / Q000008:administration & dosage* / Q000378:metabolism
D013373:Substance P; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins