Premium
Anti‐nociception Induced by Systemic or PAG‐microinjected Lysine‐acetylsalicylate in Rats. Effects on Tail‐flick Related Activity of Medullary Off‐ and On‐cells
Author(s) -
Tortorici Victor,
Vanegas Horacio
Publication year - 1995
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1995.tb00706.x
Subject(s) - nociception , rostral ventromedial medulla , microinjection , pharmacology , chemistry , reflex , medulla , systemic administration , medulla oblongata , hyperalgesia , neuroscience , anesthesia , central nervous system , medicine , receptor , psychology , in vivo , biochemistry , biology , microbiology and biotechnology
Previous experiments using metamizol have shown that this non‐steroidal anti‐inflammatory drug (NSAID) produces a central anti‐nociceptive effect probably through neural substrates that also support the analgesic effects of opiates, such as the periaqueductal grey matter (PAG) and the off‐ and on‐cells of the rostral ventromedial medulla (RVM). Off‐ and on‐cells have been postulated to respectively inhibit and facilitate nociceptive transmission, since the heat‐elicited tail flick reflex (TF) occurs only after off‐cells have decreased (pause), and on‐cells have increased (burst) their activity. The aim of the present study was to examine whether the effect of metamizol upon TF and off‐ and on‐cells responses could be generalized to other NSAIDs such as, in this case, lysine‐acetylsalicylate (LASA). Fifty‐nine off‐ and on‐cells of the RVM were recorded in lightly anaesthetized rats. Systemic administration (200 and 300 mg/kg) or PAG microinjection (30, 50 and 100 μg) of LASA caused retardation of the heat‐elicited off‐cell pause, on‐cell burst and the corresponding TF. Neuronal responses and TF retained their mutual time relationship but shifted simultaneously toward longer latencies. This anti‐nociceptive effect of LASA was dose‐dependent, present 5 min after administration and reached a maximum in 30 min for both administration methods. These data confirm that analgesics typically defined as peripherally‐acting, such as metamizol and LASA in this study, may also have an anti‐nociceptive effect by acting directly upon PAG, and suggest that this central effect involves the RVM off‐ and on‐cells.