Analgesic effect of agmatine and its enhancement on morphine analgesia in mice and rats.
OBJECTIVE
To study the effect of agmatine on pain and morphine analgesia.


METHODS
The effect of agmatine on pain was observed in mouse heat radiant tail-flick test, mouse acetic acid writhing test, and rat 4% saline test. Its enhancing effect on analgesia of morphine and clonidine was assessed in rat and mouse heat radiant tail-flick tests.


RESULTS
Agmatine did not significantly prolong tail-flick latency of mice, but reduced the number of acetic acid-induced writhing of mice and inhibited writhing responses to saline completely. It potentiated the analgesic effects of morphine and clonidine in dose-dependent manner and decreased the analgesic ED50 of morphine and clonidine by more than 75% in mouse heat radiant tail-flick test. These effects of agmatine were antagonized by idazoxan.


CONCLUSIONS
Agmatine has weak analgesic effects and potentiates morphine and clonidine analgesia by activation of imidazoline receptors.
Li
J
J
Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing, China.
Li
X
X
Pei
G
G
Qin
B Y
BY
D000376:Agmatine / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D007093:Imidazoles; D054755:Imidazoline Receptors; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011955:Receptors, Drug / Q000187:drug effects
D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D007093:Imidazoles; D054755:Imidazoline Receptors; D011955:Receptors, Drug; D000376:Agmatine; D009020:Morphine; D003000:Clonidine