Dyskinetic, writhing-like movements, similar to those produced in mice after an intraperitoneal (IP) injection of acetic acid, were elicted by intrathecal (IT) injection of GABA, glycine, taurine or beta-alanine. Baclofen and muscimol failed to produce this behavior. While acetic acid-induced writhing is inhibited by narcotic and nonnarcotic compounds, GABA-induced writhing was found to be insensitive to pretreatment with either morphine or capsaicin. Moreover, acetic acid-induced writhing does not appear to involve GABAergic transmission as IT injections of nipecotic acid did not alter the intensity of response to IP acetic acid while it enhanced the response to IT GABA. Writhing induced by glycine was not inhibited by strychnine at subconvulsive doses, suggesting that it involves an action at strychnine-insensitive receptors. Together these data suggest that while the dyskinetic movements produced by inhibitory amino acids do not appear to reflect an alteration in nociception, they may mimic either the motor response to abdominal pain or spasticity.
Bibliographical noteFunding Information:
The authorw ishes to thankD r. David R. Brown for his editorial assistancein the preparationo f this manuscriptT. his work was supported by USPHS Grants NIDA09040a nd NIDA09140.