GABAergic mechanisms in morphine analgesia.

There are coflicting reports regarding the role of GABA in morphine analgesia. While-sorne investigators have reported that treatment with GABAA receptor agonist muscimol and GABA transaminase inhibitors potentiates morphine analgesia (2.4.6) others have reported antagonism of morphine analgesia (8.10). In view of these conflicting reports and since the analgesic profile 'of THIP, a GABAA receptor agonist. has-some similarity with that of morphine (1). in the present study we have investigated on morphine analgesia. the effect of pretreatment with muscimol, a GABAA receptor agonist, diazepam, a drug which enhances binding of GABA to GABAA receptors and bicuculline, a GABAA receptor antagonist (3). We have also investigated on morphine analgesia, the effect of pretreatment with sodium valproate, which increases brain GABA levels by inhibiting its degradation and reputake (5). and isoniazid, which decreases GABA levels by inhibiting its synthesis (9).