Discriminative stimulus effects of presynaptic GABA agonists in pentobarbital-trained rats

GABAA positive modulator and NMDA antagonist-like discriminative stimulus effects of isoflurane vapor in mice

“…In pigeons trained to discriminate valproic acid from vehicle, clonazepam produced full substitution, whereas diazepam only partially substituted and pentobarbital failed to substitute (Picker et al 1985). Valproic acid produces full substitution in rats trained to discriminate pentobarbital from saline (Grech and Balster 1994). In monkeys discriminating benzodiazepines from saline, valproic acid fails to substitute when given alone (Ator and Griffiths 1997), however, when administered in combination with midazolam it produce a leftward shift in the midazolam dose-effect curve (McMahon and France 2003).…”

“…The reason for this difference is unclear but it does appear to be the case that tiagabine has discriminative stimulus effects that overlap poorly with prototypic GABA A positive modulators. For instance, tiagbine only produces partial substitution in pentobarbital-trained rats (Grech and Balster 1994) and fails to substitute in diazepam-trained rats (Nielsen et al 1991). Additional studies examining drugs which produce GABA A positive modulatory effects by other mechanisms will be necessary to determine if tiagabine is unique in it’s ability to enhance GABA levels without demonstrating appreciable isoflurane-like discriminative stimulus effects.…”

AND and AND-OR drug mixture discriminations in rats: generalization to single drugs and drug mixtures

“…For example, it is known that rats trained to discriminate (+)amphetamine typically show partial generalization to nicotine (Reavill and Stolerman 1987;Druhan et al 1991), whereas rats trained on barbiturates do not generalize to nicotine (Overton 1977(Overton , 1983; the partial generalization to nicotine is probably associated with the amphetamine component of the training mixture. Conversely, the partial generalization to midazolam is probably associated with the pentobarbitone in the training mixture, since barbiturates can generalize to midazolam in rats, but amphetamine does not (Schechter 1981;Grech and Balster 1994). The failure to see generalization from the training mixture to ca¤eine is not surprising, since neither amphetamine nor barbiturates generalize with it (Oka et al 1980;Clark et al 1995).…”

Discriminative stimulus effects of tiagabine and related GABAergic drugs in rats

“…It produced 50% drug lever responding in rats trained to discriminate muscimol from vehicle (Jones and Balster 1998) and did not generalise in pentobarbital-trained rats (Grech and Balster 1994). In other drug discrimination studies in our laboratory, tiagabine showed no generalisation in gaboxadol-trained rats or in zolpidem-trained rats (McDonald et al 2007).…”