A behavioural and pharmacological evaluation of the discriminative stimulus induced by pentylenetetrazole in the pig.

The anxiogenic nature of the interoceptive discriminative stimulus induced by pentylenetetrazole (PTZ) was investigated by examining the discriminatory behaviour of PTZ conditioned pigs during a conditioned emotional response (CER). A CER was induced in a nonoperant situation, by pairing a tone stimulus with the application of a mild, non-injurious electric shock. Subsequent presentation of the conditioned tone stimulus alone produced a generalisation to the PTZ cue. This generalisation of the conditioned emotional state (CES) to the PTZ cue was antagonised by pretreatment with diazepam (0.5 mg/kg, PO; 30 min). The PTZ stimulus was also antagonised by diazepam (0.5 mg/kg, PO; 30 min) but not by an anticonvulsant dose of ethosuximide (30 mg/kg, PO; 1-3 h), providing further confirmation of the anxiogenic nature of the PTZ cue. Our results demonstrate the validity of the PTZ discrimination paradigm in pigs as a test of anxiety.