Tonic immobility: effects of dopamine receptor blockade and stimulation

Blockade of dopaminergic receptors by haloperidol enhanced the duration of tonic immobility in chickens. Apomorphine, a dopamine receptor agonist, produced short durations. Apomorphine also produced an increase in stabilimeter activity. These data suggest dopaminergic involvement in tonic immobility, and support a competing response interpretation of the apomorphine effect.