Haloperidol impairs classical nictitating membrane conditioning in rabbits when stimulation of the pontine nuclei is used as a conditioned stimulus

Rabbits classically conditioned with stimulation of the pontine nuclei as a conditioned stimulus (CS) and a corneal air puff as an unconditioned stimulus (US) were injected with haloperidol (250 μg/kg). Three different stimulation CS intensity levels were used. Haloperidol administration significantly decreased the number of conditioned responses during training at all CS intensity levels with the greatest impairment seen when medium and low levels of stimulation were delivered as a CS. These results provide evidence that haloperidol disrupts classical conditioning through actions at central brain sites (i.e., sites at or efferent to the point of stimulation) and not in pathways normally involved in projecting peripheral CSs to more central locations.