Unconditioned Nictitating Membrane Research Articles

Central cholinergic blockade by scopolamine and habituation, classical conditioning, and latent inhibition of the rabbit’s nictitating membrane response

Rabbits injected with scopolamine hydrobromide (1.5 mg/kg) were contrasted with control animals injected with scopolamine methylbromide or saline in terms of habituation of the unconditioned nictitating membrane response (NMR), classical defensive conditioning, and latent inhibition using auditory and visual conditioned stimuli. Scopolamine hydrobromide disrupted classical conditioning in comparison with drug controls, but had no adverse effects on habituation of the unconditioned reflex or on latent inhibition. The drug also raised thresholds of the auditory (but not visual) CS for eliciting the conditioned NMR. Results were discussed in terms of presumed cholinergiclimbic system involvement in Pavlovian conditioning and inhibition.