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Drug driven conditioning in
pigeons Apomorphine is a potent direct non-addictive agonist of the neurotransmitter dopamine. Injected intramuscularly at low doses it elicits oral stereotypies in a variety of animals, from snails to humans. Clinically it is also used as an emetic and an anti-parkinson drug. In birds an injection triggers an extended bout of up to several thousand pecks. It can be shown in pigeons that this unconditioned response to apomorphine associates to contingent environamental cues so that these yield a conditioned pecking response upon a mere saline injection. Pigeons also evince a marked preference to revisit a cage in which they have received apomorphine rather than saline. Furthermore, much as the addictive psychostimulant drugs amphetamine and cocaine are known to do in mice and rats, apomorphine yields a marked response increase (sensitization) upon repeated administration. It will be argued that in pigeons this sensitization increment is due to a pavlovian conditioning process and it will be shown that it is under a precise control by environamental stimuli. The potentials of this drug conditioning model will be discussed, particularly with regard to the dopamino-glutamatergic interaction thought to underlie sensory-motor learning. Keywords: apomorphine, conditioning, pigeon, discrimination, sensitization |
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