Stereotyped behavior affected by peripheral and intracerebroventricular apomorphine administration in pigeons

In pigeons, peripheral injection of apomorphine HCl (1.5 mg) produced a rapid pecking response while intracerebroventricular administration of the drug (60 μg) was ineffective in this respect. Both peripheral and to a larger extent central treatment with apomorphine stimulated another activity, that is headshaking. The frequency of other behavioral patterns was either decreased (preening) or unaffected (yawning, stretching) following both treatments. Together with previous studies, these data suggest that (a) apomorphine stimulates pecking in pigeons by activating dopaminergic mechanisms lying in brain areas situated away from the ventricles; (b) dopaminergic mechanisms situated in periventricular regions may take part in the control of some patterns, e.g. headshaking, and (c) other activities do not appear to depend directly on these mechanisms.