Amphetamine stereotypy in cats and neurotransmitter interactions in the caudate nucleus. II. Effects of intracaudate injection of leu-enkephalin and naloxone.

In cats, injection of leu-enkephalin (LEU-ENK) and naloxone (NAL) into the rostrodorsal part of the caudate nucleus 30 minutes after amphetamine i. p. induced quantitative and qualitative changes in amphetamine stereotypy. LEU-ENK decreased the amplitude or the number of the focused stereotyped movements and increased the ipsilateral at the expense of the contralateral head turnings. NAL increased the duration of the phase with head movements, the number of circlings and the number of other locomotor behaviors, as well as the number of the contralateral head turnings at the expense of the ipsilateral ones. LEU-ENK and NAL injected alone (without pre-amphetamine) had not any effects on the animal behavior. The results suggest a role for enkephalins and possibly for other naloxone-sensitive opiates in the behavioural responses to amphetamine in cats.