Role of the mesopontine area in the circling behavior induced by apomorphine in rats bearing unilateral lesion of the entopeduncular nucleus

Mario G. Murer, Luis A. Riquelme, Javier Stern, Jorge H. Pazo

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6 Scopus citations


The role of the mesopontine area and superior colliculus in turning behavior induced by systemic administration of apomorphine was studied in rats bearing a unilateral entopeduncular lesion. Bilateral electrolytic damage of the superior colliculus resulted in an enhancement of the ipsilateral circling response to apomorphine, perhaps as a consequence of an increased locomotor drive in such animals. Bilateral electrolytic lesions of the mesopontine area decreased apomorphine-induced turning in entopeduncular rats, while a bilateral kainic acid lesion of the same region was ineffective. It was concluded that the pedunculopontine nucleus and adjacent reticular formation are not an essential link for the striopallidal complex output mediating circling in this model. Fibers running through this region could be implicated in the expression of the behavior under study. Since a unilateral electrolytic lesion of the mesopontine area contralateral to the damaged entopeduncular nucleus reduced drug-induced turning, we propose that an uncrossed pathway from the intact striopallidal complex mediates circling in our rats.

Original languageEnglish (US)
Pages (from-to)37-43
Number of pages7
JournalBehavioural Brain Research
Issue number1
Publication statusPublished - Oct 25 1991



  • Apomorphine
  • Basal ganglion
  • Entopeduncular nucleus
  • Mesopontine area
  • Superior colliculus
  • Turning behavior

ASJC Scopus subject areas

  • Behavioral Neuroscience

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