Amphetamine exerts anomalous effects on dopaminergic neurons in neonatal rats in vivo

Francine Trent, Nakamura Shoji, James M. Tepper

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The effects of amphetamine, apomorphine and haloperidol on the spontaneous activity of electrophysiologically identified nigral dopaminergic neurons were examined with extracellular recordings in vivo in neonatal rats ranging in age from postnatal day 1 to postnatal day 28, and in adult rats. In postnatal day 1-6 pups amphetamine (5 mg/kg i.p.) produced a paradoxical increase in neuronal firing in 45% and had no effect on 30% of the 20 neurons examined. During the second week half of the neurons recorded were unresponsive to amphetamine. Typical amphetamine-induced inhibition was observed in only 25% of the neurons from postnatal day 1-6 and 50% of those from postnatal day 7-15 rats compared to 81.8% in postnatal day 16-28 pups and 100% in adults. Apomorphine (50-200 μg/kg i.p.; 5-20 μg/kg i.v.), significantly inhibited the spontaneous activity of dopaminergic neurons, including cells that previously failed to be inhibited by amphetamine, independent of age. The apomorphine-induced inhibition was consistently reversed by administration of haloperidol (0.5-2.0 mg/kg, i.p.; 50-200 μg/kg i.v.). The anomalous responses to amphetamine in early neonatal rats may be related to its paradoxical behavioral effects in human children afflicted with attention deficit disorder.

Original languageEnglish (US)
Pages (from-to)265-272
Number of pages8
JournalEuropean Journal of Pharmacology
Issue number3
StatePublished - Nov 12 1991

All Science Journal Classification (ASJC) codes

  • Pharmacology


  • (Stimulants)
  • Amphetamine
  • Attention deficit disorder
  • Dopaminergic neurons
  • Neonate
  • Substantia nigra

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