6-Hydroxydopamine treatment of neonatal rats. II. Effects on the development of the hindlimb flexor reflex

Kirt E. Simmons, David J. Jones

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Abstract

The flexor reflex (FR) of the hindlimb was measured in rats at various ages between postnatal days (PND) 12-45, in vehicle-treated control rats and in rats treated with 6-hydroxydopamine (6-OHDA) (100 mg/kg, i.p.) on the first and second days after birth. The hindlimb FR was elicited by graded electrical stimulation of the footpad (0.1-2.0 mA) and quantified by the amplitude of the flexion in grams. The half maximal FR response was evoked by 1.2 mA and was 2-3 g in animals at PND 12-17 and 9-10 g in animals on PND 30 and 45. A similar age dependency was evident in the maximum hindlimb FR evoked by 2.0 mA; the maximum FR was 4.7 ± 0.5 g on PND 12 and 24 ± 2 g on PND 45. In rats treated with 6-OHDA, the strength of the FR was similar to that of the controls up to PND 15. However, the FR was increased 25% by PND 17 and 200% by PND 45 in the 6-OHDA-treated animals, versus controls. Pretreatment with clonidine (100 μg/kg, i.p.), which activates α1 receptors under the current experimental conditions, did not enhance the FR in control animals. However clonidine pretreatment caused an increase of 400-800% in the FR in the 6-OHDA-treated animals at PND 15 and beyond. Our companion paper demonstrated that as early as PND 5, there was a significant increase (P < 0.05) in alpha1 receptors in the spinal cord of 6-OHDA-treated animals, versus the controls34. The temporal disparity between increased alpha1 receptors and the increased FR in 6-OHDA-treated animals suggests that factors other than increased α1 receptors might be involved in the enhancement of the FR.

Original languageEnglish (US)
Pages (from-to)231-236
Number of pages6
JournalBrain Research
Volume611
Issue number2
DOIs
StatePublished - May 21 1993

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Keywords

  • 6-Hydroxydopamine
  • Hindlimb flexor reflex
  • Motor reflex
  • Spinal cord
  • α Receptor

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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