Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 297, Issue 3, pp 227–231 | Cite as

Clonidine-induced locomotor hyperactivity in rats

The role of central postsynaptic α-adrenoceptors
  • I. Żebrowska-Łupina
  • E. Przegaliński
  • M. Słoniec
  • Z. Kleinrok


The α-adrenergic agonist, clonidine, causes sedation in normal rats. The present study demonstrates that clonidine evokes strong locomotor stimulation in rats pretreated with 6-hydroxydopamine plus reserpine. Similar, but less intensive hyperactivity is observed in rats given clonidine after combined pretreatment with 6-hydroxydopamine plus p-chlorophenylalanine plus α-methyl-p-tyrosine, or with reserpine plus low doses of yohimbine. The α-adrenolytic drugs, phenoxybenzamine, phentolamine and aceperone, as well as high doses of yohimbine, antagonise the clonidine-induced locomotor stimulation; in contrast, the dopamine receptor blocking agents, pimozide and spiroperidol, exert no antagonistic effect. The results indicate that in the brain of normal animals, clonidine predominantly activates presynaptic α-adrenoceptors on noradrenergic neurones and thereby induces sedation. After destruction of the noradrenergic fibres by 6-hydroxydopamine plus reserpine, activation of postsynaptic α-adrenoceptors prevails so that hyperactivity results.

Key words

Clonidine 6-Hydroxydopamine Reserpine Locomotor activity α-Adrenoceptors Brain Rats 


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Copyright information

© Springer-Verlag 1977

Authors and Affiliations

  • I. Żebrowska-Łupina
    • 1
  • E. Przegaliński
    • 1
  • M. Słoniec
    • 1
  • Z. Kleinrok
    • 1
  1. 1.Department of Pharmacology, Institute of Clinical PathologySchool of MedicineLublinPoland

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