Cortical alpha 1-adrenergic regulation of acute and sensitized morphine locomotor effects

Neuroreport. 2001 Nov 16;12(16):3483-6. doi: 10.1097/00001756-200111160-00022.


The role of alpha1-adrenergic transmission was tested on locomotor effects of acute or repeated morphine (5 mg/kg, i.p.) administration. Prazosin, an alpha1-adrenergic antagonist, administered 30 min before morphine, either systemically (0.5 mg/kg, i.p.) or locally and bilaterally into the prefrontal cortex (200 pmol/side) reduced the stimulatory influence of morphine on locomotion. The progressive increase of the locomotor response induced by repeated morphine injections was blocked by a prazosin pretreatment but not the behavioral sensitization on the test day. These data suggest that blockade of cortical alpha1-adrenergic receptors reduces the expression of acute and sensitized locomotor responses to morphine, but does not prevent the induction of behavioral sensitization.

MeSH terms

  • Adrenergic alpha-1 Receptor Antagonists
  • Adrenergic alpha-Antagonists / pharmacology
  • Analgesics, Opioid / administration & dosage*
  • Animals
  • Cerebral Cortex / drug effects*
  • Cerebral Cortex / physiology
  • Drug Administration Schedule
  • Injections, Intraperitoneal
  • Injections, Intraventricular
  • Male
  • Morphine / administration & dosage*
  • Motor Activity / drug effects*
  • Motor Activity / physiology
  • Prazosin / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Adrenergic, alpha-1 / physiology*


  • Adrenergic alpha-1 Receptor Antagonists
  • Adrenergic alpha-Antagonists
  • Analgesics, Opioid
  • Receptors, Adrenergic, alpha-1
  • Morphine
  • Prazosin