Protective effects of the alpha 2-adrenoceptor antagonist, dexefaroxan, against degeneration of the basalocortical cholinergic system induced by cortical devascularization in the adult rat

Neuroscience. 2002;115(1):41-53. doi: 10.1016/s0306-4522(02)00406-2.

Abstract

It has been hypothesized [Colpaert, F.C., 1994. In: Briley, M., Marien, M. (Eds.), Noradrenergic Mechanisms in Parkinson's Disease. CRC Press, Boca Raton, FL, pp. 225-254] that a deficiency in the noradrenergic system originating from the locus coeruleus is a decisive factor in the progression of central neurodegenerative disorders including Alzheimer's disease, and that treatments which boost noradrenergic transmission (e.g. via blockade of alpha(2)-adrenoceptors) could provide both symptomatic and trophic benefits against the disease. Studies in the rat in vivo demonstrating that the selective alpha(2)-adrenoceptor antagonist dexefaroxan increases acetylcholine release in the cortex, improves measures of cognitive performance and protects against excitotoxin lesions, support this concept. As a further test of the hypothesis, we investigated the effect of dexefaroxan in a rat model of unilateral cortical devascularization that induces a loss of the cortical cholinergic terminal network and a retrograde degeneration of the cholinergic projections that originate in the nucleus basalis magnocellularis. Lesioned and sham-operated rats received a 28-day subcutaneous infusion of dexefaroxan (0.63 mg/rat/day) or vehicle, delivered by osmotic minipumps implanted on the day of the cortical devascularization procedure. In lesioned rats, the dexefaroxan treatment was associated with a significantly higher number and size of vesicular acetylcholine transporter-immunoreactive boutons in comparison to the vehicle treatment; this effect was most marked within cortical layer V. Dexefaroxan also significantly reduced the atrophy of cholinergic neurons within the nucleus basalis magnocellularis. Dexefaroxan had no observable effect on any of these parameters in sham-operated cohorts. These results show that systemically administered dexefaroxan mitigates cholinergic neuronal degeneration in vivo, and provide further evidence for a therapeutic potential of the drug in neurodegenerative diseases such as Alzheimer's disease, where central cholinergic function is progressively compromised.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-2 Receptor Antagonists*
  • Adrenergic alpha-Antagonists / pharmacology
  • Adrenergic alpha-Antagonists / therapeutic use
  • Animals
  • Basal Nucleus of Meynert / chemistry
  • Basal Nucleus of Meynert / drug effects*
  • Basal Nucleus of Meynert / pathology
  • Benzopyrans / pharmacology
  • Benzopyrans / therapeutic use*
  • Cholinergic Fibers / chemistry
  • Cholinergic Fibers / drug effects*
  • Cholinergic Fibers / pathology
  • Imidazoles / pharmacology
  • Imidazoles / therapeutic use*
  • Male
  • Nerve Degeneration / drug therapy*
  • Nerve Degeneration / pathology
  • Neuroprotective Agents / pharmacology
  • Neuroprotective Agents / therapeutic use
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Adrenergic, alpha-2 / physiology
  • Somatosensory Cortex / blood supply
  • Somatosensory Cortex / drug effects*
  • Somatosensory Cortex / physiology

Substances

  • Adrenergic alpha-2 Receptor Antagonists
  • Adrenergic alpha-Antagonists
  • Benzopyrans
  • Imidazoles
  • Neuroprotective Agents
  • Receptors, Adrenergic, alpha-2
  • dexefaroxan