title: Ultra low concentrations of morphine increase neurite outgrowth in cultured rat spinal cord and cerebral cortical neurons.
abstract: The present study was undertaken to evaluate the effects of ultra low concentrations (10(-9) or 10(-14)M) of morphine on neurite elongation in cultured neurons dissociated from rat spinal cords and cerebral cortex. In fetal serum (FS) or fetal serum-free supplemented with cAMP media, the length of longest neurite was significantly increased by 10(-9) or 10(-14)M morphine. For example, 10(-14)M morphine increased neurite length by 24 +/- 0.5% and 27 +/- 0.3% in spinal cord neurons, and 18 +/- 0.2% and 17 +/- 0.6% in cortical neurons. Morphine (10(-6)M) had no significant effect on neurite length of spinal and cortical neurons. The relative frequency distribution of neurite length revealed 61 +/- 2.7% of spinal neurons and 48 +/- 2.6% of cortical neurons are responsive to ultra low concentrations of morphine. In the responsive populations, morphine (10(-14)M) enhanced the neurite outgrowth in spinal neurons by 58 +/- 0.9% and 48 +/- 1.2% and in cortical neurons by 31 +/- 0.6% and 28 +/- 0.9% in FS and cAMP-supplemented media, respectively. Pretreatment with naloxone did not prevent the morphine effect. The result shows that morphine at ultra low concentrations enhances neurite outgrowth of spinal and cortical neurons via a naloxone-independent mechanism.
authors.affiliation: Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, PO Box 70577, Johnson City, TN 37614, USA.
authors.forename: Eugen
authors.initials: E
authors.lastname: Brailoiu
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hoard
authors.forename: G Cristina
authors.initials: GC
authors.lastname: Brailoiu
authors.forename: Michelle
authors.initials: M
authors.lastname: Chi
authors.forename: Ramona
authors.initials: R
authors.lastname: Godbolde
authors.forename: Nae J
authors.initials: NJ
authors.lastname: Dun
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology
chemical_list: D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D009020:Morphine