Research Report Myelination changes in the rat optic nerve after prenatal exposure to methamphetamine Pedro Melo a,b , Vicente Zanón Moreno c , Sheila Pons Vázquez c , Maria Dolores Pinazo-Durán c , Maria Amélia Tavares a,b, ⁎ a Institute of Anatomy Professor J. A. Pires da Silva, Faculty of Medicine of the University of Porto, Alameda Hernâni Monteiro, 4200-319 Porto, Portugal b Institute for Molecular and Cell Biology, Porto, Portugal c Ophthalmology Research Unit “Santiago Grisolia”, University Hospital Doctor Peset, Valencia, Spain ARTICLE INFO ABSTRACT Article history: Accepted 8 May 2006 Available online 12 July 2006 The use of psychostimulants during adolescence and early adult life has increased in recent years. It is known that these substances affect the sensory systems, and the optic nerve has been shown to be a target tissue. This work was conducted to evaluate the effects of prenatal exposure to methamphetamine (MA) on the developmental pattern of the rat optic nerve. Pregnant female rats were given 5 mg/kg body weight/day MA, s.c., in 0.9% saline from gestational days 8 to 22. The control group was injected with an isovolumetric dose of 0.9% saline. Animal model parameters, such as gestational body weight evolution, food intake and pups parameters were registered. The offspring were sacrificed at postnatal days (PND) 7, 14 and 21. Morphometric analyses were performed at light and electron microscopic levels on optic nerve cross sections; parameters measured included optic nerve diameter and area, axonal density, total number of axons and myelin thickness. Myelin basic protein (MBP) was measured by western blotting in optic nerve samples at PND14 and PND21. The animal model parameters, such as maternal and pup weight, showed no significant differences between MA and control groups. Optic nerve diameter was smaller at PND7 in the male MA group and in both male and female MA groups at PND21. The mean cross-sectional area was smaller at PND14 in the male MA group and in both male and female groups at PND21. The total number of myelinated axons did not vary between groups at any of the studied ages. The myelin thickness of the axons in MA-treated females was thinner when compared with the respective control group at PND21. No other differences were found concerning myelin thickness. There was a reduction of MBP protein expression in MA-injected females at PND14 and PND21. The combined results suggest that prenatal exposure to MA affects the myelination process. © 2006 Elsevier B.V. All rights reserved. Keywords: Rat Optic nerve Methamphetamine Myelin Myelin basic protein BRAIN RESEARCH 1106 (2006) 21 – 29 ⁎ Corresponding author. Institute of Anatomy Professor J. A. Pires da Silva, Faculty of Medicine of the University of Porto Alameda Hernâni Monteiro 4200-319 Porto, Portugal. Fax: +351 22 55113617. E-mail address: anatclin@med.up.pt (M.A. Tavares). 0006-8993/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2006.05.020 available at www.sciencedirect.com www.elsevier.com/locate/brainres