title: Melatonin promotes distal dendritic ramifications in layer II/III cortical pyramidal cells of rats exposed to toluene vapors.
abstract: We have previously shown that toluene inhalation produces significant impairments in the basilar dendritic outgrowth of pyramidal cortical cells. This neurotoxic effect was markedly inhibited by melatonin administration at a dose of 5mg kg(-1). The present study was designed to determine whether toluene and melatonin equally affect all basilar dendritic segments or if a differential response exists between the segments. Twenty-eight male mice were weaned at postnatal day 21 (P21) and randomly assigned to either the control (C; n=10,) or toluene (T; n=18) group. Between P22-P32, male rats were placed into a glass chamber and exposed to either toluene vapors (5-000-6000 ppm) or clean air for 10 min a day. When toluene exposure ended (P32), animals were further assigned to the following experimental groups: (a) control/saline (C/S; n=10), (b) toluene/saline (T/S; n=10), or (c) toluene/melatonin 5mg kg(-1) (T/M; n=8). Melatonin or vehicle solutions were administered daily between P32 and P38. Forty-eight hours after the final toluene exposure, the animals were sacrificed, and the pyramidal cortical cells were stained using the Golgi-Cox-Sholl procedure. The number of basilar dendritic branches/order was counted using the centrifugal ordering method. The results indicate that (i) toluene inhalation significantly impairs both proximal and distal basilar dendritic ramifications (in the parietal and frontal/occipital cortices, respectively) and (ii) melatonin both protects neurons from toluene neurotoxicity in all cortical areas studied and increases the complexity of the dendritic tree above control values.
authors.affiliation: Laboratorio de Neurociencias, Escuela de Kinesiología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2950, Valparaíso, Chile. rodrigo.pascual@ucv.cl
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Pascual
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustamante
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000473:pathology; D003712:Dendrites / Q000187:drug effects* / Q000473:pathology; D005260:Female; D008297:Male; D008550:Melatonin / Q000494:pharmacology* / Q000627:therapeutic use; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000633:toxicity; D017966:Pyramidal Cells / Q000187:drug effects* / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012997:Solvents / Q000633:toxicity; D014050:Toluene / Q000037:antagonists & inhibitors* / Q000633:toxicity; D014835:Volatilization
chemical_list: D018696:Neuroprotective Agents; D009498:Neurotoxins; D012997:Solvents; D014050:Toluene; D008550:Melatonin