Melatonin promotes distal dendritic ramifications in layer II/III cortical pyramidal cells of rats exposed to toluene vapors.
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.
Pascual
Rodrigo
R
Laboratorio de Neurociencias, Escuela de Kinesiología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2950, Valparaíso, Chile. rodrigo.pascual@ucv.cl
Bustamante
Carlos
C
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
D018696:Neuroprotective Agents; D009498:Neurotoxins; D012997:Solvents; D014050:Toluene; D008550:Melatonin