title: Protective role of noradrenaline in benzo[a]pyrene-induced learning impairment in developing rat.
abstract: Benzo[a]pyrene (B[a]P), a carcinogen, affects brain development, learning, and memory. Isolated studies have reported that B[a]P elevates noradrenaline (NA) level that may modulate neuronal growth, learning, and memory. Therefore, we investigated in vivo and in vitro the effects of B[a]P on learning and memory and its possible mechanism of action. Intracisternal administration of B[a]P on postnatal day 5 significantly reduced learning and memory in adolescent rats as observed by probe test using the Morris water maze. The density of both the subunits of the N-methyl-D-aspartate (NMDA) receptor, NMDAR1 and NMDAR2B, significantly increased in the hippocampus. In vitro, B[a]P significantly increased NMDAR1 in both C6 and Neuro2a cell lines, whereas NMDAR2B was significantly increased in C6 but was significantly decreased in Neuro2a. Pretreatment with NA prevented the B[a]P-induced effect on NMDAR1 expression in both cell lines. However, although NA prevented the B[a]P-mediated increase in NMDAR2B expression in C6, it further potentiated the decrease of NMDAR2B in Neuro2a cells. Also, NA prevented the B[a]P-induced increase in intracellular Ca(2+) both in C6 and in Neuro2a. Our findings show that postnatal exposure of developing rats to B[a]P impairs learning and memory even when the rats became adolescent. We also observed that the effects were mediated by elevated intracellular Ca(2+) levels and increased expression of NMDAR; furthermore, NA exerted a protective effect by modulating those factors. NA differentially affects neurons and glia, which may have a compensatory role during toxic insults, especially from B[a]P.
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Manorama
authors.initials: M
authors.lastname: Patri
authors.forename: Abhishek
authors.initials: A
authors.lastname: Singh
authors.forename: Birendra Nath
authors.initials: BN
authors.lastname: Mallick
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002273:Carcinogens / Q000633:toxicity*; D007150:Immunohistochemistry; D007858:Learning / Q000187:drug effects*; D008297:Male; D008568:Memory / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002273:Carcinogens; D001564:Benzo(a)pyrene; D009638:Norepinephrine
keywords: NMDA receptor subunits; brain development; calcium; carcinogen; intracisternal injection; neuron-glia interaction; neurotoxicity