Thorium-induced neurobehavioural and neurochemical alterations in Swiss mice.
OBJECTIVE
Thorium ((232)Th), a heavy metal radionuclide that targets the liver and skeleton, has been shown to accumulate in the central nervous system at low levels. The present study was aimed to investigate neurobehavioural and neurochemical changes in mice treated with (232)Th at sub-lethal doses.


METHODS
Swiss albino mice were administered intraperitoneally with thorium nitrate. The chelation-based therapeutic effect of calcium diethylenetriamine pentaacetate (Ca-DTPA) was tested on the (232)Th-treated mice. (232)Th localisation was determined in brain regions by the Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. Achetylcholine esterase (AChE) activity in different brain regions was evaluated to assess the cholinergic function of mice CNS. Oxidative damage was evaluated by assessing the activities of antioxidant enzymes (i.e., superoxide dismutase and catalase) and the level of lipid peroxidation. The neurobehavioural alteration in the treated mice was studied by the shuttle box method.


RESULTS
(232)Th accumulation found in different brain regions followed the order: Cerebellum (Cbl) > cortex (Ctx) > hippocampus (Hp) > striatum (Str). However, removal of (232)Th by Ca-DTPA was significant from brain regions like Cbl, Ctx and Str but not from Hp. A significant increase in lipid peroxidation and acetylcholine esterase (AChE) activity was observed in the treated mice but activities of superoxide dismutase and catalase was found substantially decreased. (232)Th treatment impaired the learning and memory-based neurobehaviour of the mice. Furthermore, our data suggest that Ca-DTPA injection in (232)Th-treated animals failed to improve the neurobehaviour of the treated mice, perhaps because Ca-DTPA could not decorporate (232)Th or mitigate (232)Th-mediated neurochemical changes effectively from/in hippocampus, a brain region implicated in learning and memory response.


CONCLUSIONS
Administration of (232)Th in mice caused neurobehavioural alteration and impairment of cholinergic function, which might be the consequence(s) of oxidative stress induction in different brain regions.
Kumar
Amit
A
Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, India.
Ali
Manjoor
M
Mishra
Pravin
P
Pandey
B N
BN
Sharma
Pragya
P
Mishra
Kaushala Prasad
KP
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001362:Avoidance Learning / Q000187:drug effects / Q000528:radiation effects; D001522:Behavior, Animal / Q000187:drug effects* / Q000528:radiation effects; D001692:Biological Transport; D001835:Body Weight / Q000187:drug effects / Q000528:radiation effects; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D002490:Central Nervous System / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D007267:Injections; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects; D051379:Mice; D009448:Neurochemistry; D004369:Pentetic Acid / Q000494:pharmacology; D013910:Thorium / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity*; D017970:Thorium Compounds / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity
D000975:Antioxidants; D017970:Thorium Compounds; D013910:Thorium; D004369:Pentetic Acid; D000110:Acetylcholinesterase; C036680:thorium nitrate