2012
Volume 12, Number 4, pp. 158–160
Does manganese excess induce the mouse-killing behaviour in initially nonaggressive rats?
I.L. Lazrishvili, T.Z. Bikashvili, L. Gelazonia and V. Okuneva
Department of Neuroanatomy, I.Beritashvili Centre of Experimental Biomedicine, 14 Gotua St, 0160 Tbilisi, Georgia
Excessive aggression is attributed to social factors. Along with this, it is generally accepted that aggression and violent behavior may stem from toxic metals. There is evidence that the manifestations of aggressive behaviour may also be caused by an excess of manganese but data on the correlation between aggressive, violent manifestations and the level of manganese is mainly indirect and sometimes even contradictory. Hence, the effects of 30 day exposure to different doses of MnCl2 (10 and 15 mg/mL in drinking water) on the mouse killing behaviour (MKB) of rats was studied. Each rat was placed in an observation cage 5 min before the MKB test to allow it to accommodate to the cage. Then a naïve mouse was placed in the cage with the rat and the following parameters of the rat’s behaviour recorded for 3 min: (1) nonaggressive attack; (2) MKB (attempt); (3) MKB (successful killing). To eliminate spontaneously aggressive animals from subsequent experiments, rats were preliminarily tested for MKB. 30-day exposure to 10 mg/mL manganese does not stimulate aggressive behaviour in rats, while after exposure to the higher dose (15 mg/mL) 37% of initially nonaggressive animals manifested MKB and 25% attempted MKB. The data support the hypothesis that excess manganese in the body is one of the immediate causes of enhancement of interspecific predatory aggressive and violent behaviour in rats.
Keywords: manganese, mouse killing behaviour, rat, short-term exposure