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Concentrations of striatal catecholamines in rats given manganese chloride through drinking water
Abstract:
Male albino rats were exposed to manganese through drinking solution containing MnCl2 . 4H2O (1 mg/ml) in water. The contents of catecholamines, homovanillic acid, manganese and the activity of monoamine oxidase (MAO) were measured in the corpus striatum at different time intervals up to a period of 360 days. The contents of tyrosine in the corpus striatum and serum were also estimated. Manganese treatment produced an initial increase in the contents of dopamine (DA), norepinephrine (NE), homovanillic acid (HVA) and tyrosine in the corpus striatum. This was followed by a period when concentrations were almost normal (dopamine from 120 to 240 days, norepinephrine at 180 and 240 days and homovanillic acid at 240 days after manganese administration). Thereafter the contents of these substrates declined significantly at 300 and 360 days of treatment. However, these alterations were not correlated with the concentrations of manganese in this region, which gradually increased up to 240 days, and thereafter remained constant until the termination of the experiment. The underlying biochemical mechanisms of manganese-induced sequential changes in the striatal contents of catecholamines have been discussed in relation to the development of psychiatric and neurological phases of manganese poisoning.
Insights
Manganese exposure in rats initially increased dopamine and norepinephrine but later caused significant declines in these neurotransmitters, independent of manganese levels in the brain. These findings offer insights into manganese poisoning mechanisms.
Area of Science:
- Neuroscience
- Toxicology
- Biochemistry
Background:
- Manganese is an essential trace element, but excessive exposure can lead to neurotoxicity.
- Manganese poisoning is associated with psychiatric and neurological symptoms, yet the underlying biochemical mechanisms remain incompletely understood.
Purpose of the Study:
- To investigate the long-term effects of manganese exposure on catecholamine levels and monoamine oxidase activity in the rat corpus striatum.
- To correlate changes in catecholamine metabolism with manganese accumulation in the brain.
Main Methods:
- Male albino rats were administered manganese chloride (MnCl2·4H2O) in drinking water (1 mg/ml) for up to 360 days.
- Levels of dopamine (DA), norepinephrine (NE), homovanillic acid (HVA), tyrosine, and manganese were measured in the corpus striatum.
- Monoamine oxidase (MAO) activity was also assessed in the corpus striatum.
Main Results:
- Manganese treatment initially elevated striatal dopamine, norepinephrine, homovanillic acid, and tyrosine.
- These levels normalized temporarily before declining significantly at 300 and 360 days.
- Striatal manganese concentrations increased initially and then plateaued, showing no direct correlation with catecholamine alterations.
Conclusions:
- Manganese exposure induces sequential changes in striatal catecholamine metabolism, characterized by an initial rise followed by a significant decline.
- The observed biochemical alterations are not directly correlated with manganese accumulation in the corpus striatum.
- These findings contribute to understanding the neurochemical basis of manganese poisoning and its associated neurological and psychiatric manifestations.