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Effect of organic mercury exposure during early stage of ontogenic development on the central dopaminergic system in adult rats

100%

Durczok A. , Szkilnik R. , Brus R. , Nowak P. , Labus L. , Konecki J. , Drabek K. , Kuballa G. , Rycerski W. , Mengel K.

2002

tom 11

nr 4

Organic mercury (CH3HgCl) with metal concentration 5 ppm in tap water was applied to rats suckling their newborn for the first 21 days of life. A second group of young rats took the mercury in their tap water 5 ppm from the 22nd to the 43rd day of postnatal life. Control rats drank tap water only. In 2-month-old male rats the following behavioral study was performed after saline or specific central dopamine receptor agonists and agonists apply (quinpirole, SKF-38393, haloperidol, SCH-23390): irritability, yawning behavior, oral activity, locomotion, exploratory activity, and catalepsy. In the striatum and frontal cortex of three examined groups the biogenic amines levels (DA, DOPAC, HVA, 3-MT, 5-HT, 5-HIAA, NA) were estimated by means of HPLC/ED technique, and DA and 5-HT turnover. The effect of quinpirole (a central dopamine D2 receptor agonists) was also examined on (3H)glucose uptake in discrete parts of the brain. It was shown that mercury affected behavioral changes after dopaminergic agents apply to adult animals when exposed in the period from the 22nd to 43rd day of postnatal development. Biochemical changes (biogenic amines level, turnover and (3H)glucose uptake) were more pronounced in adult animals exposed to mercury via mother's milk (1st to 21st day of life). In light of the above we conclude that early postnatal exposure of rats to organic mercury modulates activity of the central dopamine neurotransmitter system.

The effects of zinc on the central dopaminergic system of rats prenatally exposed to cadmium

80%

Durczok A. , Szkilnik R. , Nowak P. , Labus L. , Dabrowska J. , Bortel A. , Zagzil T. , Swoboda M. , Rycerski W. , Winnicka H. , Kostrzewa R. M. , Kwiecinski A. , Brus R.

nr 5

On the morning of the first day of pregnancy, Wistar rats were administered a single IP injection of either zinc sulfate (10.0 mg/kg) or saline. For the remainder of pregnancy, half the rats in each group then consumed filtered tap water while the other half consumed filtered tap water with 50 ppm of cadmium (CdCl₂ ). At eight weeks after birth, the behavioral profile of male offspring was assessed in the following way: Apomorphine (non-selective dopamine receptor agonist), (+)-7-hydroxy-2-(di-n-propylamino) tetralin (7-OH-DPAT) (D₃ agonist) and (+/-)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol (SKF 38393) (D₁ agonist) were used to evaluate stereotyped behavior, yawning activity and oral movements – indices for these respective agonists. In addition, two dopamine receptor antagonists, haloperidol (D₂ antagonist) and 7-chloro-8-hydroxy3-methyl-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzapine (SCH 23390) (D₁ antagonist) were used to evaluate cataleptogenic activity. Additional behavioral parameters studied were locomotor activity, irritability and reaction to a painful stimulus. Dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 3-methoxytyramine (3-MT) were quantified in the striatum, hippocampus and in the frontal cortex of the brain by means of HPLC/ED technique. In addition, cadmium levels were analyzed in the brain, liver, kidney and bone of newborn rats. Our results indicate that prenatal exposure of pregnant rats to cadmium produced alterations in the reactivity of central dopamine receptors and modulated the level of dopamine and its metabolites in the offsprings’ brains. A single injection of zinc, preceding cadmium consumption, attenuated some of the effects of cadmium on the offsprings’ dopaminergic system. Zinc also reduced cadmium deposition in the brain, kidney and bone, but enhanced its accumulation in liver. In summary, zinc may exert some neuroprotective effects against cadmium neurotoxicity.