Biochemical changes in the rat cerebellar cortex elicited by chronic treatment with methyl mercury

Mercury exposure and neurochemical impacts in bald eagles across several Great Lakes states

“…With GAD, we found a significant association with IHg, but not with OHg or THg. Results of previous in vivo studies vary, with some showing no effect of Hg treatment on GAD activity (Tsuzuki 1981;Concas et al 1983) and others showing a decrease in activity (O'Kusky and McGeer 1985;O'Kusky et al 1988). However, these studies do not relate activity to brain levels of THg, OHg, or IHg.…”

“…When coupled with several studies demonstrating a similar Hg-associated decrease in NMDA receptors (Basu et al 2007b(Basu et al , 2009aScheuhammer et al 2008), our results help support the notion that the NMDA receptor is a sensitive indicator of Hg's earliest neurological effects. We found no relationship between Hg and GABA A receptor benzodiazepine receptors, which are known to increase with Hg exposure in rats (Concas et al 1983). We observed a slight, though significant increase in GS activity with brain THg levels.…”

“…Rodent studies show that Hg alters components of both pathways (Concas et al 1983;Rajanna et al 1997;Monnet-Tschudi et al 1996), but these effects are not well documented in birds. Because glutamate and GABA play roles in learning and coordination (Scholes 1965;Gibbs et al 2008), changes in components of these systems may disrupt ecologically important behaviors.…”

Assessing the neurotoxicological risk of methylmercury exposure for beluga whales (delphinapterus leucas) harvested in the Mackenzie Delta Estuary.

“…Gamma-butyric acid-A receptors have been linked to sedation, sleep, anxiety, seizures and amnesia (Vicini and Ortinski, 2004). The activity o f the GABAa-R is modulated by benzodiazepines (Chebib and Johnston, 1999), and drugs that enhance the function o f the benzodiazepine binding site result in symptoms very similar to symptoms o f MeHg toxicity, including ataxia, lack o f muscular incoordination, motor disturbance and decreased Purkinje cell activity (Concas et al, 1983). The negative relationship between GABAa receptor levels and Hgj and MeHg in the cerebellar cortex but not temporal cortex was consistent with findings from captive mink in which GABA-R binding to [3H]-Muscimol in cerebellum but not occipital cortex were negatively associated with dietary exposure to MeHg .…”

“…In acute MeHg feeding trials, MeHg-exposed rats had increased benzodiazepine binding sites, but not GABA binding sites in various brain regions (Concas et al, 1983;Corda et al, 1981). Methylmercury and iHg may disrupt GABAergic signaling through the inhibition o f GABA uptake by astrocytes, and the modulation o f GABAinduced inward currents (Arakawa et al, 1991;Narahashi et al, 1994).…”