Long-term exposure to dieldrin reduces gamma-aminobutyric acid type A and N-methyl-D-aspartate receptor function in primary cultures of mouse cerebellar granule cells.
The organochlorine pesticide dieldrin is a persistent organic pollutant that accumulates in the fatty tissue of living organisms. In mammals, it antagonizes the GABA(A) receptor, producing convulsions after acute exposure. Although accumulation in human brain has been reported, little is known about the effects of long-term exposure to dieldrin in the nervous system. Homeostatic control of the balance between excitation and inhibition has been reported when neuronal activity is chronically altered. We hypothesized that noncytotoxic concentrations of dieldrin could decrease glutamatergic neurotransmission as a consequence of a prolonged reduction in GABA(A) receptor function. Long-term exposure of primary cerebellar granule cell cultures to 3 microM dieldrin reduced the GABA(A) receptor function to 55% of control, as measured by the GABA-induced (36)Cl(-) uptake. This exposure produced a significant reduction (approximately 35%) of the NMDA-induced increase in [Ca(2+)](i) and of the [(3)H]MK-801 binding, which was not accompanied by a reduction in the NMDA receptor subunit NR1, as determined by Western blot. Consistent with the decreased NMDA receptor function, dieldrin-treated cultures were insensitive to an excitotoxic stimulus induced by exposure to high potassium. In summary, we report that the chronic reduction of GABA(A) receptor function induced by dieldrin decreases the number of functional NMDA receptors, which may be attributable to a mechanism of synaptic scaling. These effects could underlie neural mechanisms involved in cognitive impairment produced by low-level exposure to dieldrin.
Babot
Zoila
Z
Department of Neurochemistry and Neuropharmacology, Institut d'Investigacions Biomèdiques de Barcelona, Consejo Superior de Investigaciones Científicas, CSIC-IDIBAPS, Rosselló 161, Barcelona, Spain.
Vilaró
M Teresa
MT
Suñol
Cristina
C
D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000187:drug effects* / Q000378:metabolism; D004026:Dieldrin / Q000633:toxicity*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004334:Drug Administration Schedule; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006843:Hydrocarbons, Chlorinated / Q000633:toxicity; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D007306:Insecticides / Q000633:toxicity; D051379:Mice; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity; D011188:Potassium / Q000633:toxicity; D011940:Receptor Aggregation / Q000187:drug effects / Q000502:physiology; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors
D006843:Hydrocarbons, Chlorinated; D007306:Insecticides; D009498:Neurotoxins; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D004026:Dieldrin; D011188:Potassium