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Alterations in the biochemical properties of central dopamine synapses following chronic postnatal PbCO3 exposure
Insights
Chronic low-level lead exposure in rat pups caused hyperactivity and altered dopamine synapse function. This study investigated lead
Area of Science:
- Neuroscience
- Environmental Toxicology
- Developmental Biology
Background:
- Chronic low-level lead (Pb) exposure can impact neurodevelopment and behavior.
- Previous studies suggest Pb exposure affects locomotor activity.
- The precise biochemical mechanisms underlying Pb-induced behavioral changes at central dopamine (DA) synapses remain unclear.
Purpose of the Study:
- To investigate the pre- and postjunctional biochemical alterations at central dopamine synapses following chronic low-level lead exposure in developing rats.
- To correlate observed behavioral changes with specific neurochemical modifications in the brain.
Main Methods:
- Rat pups were chronically exposed to 40 ppm of lead from birth.
- Behavioral assessments included spontaneous and stimulant-induced locomotor activity.
- Biochemical analyses involved measuring neurotransmitter release and receptor-mediated enzyme activity in brain tissue.
Main Results:
- Pb-exposed rat pups exhibited hyperactivity but showed attenuated responses to amphetamine and apomorphine.
- Biochemical studies revealed diminished potassium-evoked release of exogenous [3H]dopamine from brain slices.
- Suppression of dopamine receptor-mediated activation of adenylate cyclase was observed in neostriatal homogenates.
Conclusions:
- Chronic low-level lead exposure induces significant pre- and postjunctional biochemical changes at central dopamine synapses.
- These neurochemical alterations likely contribute to the observed Pb-induced changes in locomotor activity.
- The findings provide insights into the neurobiological mechanisms of lead neurotoxicity during development.
Abstract:
Behavioral studies on spontaneous and stimulant-induced locomotor activity after chronic low-level lead (Pb) exposure prompted us to investigate the pre- and postjunctional biochemical properties at central dopamine (DA) synapses. Rat pups were chronically exposed from birth to 40 ppm of Pb and tested behaviorally and biochemically at 25 to 35 days of age. Pb-exposed rat pups demonstrated locomotor hyperactivity, but the locomotor response to d-amphetamine SO4 (0.5-2.0 mg/kg) or apomorphine HCL (0.5-5.0 mg/kg) was attenuated. Correlative biochemical studies in rat brain tissue demonstrated associated pre- and postjunctional changes at central DA synapses. These biochemical changes included 1) diminished KC-evoked release of exogenous [3H]DA from brain slices, and 2) suppression of the DA receptor-mediated activation of adenylate cyclase in neostriatal homogenates. No changes were observed in the synthesis, accumulation of d-amphetamine-induced release of radiolabeled DA in brain tissue from these animals. These results are discussed in relation to the possible mechanisms associated with Pb-evoked neurochemical changes as well as the role that each of these effects may play in the Pb-induced alterations of locomotor activity.