Pharmacological Modulation of Dopaminergic Brain Activity and Its Reflection in Spectral Frequencies of the Rat Electropharmacogram

Background: Particular frequencies of electropharmacograms have been attributed to cholinergic, noradrenergic or dopaminergic mediated neurotransmission. This investigation deals with changes induced by L-DOPA or dopamine D2 receptor agonists. Method: Adult rats (day-night converted) were instrumented with four bipolar concentric semi-micro-electrodes into the frontal cortex, hippocampus, striatum and reticular formation. Field potentials were recorded during a pre-drug reference period followed by 4 h of recording thereafter. Data were transmitted wirelessly for spectral frequency analysis. Results: At low doses of L-DOPA (1-5 mg kg(-1)) and of the D2 agonists talipexole and quinpirole (0.1 mg kg(-1)), a delayed increase of delta and theta power was observed. Higher doses led to immediate stable decreases of alpha1, alpha2 and beta1 power as reported for dopamine D1 receptor agonists. Administration of the D2 blocker sulpiride (10-20 mg kg(-1)) resulted in increases of alpha2 power. Conclusion: A common denominator for changes of dopaminergic transmission could be seen in immediate changes of spectral alpha2 power. Delayed increases of delta and theta activity after low dosages of the medication are considered to originate from heterosynaptic, presynaptic D2 receptors sitting on cholinergic neurons. This pattern could explain daytime tiredness or sudden sleep attacks in Parkinson patients. Copyright (c) 2009 S. Karger AG, Basel