Through inhibition of reuptake, cocaine increases monoaminergic tone in the central nervous system.4 The activities of the neurons within the locus coeruleus play a pivotal role in central noradrenergic transmission and regulate overall levels of arousal and attention.3,10 We have found that cocaine in low concentrations (0.3-1.0 μM) induced slow oscillations (0.8 Hz) in membrane potential (2-6 mV). These oscillations were synchronized in neurons throughout the nucleus and were blocked by α2-adrenergic receptor antagonists. The synchrony of these events was thought to arise from within the nucleus, through a combination of spontaneous activity (intrinsic properties) 24 and noradrenergic mediated inhibitory postsynaptic potentials6,7 augmented by cocaine. The synchronous firing of noradrenergic neurons may facilitate transmitter release in the widespread projection areas and thus be important for the action of cocaine to increase levels of arousal.23.
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