Abstract
<jats:p>BACKGROUND: Our studies, as well as the work of other authors, have revealed a gradual decrease in phasic extracellular dopamine release after repeated stimulation of dopaminergic brain structures in experimental animals. This phenomenon is often overlooked by researchers because it falls outside the scope of their research goals and objectives. Some attribute it to fatigue, suggesting that the dopamine supply in the nerve endings does not have time to recover between stimulations. However, there is no scientific evidence to support this assumption. Alternatively, the reduction in phasic extracellular dopamine release may be attributed to habituation, one of the simplest forms of learning. In this context, habituation occurs within dopaminergic structures in response to monotonously repeated stimuli. AIM: The study aimed to substantiate the hypothesis by comparing the characteristics of decreased phasic releases of extracellular dopamine to the habituation characteristics described in previous publications. METHODS: We use publications, previously published data, and new results from our experiments to identify features associated with reducing phasic releases of extracellular dopamine. The experiments involved inducing phasic dopamine releases through electrical stimulation of dopaminergic nuclei in the rat brain. Recording was performed using fast-scan cyclic voltammetry. RESULTS: Experiment 1, conducted on anesthetized rats, confirmed that repeated stimulation results in a gradual decrease in phasic dopamine release in the nucleus accumbens core. Experiment 2, conducted on rat brain slices, identified the physiological mechanism responsible for habituation of phasic dopamine release from dopaminergic nerve fiber endings. Kinetic analysis revealed that habituation is caused by a decrease in dopamine released into the extracellular environment, rather than an increase in its reuptake. CONCLUSION: The decrease in phasic extracellular dopamine release when the brain's dopaminergic structures are stimulated repeatedly over several minutes, can be explained by habituation which is a physiological mechanism that decreases dopamine release at the endings of dopaminergic nerve fibers.</jats:p>