EN
Our knowledge about the dopaminergic system is very wide. It includes both a myriad of minor facts as well as many milestone findings. This knowledge is the basis of theories created and the fuel for further research. However, in view of the increasing complexity of the emerging image of the dopaminergic system, we should verify whether some of the facts that have been taken for granted for decades are not too simplistic. As an example, I will present two observations recently made in our laboratory. First, the bursting pattern of firing of some dopaminergic neurons does not appear to be dependent on NMDA receptors. There is a population of dopamine (DA) neurons that, in response to the stimulation of cholinergic receptors, shift to a bursting mode of firing. The slow dynamics of the observed phenomenon suggest that it may be the basis of dopamine-dependent maintenance of the prolonged states of increased motivation of the animal. The second observation shows that DA neurons can dynamically change both the parameters and the direction of response to the arriving stimuli, depending on the general state of the brain. Thus, the assumption that DA neurons react stereotypically, with inhibition or excitation to a certain type of stimuli (e.g., aversive sensory), may be too simplistic. When we are dealing with a neural system with such a heterogeneous structure, we should seek to clarify some of our observations in this diversity, instead of trying to adapt to existing knowledge, which is often limited to a homogeneous, simplified image of the dopaminergic system.