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Dopaminergic pathways (dopamine pathways, dopaminergic projections) in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. [1] Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.
The mesolimbic pathway and its positioning in relation to the other dopaminergic pathways. The mesolimbic pathway is a collection of dopaminergic (i.e., dopamine-releasing) neurons that project from the ventral tegmental area (VTA) to the ventral striatum, which includes the nucleus accumbens (NAcc) and olfactory tubercle. [9]
The substantia nigra is located in the ventral midbrain of each hemisphere. It has two distinct parts, the pars compacta (SNc) and the pars reticulata (SNr). The pars compacta contains dopaminergic neurons from the A9 cell group that forms the nigrostriatal pathway that, by supplying dopamine to the striatum, relays information to the basal ganglia.
In the direct pathway, the motor cortices send activating signals to the caudate and putamen (which together form the dorsal striatum). The cells of the direct pathway in the caudate and putamen that receive these signals are inhibitory and, once they become activated, send inhibitory signals to the GPi and SNpr and stop activity there.
This results in loss of normal action selection, as loss of dopamine drives activity in the indirect pathway, globally inhibiting all motor paradigms. This may explain impaired action initiation, slowed actions ( bradykinesia ), and impaired voluntary motor initiation in Parkinson's patients.
Neurochemical studies have shown that BSR results in the release of dopamine within the nucleus accumbens. [21] This effect is generally potentiated following administration of drugs that themselves increase the amount of extracellular dopamine in the nucleus accumbens, such as cocaine , which inhibits re-uptake of dopamine to the intracellular ...
The indirect pathway is responsible for the termination of movement. The indirect pathway inhibits unwanted movements by simultaneous increase in excitatory input to other GPi and SNr neurons. [4] Similar to the direct pathway, the indirect pathway is regulated by striatal dopamine. D 2 dopamine receptors inhibit transmission via the indirect ...
As the pathway from the striatum to the medial globus pallidus is monosynaptic (containing one synapse), it is called the direct pathway. The indirect pathway, which contains the GPe and the subthalamic nucleus, functions to modulate the effects of the direct pathway. The GPe acts as an inhibitory "control device", adjusting subthalamic nucleus ...