The significance of dendritic release of transmitter and protein in the substantia nigra.

The transmitter dopamine and the protein acetylcholinesterase are released within the substantia nigra from the dendrites of nigrostriatal neurons. These phenomena do not correspond to the familiar events involved in information transfer at the classic axons synapse. It is possible that both dopamine and acetylcholinesterase, released in the substantia nigra, are acting in a novel, perhaps synergistic, fashion as "neuromodulators". A hypothetical mechanism of neuromodulation by dendritically released material is discussed, in the light of recent findings on the morphology and physiology of nigrostriatal neurons.