[Localization of dopamine receptors on nerve cell membranes]

Experiments on rabbits anesthetized with urethane and chloralose were made to study the effect of microiontophoretically applied dopamine (DA) and immobilized DA connected with a polymer (DA-P) on extracellularly recorded activity of sensorimotor cortical neurons. Both DA-P and low-molecular DA reduced the frequency of spontaneous action potentials in the majority of the examined neurons in a dose-dependent manner. The inhibitory effect of DA-P was less powerful than that of DA under the same conditions of microiontophoretic application. Since low-molecular DA included in the structure of DA-P does not penetrate the neuron, it is concluded that the specific inhibitory effect of DA on neuronal activity is determined by its interaction with receptors located on the external surface of the neuronal membrane.