Two types of dopamine receptors in behavioral regulation.

Evidence has been presented indicating the existence of distinct dopamine receptors in the brain. The experimental proof that two types of dopamine receptors--the excitation-mediating (DAe) receptors and the inhibition-mediating (DAi) receptors--exist in the snail brain is put forward. The functioning of DAi and DAe receptors in locomotor activity and stereotyped behavior is discussed along with implications of dopaminergic involvement in a gratification system.