Primary cultures of virtually pure striatal neurons from 16-day-old mouse embryos can be obtained using a serum-free chemically defined medium. Membranes prepared from these cells contain dopamine, beta-adrenergic, serotonin and adenosine sensitive adenylate cyclases. The pharmacological properties of the dopamine receptors are similar to those found for D1 receptors in adults except for the apparent affinities for agonists which were 5-10 times higher in fetal neurons. Beta-adrenergic receptors of striatal and cerebellar fetal neurons are of the beta 1-subtype as indicated by their identical affinity for adrenaline and noradrenaline and by their homogeneous, high affinity for practolol (Ki = 1.3 X 10(-6)M). Adenosine and serotonin sensitive adenylate cyclases present classical characteristics. An extensive study of the additive effects of the 4 neurotransmitter-sensitive adenylate cyclases indicates that: (1) part of the neurons bear more than one type of biogenic amine receptors; (2) the serotonin receptors are always associated with adenosine receptors on the same neurons; (3) adenosine- and dopamine-sensitive adenylate cyclases are additive. From this it can be concluded that as far as their adenylate cyclases-linked amine receptors are concerned, a maximal number of 15 types of neurons are present in these striatal cell cultures.