5-Hydroxytryptamine receptors in neurones and glia.

Crude membranal fractions isolated from mammalian brain tissue contain two classes of recognition sites capable of binding [3H]5-HT with high affinity constants. These classes of sits are characteristics of the postsynaptosomal membrane fraction for the higher affinity and of a glial cell membrane fraction for the lowest. They are observed with similar properties in cultured neuronal and glial cell respectively. Two 5-HT stimulated adenylate cyclases are present in crude membrane fraction; they are also separable as neuronal and glial components. These observations correspond likely to the existence of two classes of receptors for 5-HT. Their mechanisms of regulation involve presumably structural conformation changes of the recognition site coupled to various states of the activity of the receptor.