[Pineal body in vertebrates: a model for investigations of receptor and effector mechanisms of neuronal systems].

Cell and molecular biological investigations have greatly contributed to our understanding of receptor and effector mechanisms in sensory, neuronal, and endocrine cells. A fascinating aspect of this line of research is how such mechanisms have evolved and how they interact with each other. As shown in this contribution, the vertebrate pineal organ is an interesting model to study these problems, because it undergoes a conspicuous transformation during phylogeny, comprises two well-characterized receptor mechanisms (photoreception and adrenoreception), and acts upon its targets via neuronal and neuroendocrine signals.