Ultrastructure of hypothalamic paraventricular neurons.

The hypothalamic paraventricular nucleus (PVN) plays a pivotal role in the regulation of endocrine processes and the modulation of autonomic functions. The multi-channel outputs of the nucleus are directed toward the anterior and posterior lobes of the pituitary, autonomic centers, and limbic structures. Counterbalancing the wide spectrum of efferent projections, the nucleus receives humoral signals from endocrine glands and neuronal afferents from several loci of the brain. The multiple functions of the nucleus are executed by neurons that are organized in distinct subnuclei and display complex chemotypes. The review demonstrates and discusses the organization, architecture, chemical composition, plasticity, and pathology of paraventricular neurons of the rat hypothalamus from the perspective of ultrastructural analysis. Electron microscopy--by its high resolution--offers a powerful tool that is suitable for revealing the structural background of physiological processes that modulate and govern the operation of paraventricular neurons.