Adhesion molecules and structural plasticity of the adult hypothalamo-neurohypophysial system

The adult hypothalamo-neurohypophysial system, responsible for the secretion of the neurohormones, oxytocin, and vasopressin, undergoes reversible neuronal-glial and synaptic changes in response to stimulation (parturition, lactation, and osmotic stimulation). In the hypothalamus, these changes result in reduced astrocytic coverage of oxytocinergic somata and dendrites and concomitant increases in their GABAergic synapses; in the neurohypophysis, they lead to an enlarged neurovascular contact area. We discuss the possible role played by certain cell adhesion molecules, such as the highly sialylated isoform of the neural cell adhesion molecule, PSA-NCAM, the F3 glycoprotein, and the extracellular matrix molecule, tenascin, in such plasticity. The hypothalamo-neurohypophysial system continues to express high levels of these molecules during adulthood and they may serve as permissive factors to allow stimulus-induced structural remodelling to occur.