Figure 17. Diagrammatic representation of a parasagittal view of the rat brain, illustrating the VIP chemistry of the hypothalamic/pituitary system. VIP neurons (blue) are shown projecting from the paraventricular and supraoptic hypothalamic nuclei to the median eminence, where terminals abut the primary capillary plexus of the pituitary portal system. Additional terminals are found in the posterior pituitary, where VIP can potentially be released into the systemic circulation. Some VIP fibers and terminals in the portal circulation may originate in the periphery and function to regulate vasodilation of portal vessels. VIP cells are also shown in the pituitary, where they may regulate anterior pituitary function in an autocrine or paracrine fashion. VIP binding (red) is shown, with the intensity of the color representing the density of VIP binding.