Circumventricular organs: receptors and mediators of direct peptide hormone action on brain.

The concept of the brain as an endocrine target organ is not new, nor is it novel to consider the circumventricular organs as receptive regions of the brain for circulating substances. However, in this review we have emphasized the relatively novel concept that CVOs mediate exclusively the direct feedback actions of circulating peptide hormones on brain function. In addition we have presented speculations concerning the neural mechanisms by which signals arising from peptide hormone-receptor interaction might be relayed into the CNS, and indicated the possible involvement of CVO receptors in endocrine disorders. We hope that this analysis provides a conceptual framework for evaluating the functional relationship of circulating peptides to brain and inspires interest in this fascinating area of neuroendocrinology.