60 YEARS OF NEUROENDOCRINOLOGY: The posterior pituitary, from Geoffrey Harris to our present understanding

• Published in: Journal of endocrinology Vol. 226; no. 2; pp. T173 - T185
• Main Authors: Leng, Gareth, Pineda, Rafael, Sabatier, Nancy, Ludwig, Mike
• Format: Journal Article
• Language: English
• Published: England Bioscientifica Ltd 01-08-2015
• Subjects: Animals; Female; Humans; Milk Ejection - physiology; Oxytocin - physiology; Parturition - physiology; Pituitary Gland, Posterior - physiology; Thematic Review; Vasopressins - physiology; physiology; oxytocin; vasopressin; pitutitary
• ISSN: 0022-0795; 1479-6805
• DOI: 10.1530/JOE-15-0087

Geoffrey Harris pioneered our understanding of the posterior pituitary, mainly with experiments that involved the electrical stimulation of the supraoptico-hypophysial tract. In the present essay, we explain how his observations included clues to the pulsatile nature of the oxytocin signal – clues that were followed up by subsequent workers, including his students and their students. These studies ultimately led to our present understanding of the milk-ejection reflex and of the role of oxytocin in parturition. Discoveries of wide significance followed, including: the recognition of the importance of pulsatile hormone secretion; the recognition of the importance of stimulus-secretion coupling mechanisms in interpreting the patterned electrical activity of neurons; the physiological importance of peptide release in the brain; the recognition that peptide release comes substantially from dendrites and can be regulated independently of nerve terminal secretion; and the importance of dynamic morphological changes to neuronal function in the hypothalamus. All of these discoveries followed from the drive to understand the milk-ejection reflex. We also reflect on Harris's observations on vasopressin secretion, on the effects of stress, and on oxytocin secretion during sexual activity.