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

Abstract

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.

Model Roles of the Hypothalamo-Neurohypophysial System in Neuroscience Study

“…In addition, the SON also has the following important features: 1) A clear separation of the somatodendritic zone from the axon terminals, which allows separate studies on the release profile of neuropeptides in the brain and in the circulation; 2) A distinguished spatial orientation of astrocyte processes, which is suitable for observing glial-neuronal interactions at microdomain and molecular levels; 3) Coexpression of classical neurotransmitters with neuropeptides, which provides a model to observe the interactions between different types of neurotransmitters in the autoregulation of MNC activity, and 4) Dependence of release patterns of the blood neuropeptides on their intranuclear release and on the activity of decomposing enzyme. After the initial findings, these features are also identified in many other types of neurons, particularly neuroendocrine cells [4,5]. Therefore, the SON remains a "model system" in our pursuing neuroscience research.…”

Oxytocin and Migraine Headache

“…Oxytocin is synthesized in magnocellular neurosecretory cells in both the supraoptic and paraventricular nuclei of the hypothalamus . From these cells, some oxytocin is stored in Herring bodies at the axon terminals of the posterior pituitary and released into the blood from the posterior lobe (neurohypophysis) of the pituitary gland . In addition, some paraventricular neurons project directly to several other brain areas as well as the dorsal horn of the spinal cord .…”

“…3 From these cells, some oxytocin is stored in Herring bodies at the axon terminals of the posterior pituitary and released into the blood from the posterior lobe (neurohypophysis) of the pituitary gland. 4 In addition, some paraventricular neurons project directly to several other brain areas as well as the dorsal horn of the spinal cord. 5 Neurons in numerous brain and spinal cord regions have been shown to possess oxytocin receptors, including dorsal root and trigeminal ganglia neurons, 6,7 suggesting a role in pain modulation.…”

Communication Impairment in Ultrasonic Vocal Repertoire during the Suckling Period of Cd157 Knockout Mice: Transient Improvement by Oxytocin

“…OXT release from the soma, dendrites, and axon terminals of hypothalamic neurons occurs in response to intracellular Ca 2+ mobilization (Amina et al, 2010; Lopatina et al, 2010; Leng et al, 2015; Higashida, 2016). This mechanism is regulated by activity of ADP-ribosyl cyclase CD38, a multifunctional molecule that combines enzymatic and receptor properties, and plays a key role in OXT secretion, critically regulating maternal and social behavior in mice (Jin et al, 2007; Salmina et al, 2010; Lee, 2011; Mushtaq et al, 2011; Schmid et al, 2011).…”