Neuroendocrine Parvocellular Neurons

Abstract

Two sets of neuroendocrine neurons in the hypothalamus form a critical interface between the nervous and the endocrine systems. Neuroendocrine magnocellular neurons that release oxytocin and vasopressin from the neural lobe of the pituitary gland into the general vasculature constitute one of these sets; neuroendocrine parvocellular neurons comprise the other. These neurons release chemical signals into the hypophysial portal vasculature that then control the release of hormones from the anterior pituitary gland. These neurons form part of the neural network that generates pulsatile hormone release. However, more complex patterns of neuroendocrine release are enabled by more widely sourced neural afferents. In some cases, they are direct targets of feedback control by the hormones whose release neuroendocrine parvocellular neurons ultimately control.

Key Concepts:

  • Neuroendocrine parvicellular neurons release chemical signals (releasing factors) directly into the hypophysial portal vasculature.

  • Most of the body's hormones are released in pulsatile manner.

  • Feedback control of neuroendocrine activity is a key regulatory feature for neuroendocrine parvicellular neurons.

  • The brain contains complex neural networks that can influence the activity patterns of neuroendocrine parvicellular neurons.

Keywords: peptides; steroid hormones; afferent control; neural networks; feedback; hypothalamus

Figure 1.

Diagram showing the location of parvocellular neuroendocrine neurons in the hypothalamus (red dots). The distribution of the neurons that contain the various releasing controlling substances is also shown. The distribution of nuclei is based on the flat map from Swanson . ADP, anterodorsal preoptic nucleus; AHA, anterior hypothalamic area; AHN, anterior hypothalamic nucleus; AVP, anteroventral preoptic nucleus; AVPV, anteroventral periventricular nucleus; CRH, corticotrophin‐releasing hormone; DA, dopamine; DMH, dorsomedial nucleus; GHRH, growth hormone‐releasing hormone; GnRH, gonadotrophin‐releasing hormone; LPO, lateral preoptic area; MEPO, median preoptic nucleus; MPN, medial preoptic nucleus; MPO, medical preoptic area; PD, posterior dorsal nucleus; PMd, dorsal premammillary nucleus; PMv, ventral premammillary nucleus; PS, parastrial nucleus; PSCH, perisuprachiasmatic nucleus; PV, periventricular nucleus; PVHd, paraventricular nucleus, dorsal parvocellular division; PVHm, paraventricular nucleus, magnocellular division; PVHp, paraventricular nucleus, parvocellular division; RCH, retrochiasmatic area; SBPV, subparaventricular zone; SCH, suprachiasmatic nucleus; SO, supraoptic nucleus; SS, somatostatin; TRH, thyrotrophin‐releasing hormone; TU, tuberal nucleus and VMH, ventromedial nucleus.

Figure 2.

Organisation of the blood supply to the rat anterior pituitary gland. (a) Ventral aspect and (b) dorsal aspect. Rostral is the top of the diagram in both cases. IP, infundibular process of the neurohypophysis and PD, pars distalis of the pituitary gland. From Daniel and Prichard .

Figure 3.

Ovulation in the rat is triggered by a massive increase in gonadotrophin‐releasing hormone (GnRH) release into the portal vasculature from neuroendocrine terminals in the median eminence. The lower panel shows GnRH in hypophysial portal plasma; the upper panel shows the surge of luteinising hormone (LH) in peripheral plasma. From Sarkar et al. .

Figure 4.

Photomicrographs of corticotrophin‐releasing hormone (CRH) immunoreactivity at the level of the hypothalamic paraventricular nucleus (PVH) and median eminence. (a) Low‐power photomicrograph of the PVH showing neuroendocrine neurons in the PVH. Their axons leave the PVH in a lateral direction, curve around the fornix (fx), first ventrally and then caudally (not shown) to reach the median eminence. (b) Higher power photomicrograph of CRH‐immunoreactive neurons in the PVH. Note the relatively simple, generally fusiform, morphology of the cell body, and the two, sometimes three, dendrites. (c) Photomicrograph at the same scale as (b). Note the intense immunoreactivity in CRH axons and terminals in the median eminence, particularly in its ventral aspect. 3V, third ventricle and och, optic chiasm.

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Further Reading

Markakis EL and Swanson LW (1997) Spatiotemporal patterns of secretomotor neuron generation in the parvocellular neuroendocrine system. Brain Research. Brain Research Reviews 24: 255–291.

Sudhof TC (2004) The synaptic vesicle cycle. Annual Review of Neuroscience 27: 509–547.

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Ulrich‐Lai YM and Herman JP (2009) Neural regulation of endocrine and autonomic stress responses. Nature Reviews. Neuroscience 10: 397–409.

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How to Cite close
Watts, Alan G(Sep 2010) Neuroendocrine Parvocellular Neurons. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000047.pub2]