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Interleukin‐1β immunoreactivity in identified neurons of the rat magnocellular neurosecretory system: Evidence for activity‐dependent release
Author(s) -
Watt John A.,
Hobbs Nicole K.
Publication year - 2000
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(20000515)60:4<478::aid-jnr6>3.0.co;2-r
Subject(s) - median eminence , hypothalamus , biology , magnocellular cell , immunocytochemistry , medicine , endocrinology , oxytocin , immunoelectron microscopy , posterior pituitary , supraoptic nucleus , vasopressin , neuroscience , pituitary gland , immunohistochemistry , hormone , immunology
Interleukin‐1β has been demonstrated in neurons of the rat hypothalamus, including cells of the magnocellular neurosecretory system and tuberoinfundibular system (Lechan et al., [1990] Brain Res. 514:135–140). Despite its potential importance to regulation of neuroendocrine function, however, neither the specific cell types that express interleukin‐1β or the conditions that may result in its release have yet been described. Therefore, we utilized a combination of immunocytochemical and immunoelectron microscopic localization, in conjunction with Western blot analysis, on normonatremic, hypernatremic, and lactating rats to assess the site of synthesis and potential secretion characteristics of interleukin‐1β in the rat magnocellular neurosecretory system. Interleukin‐1β immunoreactivity was localized within both oxytocin and vasopressin neurons in the paraventricular, supraoptic, accessory and periventricular hypothalamic nuclei. Additionally, interleukin‐1β immunoreactive fibers were localized in the zona interna and zona externa of the median eminence and in the neurohypophysis. Immunoelectron microscopic analysis revealed that interleukin‐1β immunoreactivity is associated with small spherical structures, distinct from neurosecretory granules, in neurosecretory axons within the neurohypophysis. Furthermore, stimulation of heightened neurosecretory activity via chronic osmotic challenge and lactation resulted in a marked diminution in levels of interleukin‐1β immunoreactivity in the neurohypophysis with a subsequent return to normal levels after cessation of the stimuli. Western blot analysis confirmed the existence of interleukin‐1β protein in the neurohypophysis and provided further evidence for reduction in levels of IL‐1β immunoreactivity after stimulation of secretory activity. These results suggest an endogenous neuronal source of interleukin‐1β exists within the rat magnocellular neurosecretory system under normal physiological conditions. The potential for activity‐dependent release of IL‐1β and implications for the involvement of interleukin‐1β in regulation of neurosecretory activity are discussed. J. Neurosci. Res. 60:478–489, 2000 © 2000 Wiley‐Liss, Inc.