Age‐related modifications of the morphological organization of pituicytes are associated with alteration of the GABAergic and dopaminergic innervation afferent to the neurohypophysial lobe

Abstract

Ageing is known to induce a marked activation of astrocytes within various regions of the central nervous system. To date, the age-related factors responsible for these modifications are unknown. The neural lobe of the hypophysis (NL) is a particular brain region which does not contain neurons but does contain specialized astrocytes, called pituicytes, and numerous terminals of afferent axons, including (i) peptidergic neurohypophysial axons which terminate on the NL blood vessels, and (ii) axons containing both gamma amino-butyric acid (GABA) and dopamine (DA) which form contacts with pituicytes. Because evidence has recently been provided that GABA signalling mediates the morphological organization of astrocytes, the present study was designed to determine whether modifications of pituicytes during ageing were associated with modifications of the GABAergic axons innervating the NL. We show here that, in adult rats, GABA/DA axons form preferential synaptic-like contacts with pituicytes which express both GABAA and D2 dopamine receptors. We then show that, during ageing, pituicytes undergo dramatic modifications of their morphology, correlatively with marked modifications of the GABA/DA fibres innervating the NL. Lastly, in vitro experiments indicate that modifications of the morphology of pituicytes similar to those observed during ageing were obtained by incubating isolated NL of adult rats with a GABAA receptor agonist and/or a D2 dopamine receptor antagonist, whereas inverse modifications were observed when NL of aged rats were incubated with a GABAA receptor antagonist and a D2 dopamine receptor agonist. Taken together, these data suggest that the age-related morphological changes of pituicytes result from the alteration of the GABA/DAergic innervation of the NL.

Mechanisms Involved in Dual Vasopressin/Apelin Neuron Dysfunction during Aging

“…GFAP protein levels increase during aging, reflecting a sustained upregulation of astrocyte activity. These findings are consistent with published data for areas of the rodent brain [58], [59], [60], [61], [62], and they indicate that GFAP overexpression by astrocytes is a common feature of the aging process. In aged rats, vimentin- and GFAP-IR processes are retracted at the base of the SON, mostly in the VGL, whereas they spread throughout the SON in adult rats.…”

Age-Related Changes in Nestin Immunoreactivity in the Rat Pituitary Gland

“…As it ages, the pituitary gland undergoes transcriptional changes [43, 44], histological changes [17,45,46,47], tumorigenesis [19,20,21] and hyperplasia [48, 49]. This study reports for the first time that nestin is increased in the aging pituitary gland.…”

“…The pituitary gland is a very plastic organ that undergoes important cellular remodeling during development, physiological challenges and aging, consequently leading to hormonal output changes [14,15,16,17]. The pituitary gland is also very prone to tumorigenesis, since up to 25% of unselected human pituitary autopsies present benign adenomas [18] and up to 70% of rodents develop pituitary tumors as they age [19,20,21].…”

Revealing the large-scale network organization of growth hormone-secreting cells

“…The emitted fluorescence was recorded at 520 nm (8,9). In some experiments, high-pressure cardiac perfusion was performed before tissue fixation peroxidase immunostaining and electron microscopy as described (10). performed two complementary statistical tests.…”