Ageing and the Diurnal Expression of the mRNAs for Vasopressin and for the V1a and V1b Vasopressin Receptors in the Suprachiasmatic Nucleus of Male Rats

Jun 11, 2004Journal of neuroendocrinology

Age-related changes in daily patterns of vasopressin and its receptor gene activity in the brain's biological clock of male rats

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Abstract

The amplitude of the diurnal rhythm of V(1a) receptor mRNA expression is reduced in aged male rats compared to young adults.

Changes in neuropeptide synthesizing cells in the suprachiasmatic nucleus (SCN) may contribute to rhythm disturbances found in aging.
Both young adult and aged rats show a similar pattern and amplitude for the diurnal rhythm of AVP mRNA in the SCN.
A significant diurnal rhythm in V(1a) receptor mRNA expression is present in both age groups, but is less pronounced in aged rats.
In aged rats, V(1a) receptor mRNA shows increased levels during the light phase and early night.
V(1b) receptor mRNA does not exhibit a significant diurnal rhythm in either the SCN or supraoptic nucleus (SON), but elevated levels persist in aged rats at both sites.

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Changes in the function of neuropeptide synthesizing cells within the suprachiasmatic nucleus (SCN), the site of the predominant circadian pacemaker, may underlie the disturbance of rhythms observed during ageing. Arginine vasopressin (AVP) is synthesized by nearly one-third of SCN neurones in the rat. This peptide has predominantly excitatory actions within the SCN mediated by V(1)-type receptors; the extent to which the V(1a) and/or V(1b) receptor subtypes are involved in SCN functions remains to be determined. The present study used isotopic in situ hybridization histochemistry to examine the effects of ageing on expression of mRNAs for AVP and V(1a) in the SCN and for V(1b) in the SCN and supraoptic nucleus (SON) of male rats kept under a 12 : 12 h light/dark cycle. Analysis of film autoradiographs from young adult (2-3-month-old; n = 40) or aged (19-20-month-old; n = 40) animals, at eight time points across the light/dark cycle, revealed an equivalent pattern and amplitude for the diurnal rhythm of AVP mRNA in the SCN of the young adult and aged groups. Both groups also displayed a significant diurnal rhythm in the expression of V(1a) receptor mRNA; however, the amplitude of this rhythm was reduced in the aged group, due to increased levels during the light phase and early part of night. Although the expression of V(1b) mRNA did not display a significant diurnal rhythm within the SCN or SON, persistently elevated levels for V(1b) mRNA were observed in the aged group at both sites.

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Ageing and the Diurnal Expression of the mRNAs for Vasopressin and for the V1a and V1b Vasopressin Receptors in the Suprachiasmatic Nucleus of Male Rats

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