Ageing and the Diurnal Expression of the mRNAs for Vasopressin and for the V_1a and V_1b Vasopressin Receptors in the Suprachiasmatic Nucleus of Male Rats

Abstract

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.

Vasopressin: Behavioral roles of an “original” neuropeptide

“…In two mice lines selected for nest-building behavior, differences in circadian rhythms are accompanied by different number of Avp-ir neurons in the SCN, as well as different transport and release of Avp in the SCN ( Van der Veen et al, 2005). Reduced diurnal rhythms of Avpr1a mRNA in the SCN are seen in aged (19-20 months old), compared to young, rats (2-3 months old) (Kalamatianos et al, 2004). Evidence in golden hamsters, Mesocricetus auratus, indicates that lesions to the SCN reduce the number of Avp-ir fibers throughout the brain, but seem to affect only circadian locomotor behavior (wheel running), and not another Avp-dependent behavior, flank marking (see section 2.2.1) (Delville et al, 1998).…”

Aging of the Mammalian Circadian Timing System: Changes in the Central Pacemaker and Its Regulation by Photic and Nonphotic Signals

“…C lock and Bmal1 ) [168] , and neuropeptide gene expression (e.g. VIP) [171][172][173] . With the exception of the latter, these studies have considered the SCN as a homogeneous unit.…”

“…Thus, the aging circadian pacemaker exhibits some plasticity. Also, aging may induce compensatory changes, such as increased expression of mRNAs for the V1a and V1b vasopressin receptors in the rat SCN [173] .…”

“…In male and female rats and male hamsters ( fig. 3 ), aging decreases SCN expression of VIP mRNA but not vasopressin mRNA [171][172][173] . The selectivity of the effect of aging on VIP mRNA expression is also emphasized by findings that SCN mRNA expression of somatostatin, typically located in the dorsal SCN, or GAD67, an enzyme required for the synthesis of the neurotransmitter GABA that is broadly distributed throughout the SCN, are also apparently unaffected by aging [172,174] .…”

Peculiarities of Modulation by Arginine-vasopressin the Regular and Non-Regular Spike Activity of the Suprahiasmtic Nucleus Neurons

“…Нейропептидом, наиболее широко распростра-нённым в супрахиазматическом ядре, является аргинин-вазопрессин, который продуцируется примерно третью расположенных здесь клеток. Кроме того, в данном ядре выявлена высокая доля нейронов (более 40%), осуществляющих процессинг специфических для этого пептида рецепторов V1a [1,2]. Эти данные косвенно ука-зывают на важность роли вазопрессинергических структур в функции циркадианного осциллятора супрахиазматического ядра, однако механизмы физиологической активности аргинин-вазопрес-сина на уровне данного гипоталамического ядра изучены недостаточно.…”