Changes of nNOS expression in the tuberal hypothalamic nuclei during ageing.

The hypothalamus is the most important integrator of autonomic and endocrine regulation in the body and it also has a fundamental role in ageing development and lifespan control. In order to better understand the role of NO-ergic system in the hypothalamic regulation of ageing, the purpose of this study was to investigate the expression of neuronal nitric oxide synthase (nNOS) in the arcuate (ARC), ventromedial (VMH) and dorsomedial (DMH) hypothalamic nuclei in young (2-3-month-old) and old (24-month-old) male and female rats using immunohistochemistry and western blot analysis. In young animals, only single nNOS-immunoreactive (IR) neurons were detected in ARC, and nNOS-IR neurons were found in the VMH (19 ± 3.2% in females and 14.5 ± 2.6% in males) and DMH (17 ± 4.0% in females and 21 ± 2.8% in males). In aged animals, the number of nNOS-IR neurons increased in all studied nuclei, including ARC (36 ± 3.1% in females and 33.5 ± 3.7% in males), VMH (83 ± 4.3% in females and 58 ± 2.1% in males) and DMH (57 ± 1.9% in females and 54 ± 1.8% in males). The expression of nNOS also significantly increased in the ARC, VMH and DMH during ageing by western blot analysis. In conclusion, ageing is accompanied by increasing of nNOS expression in the hypothalamus and this process is related to regions involved in the control of feeding behavior.

Changes of discharge properties of neurons from dorsomedial hypothalamic nuclei during aging in rats.

The hypothalamus is a vital brain center that is participated in the integration of the endocrine and nervous systems and control of the homeostasis and aging. Spontaneous firing activity from single neurons of the dorsomedial hypothalamic nucleus (DMN) was studied extracellularly in vivo in urethane-anaesthetized rats. The discharge patterns of the majority of DMN neurons were irregular, including periods of relatively stable activity interrupted by pauses. Based on the features of interval interspike histogram, we have selected neurons with an irregular arrhythmic activity (50% in young, 46% in adult and 44% in aged rats), with a constant rhythmic activity (18% of neurons in young, 19% in adult and 23% in aged rats), with a wide interspike interval distribution (22% in young, 26% in adult and 25% in aged rats) and cells with bursts of two or three spikes (10% in young, 9% in adult and 8% in aged rats). The firing rate of DMN neurons was 2.5 ± 0.12 Hz in young and 2.4 ± 0.21 Hz in adult rats and significantly decreased to 1.8 ± 0.17 Hz in aged rats.

Expression of calbindin and calretinin in the dorsomedial and ventromedial hypothalamic nuclei during aging.

The hypothalamus is involved in the regulation of rhythms, autonomic, endocrine, and behavioral functions and may also participate in aging development and control. The aim of this work was to study the expression of calbindin (CB) and calretinin (CR) in the ventromedial (VMH) and dorsomedial (DMH) hypothalamic nuclei in young and old rats of both sexes by immunohistochemistry and western blotting. In young animals, the largest number of CB-immunoreactive (IR) neurons was detected in the ventral part of DMH (DMHv) and smaller percentage was found in its dorsal part (DMHd), in the dorsomedial part of the VMH (VMHdm) and in the ventrolateral part of the VMH (VMHvl). In aged animals, the percentage of CB-IR neurons significantly decreased in all studied nuclei, including DMHv, DMHd, VMHdm and VMHvl. CR-IR neurons were found in moderate number in the DMHv, DMHd, VMHdm and VMHvl of young rats. In aged rats, the percentage of CR-IR neurons significantly increased in the DMHv, DMHd, VMHdm and VMHvl. Less than one third of IR neurons colocalized CB and CR in young and aged rats. The expression of CB significantly decreased, and the expression of CR significantly increased in the DMH and VMH during aging by western blot analysis. Thus, there are opposite changes of the calcium-binding proteins expression in the hypothalamic nuclei involved in the metabolic and sexual regulation during aging.