Activity of Vasopressinergic Neurones of the Human Supraoptic Nucleus os Age‐ and Sex‐Dependent

Abstract

In the human hypothalamus, arginine-vasopressin (AVP) is produced for a major part by the neurones of the supraoptic nucleus (SON). Since plasma AVP levels in men were reported to be higher than those of women and we did not find a sex difference in the neurone number, a higher vasopressinergic neurone activity was supposed to be present in the SON of men. Therefore we studied the size of the Golgi-apparatus (GA), which has been demonstrated previously to be a sensitive parameter for protein synthetic ability of neurones, in 15 men and 17 women ranging in age from 29 to 94 years. A polyclonal antibody against immunoaffinity purified MG-160, a sialoglycoprotein of the medial cisternae of the GA was applied on paraffin-embedded sections containing the dorsolateral SON (dl-SON) from which 90-95% of neurones are vasopressinergic. SON areas that contain oxytocin (OT) cells were excluded on the basis of adjacent sections stained with a monoclonal antibody against OT. By means of an image analysis system the size of the GA and the cellular profile area were determined in dl-SON neurones with a nucleolus. Our results showed indeed an age-dependent sex difference in the size of the GA that appeared to be twice as large in young men (< or = 50 years old) than in young women of the same age. The size of the GA increased with age in women but not in men. In addition, the mean cell profile area, another measure for neuronal activity, was significantly larger in young men than in young women and was in old women larger than in young women. In conclusion, these data show the presence of a sex-dependent age-difference in the activity of vasopressinergic neurones in dl-SON which may relate to differences in AVP and sex hormone levels and kidney AVP receptors.

Developmental changes of nitric oxide synthase expression in the rat hypothalamoneurohypophyseal system

“…There are various measures of neuronal activity. The most sensitive of these seems to be cell size (Fliers et al, 1985;Ishunina et al, 1999). In our present study, we found that the increase of nNOS immunoreactivity in the SON and PVN is accompanied by an increase in cell size of AVP and OT neurons with age.…”

“…The SON is a well-delineated structure and consists almost exclusively of magnocellular elements projecting to the neurohypophysis (Swanson and Sawchenko, 1983;Armstrong, 1995), whereas the PVN is intermingled with nonneurosecretory parvocellular cell bodies that project elsewhere (Swaab et al, 1975). The nonneurosecretory parvocellular cells that project to the spinal cord or brainstem have different functions from that of magnocellular cells projecting to neurohypophysis (Ishunina et al, 1999;Nylen et al, 2001). Thus, it is possible that they do not mature at the same time.…”

Estrogen effects on osmotic regulation of AVP and fluid balance

“…AVP is synthesized in the cell bodies of the paraventricular (PVN) and supraoptic (SON) nuclei, located in the anterior hypothalamus. Axons from these areas project into the posterior pituitary, where AVP is stored and released in response to stimulation of central osmoreceptors.Estrogen receptors are present in the PVN and SON of both animals (17, 33) and humans (19), and a number of studies have demonstrated sex differences in AVP neuron size in these nuclei (20,21).Resting plasma AVP levels are greater in males than in females (34, 37), and men have greater AVP sensitivity and blood pressure responses to hypertonic saline infusion (41). On the other hand, in postmenopausal women, estrogen administration increases resting plasma AVP and shifts the osmotic threshold for AVP release to a lower plasma osmolality (36).…”

“…Estrogen receptors are present in the PVN and SON of both animals (17,33) and humans (19), and a number of studies have demonstrated sex differences in AVP neuron size in these nuclei (20,21).…”

Sexual Differentiation of Physiological Functions

“…Moreover, a functional sex difference was found recently that is not reflected in differences in neuronal numbers, but only in neuronal activity. In the supraoptic nucleus, the vasopressin neurons are more active in males than in females, explaining the sex difference in plasma vasopressin levels (Ishunina et al 1999). In addition, structural dimorphism related to sexual orientation (i.e.…”