Proceedings of The Physiological Society

University of Bristol (2005) J Physiol 567P, PC61

Poster Communications

The transcription factor JunD is up-regulated in the endocrine hypothalamus at both the mRNA and protein level in water-deprived rats

Yao, Song; Gouraud, Sabine; Paton, Julian F.R.; Murphy, David;

1. Henry Wellcome LINE, University of Bristol, Bristol, AVON, United Kingdom. 2. Department of Physiology, University of Bristol, Bristol, AVON, United Kingdom.

In an attempt to understand the molecular basis of hypothalamic regulation of blood volume homeostasis we are interested in the regulation of transcription factors. JunD is a member of the family of activator protein-1 (AP-1) transcription factors. While past studies have demonstrated a change in the expression of transcription factors such as c-Fos in the paraventricular (PVN) and supraoptic nucleus (SON) (Morien et al. 1999), no study to date has examine changes in the expression of JunD in response to water deprivation, despite its reported presence within the rat hypothalamus (Herdegen et al. 1995). For immunohistochemistry, male Sprague-Dawley rats (200-300g, n=12) were randomly assigned to two groups, a control and a 72-hour water-deprived group. Following water deprivation, rats were deeply anaesthetised with pentobarbitone sodium (100mg/kg i.p.), transcardially perfused with phosphate buffered saline and 4% paraformaldehyde and the brains processed for immunohistochemical detection of JunD. For mRNA quantification (n=4), the SON was excised from fresh hypothalamic slices and the total RNA was extracted and quantified using real-time PCR. Control, euhydrated rats exhibited very little expression of JunD-like immunoreactivity, where only very few cells within the SON (34±11) and PVN (22±7) showed any staining. In contrast, there was a significant (P<0.05, unpaired t test) increase in the number of JunD-like immunoreactive cells (SON, 128±13; PVN, 116±24) in the water-deprived rats. Moreover, quantitative RT-PCR revealed a significant increase (fold change 1.58±0.27) of JunD mRNA expression in the SON after 3 days of dehydration (P<0.05). This study provides the first demonstration of the up-regulation of JunD mRNA within the SON and changes at the protein level in both the SON and PVN following water deprivation. These results suggest a role for JunD in the regulation of magnocellular neurones for body fluid homeostasis.

Where applicable, experiments conform with Society ethical requirements