We assessed the effects of cold and isolation stress on arginine vasopressin (AVP) mRNA in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. Vasopressin mRNA levels were determined by in situ hybridization histochemistry at the cellular level. In posterior magnocellular neurons of the PVN isolation stress for 7 or 14 days increased vasopressin mRNA levels 28 and 29%, respectively, compared to group-housed controls. No significant alterations in vasopressin gene expression were observed in the SON after 7 or 14 days of isolation stress. Scattered magnocellular AVP mRNA-expressing cells of the medial parvocellular PVN showed increases of 19 and 34% after 7 and 14 days of isolation, respectively. We also studied the effect of cold or combined cold and isolation stress on vasopressin gene expression in the PVN and SON. Cold stress for 3 h daily for 4 consecutive days increased AVP mRNA levels in the posterior magnocellular PVN by 15%. Cold-isolated animals showed an increase of 21%. No significant effect on AVP mRNA levels in the SON was observed. In contrast to the posterior magnocellular PVN, cold or cold-isolation stress increased AVP mRNA in magnocellular neurons of the medial parvocellular region of the PVN by 25 and 43%, respectively, relative to control rats. These results suggest that psychological and metabolic stress may be added to the list of stressors that activate the hypothalamo-neurohypophysial system.
We have examined the isolated postsynaptic density (PSD) Pertussis Toxin-Activated ADP-Ribosylation. Pertussis toxin-activated ADP-ribosylation of SM and PSD proteins was performed as described using [32P]NADP (35). The samples were processed by SDS/PAGE and autoradiography (36), with the polyacrylamide gel being a 7.5-15% linear gradient in all cases.
MATERIALS AND METHODS
Materials. Guanosine 5'-[-[35S]thio]triphosphate (GTP[-35S]) (1400Immunochemical Characterization of the G Proteins. To identify the G proteins in the SM and PSD fractions, the subcellular fractions (60 ,ug each) were subjected to SDS/ PAGE and the resolved proteins in the gel were transferred electrophoretically to Immobilon (Millipore) paper as described (37). The Western blot blots were probed with anti-Ga antibodies followed by 125I-labeled protein A (38).
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