Rapid changes in heteronuclear RNA for corticotrophin-releasing hormone and arginine vasopressin in response to acute stress

The rapid detection of gene activation is important for our understanding of gene regulation. We have therefore studied heteronuclear (i.e. nascent) RNA (hnRNA) by using S-35-labelled corticotrophin-releasing hormone (CRH) riboprobes and arginine vasopressin (AVP) oligonucleotide probes directed against intronic and exonic sequences of both CRH and AVP transcripts for in situ hybridization studies of transcriptional changes during acute stress. CRH and AVP intronic signals (found in newly synthesized transcripts) were confined to the nuclei of the parvocellular cells in the paraventricular nucleus (PVN) whilst CRH and AVP exonic signals (found in both newly formed and mature transcripts) were primarily located in the cytoplasm of these cells. AVP hnRNA and mRNA were also present at high levels in the magnocellular PVN. The levels of CRH hnRNA and parvocellular AVP hnRNA in the PVN were significantly increased 1 and 2 h after the onset of restraint. The levels of CRH mRNA on the other hand were not significantly increased until 4 h after the onset of restraint. The number of AVP mRNA-expressing neurons in the medial parvocellular cells of the PVN significantly increased at 2 h and peaked at 4 h after the onset of stress. In contrast, densitometric analysis indicated that the increase in AVP mRNA levels in these cells did not reach significant difference from control until 4 h after the onset of restraint. There were no significant changes in AW hnRNA or AVP mRNA levels in the magnocellular subdivision of PVN at any time point after the onset of restraint.