INSITU HYBRIDIZATION OF ARGININE-VASOPRESSIN (AVP) HETERONUCLEAR RIBONUCLEIC-ACID REVEALS INCREASED AVP GENE-TRANSCRIPTION IN THE RAT HYPOTHALAMIC PARAVENTRICULAR NUCLEUS IN RESPONSE TO EMOTIONAL-STRESS

The regulation of anterior pituitary adrenocorticotropin hormone (ACTH ) secretion during stress involves several hypothalamic neurohormones, including arginine vasopressin (AVP). In situ hybridization technique s have been used to study the regulation of neuropeptide messenger rib onucleic acids in the hypothalamus. Owing to the relatively slow time course of the changes in cytoplasmic messenger ribonucleic acid concen trations, rapid alterations in the level of neuropeptide gene transcri ption could not be detected. Because of its rapid processing, the nucl ear level of the heteronuclear ribonucleic acid should reflect the rat e of its synthesis, namely the transcription of the gene. We have used in situ hybridization with a probe complementary to a portion of an i ntronic sequence of the rat AVP gene to study rapid changes in the lev el of AVP gene transcription during emotional stress. The specificity of our technique was demonstrated by the localization of the hybridiza tion signals in the paraventricular nucleus, the supraoptic nucleus an d the suprachiasmatic nucleus, and was confirmed by the nuclear locali zation of the labeling. Isolation and exposure of male rats to a novel environment induced an activation of the pituitary-adrenal axis and a n increase in AVP heteronuclear ribonucleic acid concentrations in the paraventricular nucleus 2 h after the onset of the stress, suggesting that an increased AVP gene transcription may play a role in the activ ation of the pituitary-adrenal axis in response to emotional stress.