Immune challenge-stimulated hypophysiotropic corticotropin-releasing hormone messenger RNA expression is associated with an induction of neurotensin messenger RNAs without alteration of vasopressin messenger RNAs.
The corticotropin-releasing hormone neurons of the hypothalamic paraventricular nucleus are the final common pathway of the neuroendocrine adaptative response to a variety of stressors. To meet varied homeostatic needs, corticotropin-releasing hormone neurons exhibit a marked phenotypical plasticity, enabling them to rapidly modify their neuroendocrine output. In particular, they synthesize the neuropeptides vasopressin and neurotensin. Under many experimental circumstances, it is observed that corticotropin-releasing hormone and vasopressin are regulated in parallel, whereas the expression of neurotensin seems dissociated, in these neurons, evoking different transcriptional control over the co-existing neuropeptides depending on the adaptative response required. Using radioactive and dual-label in situ hybridization techniques, we have studied the respective expression of paraventricular corticotropin-releasing hormone, vasopressin and neurotensin messenger RNAs in the context of an immune challenge. A single intraperitoneal injection of the endotoxin lipopolysaccharide was administered to adult male rats that were killed 8 h later. Compared to control animals, lipopolysaccharide-injected rats showed elevated plasma corticosterone (614+/-65 vs 185+/-40 ng/ml in control) and increased expression of paraventricular corticotropin-releasing hormone messenger RNA (+200%); expression of neurotensin messenger RNA was induced in about one-third of corticotropin-releasing hormone neurons, whereas vasopressin messenger RNA expression remained unchanged. Therefore, in this experimental context and at the time-point examined, co-existing corticotropin-releasing hormone and vasopressin appeared differentially expressed, and an additional stimulus (inflammation) is demonstrated to result in neurotensin expression in neuroendocrine corticotropin-releasing hormone neurons. Neurotensin may be released in the pituitary portal blood to trigger pituitary response associated with mobilization of the immune system.
Juaneda
C
C
Laboratoire de Neurocytochimie Fonctionnelle, Université de Bordeaux I, CNRS-UMR 5807, Talence, France.
Lafon-Dubourg
P
P
Ciofi
P
P
Sarrieau
A
A
Corio
M
M
Tramu
G
G
D000818:Animals; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis*; D004731:Endotoxins / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D007109:Immunity / Q000502:physiology*; D017403:In Situ Hybridization; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009496:Neurotensin / Q000096:biosynthesis*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D014667:Vasopressins / Q000096:biosynthesis*
D004731:Endotoxins; D008070:Lipopolysaccharides; D015347:RNA Probes; D012333:RNA, Messenger; D014667:Vasopressins; D009496:Neurotensin; C044101:endotoxin, Escherichia coli; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone