Pituitary-adrenocortical response following repeated adrenocorticotropin secretagogue administration in the rat

• Published in: Stress medicine 1992-10, Vol.8 (4), p.207-211
• Main Authors: Scaccianoce, Sergio, Cigliana, Giovanni, Nicolai, Raffaella, Navarra, Domitilla, Muscolo, Luisa A. A., Angelucci, Luciano
• Format: Article
• Language: English
• Subjects: Adrenocortical activity; AVP; Biological and medical sciences; corticosterone; CRH; Fundamental and applied biological sciences. Psychology; General aspects. Hormone interactions. Hormone actions on several organ systems. Adaptive reactions; rat; stress; Vertebrates: endocrinology
• ISSN: 0748-8386; 1099-1700
• DOI: 10.1002/smi.2460080402

In the adult male Wistar rat with a pharmacological block of endogenous CRF release, exogenous CRH (0.3 μg/kg iv), administered 15 or 30 min after a first equal dose, was unable to further stimulate adrenocortical activity above the level attained with the first peptide injection. This pituitary–adrenocortial refractoriness towards CRH was not evident when the second CRH injection was performed 60 min after the first. In the same experimental conditions, exogenous vasopressin (AVP) (0.3 μg/kg iv) did not produce any adrenocortical activation. However, AVP (0.3 μg/kg iv), injected 15 min after a first similar dose, induced a small increase in plasma corticosterone concentrations. CRH pretreatment was found to greatly potentiate the adrenocortical effect of AVP injected 15–105 min later. These results, while confirming the refractoriness of the pituitary to responce to CRH after a prior stimulation with the same secretagoue, indicate that the adrenocortical response to CRH is regained 60 min after the first stimulation. Moreover, CRH activates a mechanism that greatly potentiates the secretagogue effect of AVP for a considerable time.