Evidence for the existence of a corticotropin-releasing factor in the pigeon hypothalamus.

Abstract

Evidence is presented for the existence of a corticotropin-releasing factor in the pigeon hypothalamus employing an intrapituitary microinjection method. A crude acetic acid saline extract of pigeon median eminence was shown to increase significantly plasma corticosterone levels in the dexamethasone–chlorpromazine–Nembutal blocked assay rats. On the other hand, the crude extract of brain cortex of the bird failed to elevate plasma steroid levels in the assay animals. A dose–response relationship was obtained between the dose of the median eminence extract and plasma corticosterone increments. Arginine vasotocin, oxytocin, epinephrine, and norepinephrine were ineffective in eliciting adrenocorticotropic hormone (ACTH) release when injected directly into the adenohypophysis of the assay rats.It was concluded that the ACTH releasing effect of the hypothalamic extracts was not due to the neurohypophysial hormones or to catecholamines, but due to a corticotropin-releasing factor (CRF). These observations are discussed with special reference to the specificity of CRF activity.