Plasma and cerebrospinal fluid α-MSH levels in the rat after hypophysectomy and stimulation of pituitary α-MSH secretion

Abstract

This lack of correlation between a-MSH levels in the CSF and plasma suggests that the systemic circulation does not deliver u-MSH to the CSF. The apparently normal levels of u-MSH in the hypothalamus after hypophysectomy suggests that this tissue is able to synthesize u-MSH and it is possible that the hypothalamus is a source of the a-MSH in the CSF.Cerebrospinal fluid a-MSH ~ER~~R~~~IN~ FLXJED fCSF3 is likely to serve as an important route for many hormones that modulate bmin function. A number of deferent peptide hormones have been found in the CSF [l, 3, 5-7, 9, 12, 241 and while those of hy~~thal~ic origin such as vasopressin, oxytocin and the releasing hormones enter the CSF directly, the way in which pituitary hormones such as ACTS reach the CSF is not yet clear.weight. ~y~~hy~ctorny was performed by the pam~h~~ge~ approach and con&met3 at autopsy by examination of the seUa turcia.Melanocyte-stimulating hormone (MSH) and related peptides are known to affect brain function both in man and ex~e~me~tal animals 12, 11, 28, 291. While it is generally accepted that these melanotropic peptides are produced by the pituitary gland bioassayable MSH and immunoreactive MSH peptides have been found in different regions of the brain and shown to persist after removal of the pituitary [S, 14, 1.5, 17, 18,2%23]. This suggests that the brain, as weif as the pituitary, is capable of producing MSH peptides. fn this study we report the presence of ~mmunnrea~tive cu-MSH in the CSF of the rat and present data which suggest that at teast some of this peptide is of brain rather t.han pituitary origin.Rats were anaesthetized with urethane (1.1 g/Kg IP) and polyethylene cannulae inserted into the cistema magna for the withdrawal of CSF [7]. Approximately SO-100 1,t1 CSF were wi~d~aw~~ centrifuged and stored at -20°C until assayed.(1) Polyethylene cannulae were inserted into the jugular vein and advanced to the heart. Approximately 500 ~1 blood were withdrawn and replaced by an equal votume of 0.5% salineiheparin solution.(2) In experiment 2 {see below) the rats were decapitated and trunk blood collected into tubes containing lithium sequestrene,.All blood samples were centrifuged and the plasma stored at -20°C. METHODMale Wistar rats were obtained from TNO, Zeist, The Rats were decapitated and the brain immediately reNetherlands or bred in the Depa~ment of Dermatology, moved. The hypothalamus was dissected and this and the Newcastle, and were used when approximately 180 g in remainder of the brain minus the olfactory lobes were rinsed

Characterization of the α-MSH-like immunoreactivity in blood and cerebrospinal fluid of the rat

“…The origin of -MSH-LI in CSF has not yet been established but a CNS origin seems the most obvious. It is unlikely that CSF a-MSH-LI originates either from peripheral blood or from the pituitary since a transport from blood to CSF occurrs only in very small quantities (De Rotte et al 1982) and a pituitary origin of CSF -MSH-LI seemed less likely after it was demon¬ strated that rats have normal or sometimes even elevated CSF -MSH-LI levels after hypophysectomy (Thody et al 1979). …”

Immunoreactive ACTH in the cerebrospinal fluid of the rat: decrease after mediobasal hypothalamic lesion and hypophysectomy, increase after adrenalectomy

“…On the other hand, POMC-containing cell bodies have been identified immunocytochemically in the arcuate nucleus of the hypothalamus and in the nucleus tractus solitarius (15,16). Data suggest that POMC-derived peptides in the CSF and in the plasma form two separate pools representing various sources under different regulation (9,(18)(19)(20); further¬ more, that ßE and a-MSH in the CSF are of central origin and their concentrations reflect brain activity (9,(21)(22)(23)(24)(25). Data suggest that POMC-derived peptides in the CSF and in the plasma form two separate pools representing various sources under different regulation (9,(18)(19)(20); further¬ more, that ßE and a-MSH in the CSF are of central origin and their concentrations reflect brain activity (9,(21)(22)(23)(24)(25).…”