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

Immunoreactive alpha-MSH was measured in cerebrospinal fluid (CSF) and plasma of rats. While treatment with haloperidol increased alpha-MSH levels in the plasma concentration of alpha-MSH in the CSF showed little change. Hypophysectomy also had little effect on the concentration of alpha-MSH in the CSF despite the fall in plasma alpha-MSH levels. This lack of correlation between alpha-MSH levels in the CSF and plasma suggests that the systemic circulation does not deliver alpha-MSH to the CSF. The apparently normal levels of alpha-MSH in the hypothalamus after hypophysectomy suggests that this tissue is able to synthesize alpha-MSH and it is possible that the hypothalamus is a source of the alpha-MSH in the CSF.