Effect of Intrathecal Injection of Melanotropic-Lipolytic Peptides on the Concentration of 3′,5′ Cyclic Adenosine Monophosphate in Cerebrospinal Fluid

Abstract

Rabbits were anesthetized with urethane, and the concentration of 3′,5′ cyclic adenosine monophosphate (cAMP) in cerebrospinal fluid (CSF) was measured before and after injection into the cisterna magna of the following biologically active peptides and amines: adrenocorticotropin (ACTH), β-melanocyte-stimulating hormone (β-MSH), choroid plexus peptide IIF, arginine vasopressin, oxytocin, glucagon, epinephrine, serotonin, histamine, and acetylcholine. Only epinephrine and the lipolytic-melanotropic peptides ACTH, β-MSH, and IIF influenced cAMP. Five to 500 μg ACTH caused a 3 to 10× increase in cAMP within 30 min; the concentration of nucleotide returned to baseline within 60–90 min after 5 or 50 μg, and remained elevated for at least 120 min after 500 μg. Effects of the same magnitude and tempo as those caused by 5 to 500 μg ACTH were produced by .1 to 10 μg β-MSH and 5 to 500 μg IIF. Epinephrine at doses of 5 to 500 μg caused rises in cAMP of similar degree as the same dose of ACTH or peptide IIF, but the peak value was not reached until 60 to 90 min after injection. (Endocrinology97: 1476, 1975)