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'' c[cyclic]AMP in CSF was measured before and after injection into the cisterna magna of the following biologically active peptides and amines: ACTH, .beta.-melanocyte-stimulating hormone (.beta.-MSH), choroid plexus peptide IIF, arginine vasopressin, oxytocin, glucagon, epinephrine, serotonin, histamine and acetylcholine. Only epinephrine and the lipolytic-melanotropic peptides ACTH, .beta.-MSH, and IIF influenced cAMP. Five to 500 .mu.g ACTH caused a 3-10.times. increase in cAMP within 30 min; the concentration of nucleotide returned to baseline within 60-90 min after 5 or 50 .mu.g, and remained elevated for at least 120 min after 500 .mu.g. Effects of the same magnitude and tempo as those caused by 5-500 .mu.g ACTH were produced by .1-10 .mu.g .beta.-MSH and 5-500 .mu.g IIF. Epinephrine at doses of 5-500 .mu.g caused rises in cAMP of similar degree as the same dose of ACTH or peptide IIF, but the peak value was not reached until 60-90 min after injection.