Different cholinergic pathways are involved in the improvement induced by CCK-8 and by ACTH-(1-24) in massive acute hemorrhage, in rats.

Cholecystokinin octapeptide (CCK-8) (20 micrograms/kg i.v.) and tetracosactide [ACTH-(1-24)] (160 micrograms/kg i.v.) restore blood pressure and allow rats subjected to otherwise invariably fatal acute hemorrhage to survive. Atropine sulphate (2-8 mg/kg i.p.), which crosses the blood-brain barrier, dose-dependently prevents this effect both in the case of ACTH-(1-24) and in that of CCK-8. On the other hand, atropine methyl bromide (2-8 mg/kg i.p.), which does not cross the blood-brain barrier, prevents the effect in the case of CCK-8, but not in that of ACTH-(1-24). These data suggest that a cholinergic mechanism is involved in the anti-shock effect of both ACTH-(1-24) and CCK-8, though the sites of action appear to be in the CNS, in the case of ACTH-(1-24), and outside the CNS, in that of CCK-8.