Rapid depletion and restoration of striatal met-enkephalin after ketamine

The acute administration of ketamine depletes methionine-enkephaline levels in rat striatum, as measured by radioimmunoassay. The maximum decrease of about 25% was observed 30 minutes after 100 mg.kg^?1, i.p. injection of the drug, enkephalin levels returning to normal within 90 minutes. Neither higher doses nor a double administration of ketamine produced any further depletion. These results indicate that ketamine interacts with the enkephalinergic system and suggests the presence of a limited and rapidly releasable pool of methionine-enkephaline in the brain.     

Inhibition of cortisone action in mice by heparin.

A single dose of heparin applied in a depot-form (Freund's incomplete adjuvant or Ca-phosphate gel) inhibits the effects of intraperitoneally injected cortisone on the lymphoid organs (thymus and spleen), on the peritoneal and peripheral lymphoid cell count and serum gamma globulin level as well as on the liver glycogen deposition in mice. The same dose of heparin did not influence the action of hydrocortisone measured on the thymic and spleen involution and liver glycogen content. The route of cortisone administration seems to be critical, as heparin shows no or only minor effects when cortisone is applied subcutaneously; moreover, the action of cortisone per se is more marked by subcutaneous than by intraperitoneal administration. The results suggest the hypothesis that heparin inhibits cortisone-cortisol conversion and this inhibition is mediated by macrophages.