Chicken cerebrospinal fluid: normal composition and response to insulin administration.

1. With the exception of Na, K and Cl clear cerebrospinal fluid (c.s.f.) obtained from chickens varying in age from 6 weeks to 2 years did not reveal significant alterations in composition as could be related to age per se.2. Considerably higher levels of total protein and glucose are found in chicken c.s.f. than are found in mammalian fluid; slightly more chloride is found in chicken than most mammalian c.s.f.'s.3. Intravenous beef insulin depressed chicken cerebrospinal fluid glucose levels; insulin placed intracisternally had no effect on the avian glycogen body glycogen content indicating that c.s.f. glucose constancy, with or without glycogen body assistance, is not responsible for the resistance of the chicken to pharmacological doses of insulin.4. Bovine insulin injected into the cisterna magna of chickens depresses plasma glucose partially by acting over vagal pathways to release endogenous insulin and partially by diffusion across the c.s.f.-blood barrier to exert a peripheral effect.