Rapid pulsatile corticosterone response in unanesthetized individual rats.

Plasma corticosterone concentrations were determined by radioimmunoassay of blood samples obtained rapidly and repeatedly from individual unanesthetized rats at time intervals of approximately 10 seconds. Results confirm that corticosterone release is pulsatile, as has been reported previously, but with a much faster time course and a pulse frequency close to one pulse per minute. Such a release pattern is consistent with and required by the theory that there are rate sensitive hormone receptors. Failure of others to observe such a rapid response is presumably attributable to their use of much longer intervals between samples or of sampling procedures and techniques that obliterate any variation from a preconceived smooth function.