β‐Nerve Growth Factor Measurements in Mouse Serum

Abstract

Mouse serum .beta.-nerve growth factor (NGF) levels were measured using a newly developed competitive .beta.-NGF radioimmunoassay. The basal serum .beta.-NGF levels in male and female mice were consistently < 2 ng/ml when these animals were maintained in individual cages for at least 7 days before they were killed. However, in male mice, serum .beta.-NGF levels were significantly elevated when they were housed 5 per cage. The rise in serum .beta.-NGF levels, presumably mediated by intermale aggression, was confirmed by grouping previously isolated mice together in one cage for 20 min before they were killed. In all aggressive male mice, serum .beta.-NGF levels were elevated by two orders of magnitude. The .beta.-NGF radioimmunoassay values were also validated by a neurite outgrowth bioassay system using the serum of aggressive male mice. In summary, both measurement techniques confirm that mouse serum .beta.-NGF levels undergo marked changes depending on animal handling conditions.