Distribution of nerve growth factor in cat brains following topical application of solution or Minipellet

The distribution of nerve growth factor (NGF) was studied after topical application of NGF solution or NGF Minipellet into the caudate nucleus of cat brains. Each aliquot of NGF solution or a piece of NGF Minipellet contains 200 micrograms of mouse 2.5S beta-NGF. The concentrations of NGF in various areas of the brain were determined by enzyme-linked immunosolvent assay (ELISA). The tissue concentrations of NGF were very high at 6 h after injection of NGF solution (124.0 +/- 2.46 to 2144.0 +/- 16.03 ng g-1), but quickly decreased on day 1. The tissue concentrations of NGF were low at 6 h after implantation of NGF Minipellet, but were considerably increased on day 1 (11.22 +/- 3.36 to 72.04 +/- 20.45 ng g-1), and slowly decreased during the following 6 to 14 days. The present study demonstrates the temporal and spatial profiles of NGF distribution in the brain of middle-sized animals after topical application. Injection of NGF solution resulted in abrupt, but very transient, elevation of tissue NGF. Implantation of NGF Minipellet maintained the tissue NGF at biologically effective levels for 6 to 14 days.