Fig. 3.

Circumstantial evidence for axonal delivery of NT4 in corticocortical cocultures. (A) Conditioned medium from NT4-transfected cocultures fails to promote NPY in untransfected age-matched cocultures. This result argues against a diffusible action of the neurotrophin. (B) Transfection of NT4 (expression from 60 to 70 DIV) strongly up-regulated the NPY expression in the transfected explant of corticocortical OTC and also in the nontransfected explant (C). (D) Mean percentage with SEM of NPY neurons in the experimental conditions of A–C in comparison with untransfected visual corticocortical OTC (VC-VC control). White matter is oriented downward. (Scale bar: 300 μm.) **, P < 0.01.