Many studies reported suggest both neuronal precursor cells before innervation of target fields and the neurons of adult animal coexpress neurotrophic factors and their receptors, implying that autocrine and paracrine modes of NTFs exit.

• 研究表明，无论是靶组织联系建立以前的神经元前体细胞，还是成年后的神经元，均有神经营养因子与其受体的共同表达，提示有神经营养因子自分泌和旁分泌存在的可能性。