Retrograde axonal transportation and NGF-dependent sensory neurons with diminished expression of neuropeptides substance P and calcitonin gene-related peptide (SP, CGRP) are affected by the absence of TRKA (tropomyosin receptor kinase A) in hyperglycemia (Tomlinson, Fernyhough, and Diemel 1997). The gene discussed is NTRK1; the disease is Hyperglycemia.