Increased Nerve Growth Factor Signaling in Sensory Neurons of Early Diabetic Rats Is Corrected by Electroacupuncture
Figure 7
Schematic representation of NGF system activation following STZ and EA in the sensory circuitry linking a peripheral organ (the skin), the sensory neurons located in DRG and their central innervation structure (the spinal cord). The represented mechanism is drawn on the basis of experimental results shown in the present and our previous [3] papers. The DRG neurons receive NGF as a trophic support from both innervation fields. NGF increases throughout the entire circuitry in the first 4 weeks after STZ injection. This NGF increased availability corresponds to the NGF overactivity mediated by TrkA receptor in the spinal cord and by in the skin. As a result, both NGF and NGF receptors are overexpressed in the DRG neurons, with a prevalent activation of NGF receptor signaling known to be apoptosis-related and by enhanced presence and possibly activity of the NGF-regulated ion channel TRPV1, known to trigger hyperalgesia as well as neuronal sufferance (see Section 4). Electroacupuncture regulates the activity-dependent NGF synthesis and functions, restores basal nociception and decreases NGF content in the spinal cord and DRG, normalizes TrkA activation in the spinal cord as well as presence in the skin and counteracts the STZ-induced events, triggered by JNK/p38 and TRPV1 (possibly a commitment of sensory neurons to apoptosis and neuronal sufferance due to calcium overload, resp.).
