Fig. 4.

Gene therapy strategies to decrease descending facilitation from the DRt and cVLM. Overexpression of depressed receptors (µ-opioid, δ-opioid and GABA_B receptors) in neurons of both pain control areas can be induced by lentiviral vectors containing transgenes for each receptor. A synaptically mediated increase in the release of opioids and GABA in the DRt can be achieved by HSV-1 constructs retrogradely transported (thin arrow) to the noradrenergic DRt afferents, using a TH promoter to control the expression of preproenkephalin or the GABA synthesizing enzyme GAD 67. The transgene product is then anterogradely released in the DRt (thick arrow).