Tölle, T. R., Herdegen, T., Schadrack, J., Bravo, R., Zimmermann, M., & Zieglgänsberger, W. (1994). Application of morphine prior to noxious stimulation differentially modulates expression of FOS, JUN and KROX-24 proteins in rat spinal cord neurons. Neuroscience, 58, 305-321.