Exenatide-induced phosphorylation of p38 and CREB was also totally blocked by the PKA inhibitor and siRNA/p38<i>β</i>, but not by siRNA/p38<i>α</i> Seven-day intrathecal injections of siRNA/p38<i>β</i> (but not siRNA/p38<i>α</i>) completely blocked exenatide-induced spinal p38 activation, <i>β</i>-endorphin expression, and mechanical antiallodynia in rats with established neuropathy, although siRNA/p38<i>β</i> and siRNA/p38<i>α</i> were not antiallodynic.