Fig. 3
From: Excitatory and inhibitory neuronal signaling in inflammatory and diabetic neuropathic pain
Forward inhibition and allodynia. Nociceptive and non-nociceptive signals are summated in nociceptive projection neurons, providing a control gate (Wall 1978) defining the input of signals to the brain. Transmission of pain signals is modulated by inhibitory glycinergic and/or GABAergic interneurons. A Under normal conditions, simultaneous activation of pain (1) and touch (2) receptors does not lead to pain sensation. B In case of inactivation of inhibitory interneurons (disinhibition), even tactile stimuli alone (2) lead to sensation of pain