Regulation of spinal nociceptive processing: where we went when we wandered onto the path marked by the gate

The formalization that represented the Gate Control Hypothesis possessed two defining characteristics. Firstly, it served to integrate the body of literature which suggested that processing of nociceptive information is subject to a dynamic regulation, thereby providing a theoretical framework for processes leading to hyper- as well as hypo-algesia. Secondly, the localization of this gating mechanism was placed decisively in the spinal dorsal horn. Subsequent work reflecting upon the pharmacology of spinal systems has served to emphasize the importance of this spinal regulatory process. The complexity of these spinal systems has led to significant advances in our understanding of the transmitter systems by which these gating systems function. It has had the practical consequence of providing important therapeutic modalities serving to control pain processing which originates from both tissue and nerve injury by drugs which are limited in their distribution to the spinal cord.