Pain is a response of the body to the action of injuring stimuli. Notwithstanding an unpleasant experience, it appears to be an important component of the defence system of the organism and a permanent regulator of homeostatic reaction. The organism's reaction to pain is a multi-component one and involves sensory-discriminative, emotional-affective and cognitive characteristics. Clinically, neuropathic pain is characterised by spontaneous ongoing or shooting pain and evoked amplified pain responses after nocuous or innocuous stimuli. The study of pain, therefore, and search for the treatment strategies has a paramount role in modern neurobiology. Numerous anatomy-physiological studies have revealed a number of brain structures involved in the shaping of pain and endogenous analgesia. This book presents and examines current research discovered in a behavioural study of 'non-opioid' tolerance.