Nowadays, the worldwide tendency regarding acupuncture research tries to find the physiological mechanisms that would be responsible of the effects observed with the stimulation of the acupoints.  In this sense, a fundamental breakthrough was given between 1977 and 1980 when it was discovered that the analgesic effects of acupuncture could be blocked if naloxone, an opioid antagonist, was administered. This means that the analgesic effects of acupuncture took place when the anti-nociceptive pathways were activated, mediated by the release of endorphines.  This neurologic pathways whose principal effectors are beta-encephalin and dinorphine, has been characterized up until being located in the gray periacueductal substance and the hipotalamus, which seem responsible for a central analgesic effect of acupuncture, one that is susceptible to being inhibited by naloxone.  However, other analgesic mechanisms of acupuncture, strictly local, seem to involve a certain level of sympathetic blockage and are not inhibited by naloxone.

In other research studies the afferent tracts and central analgesic action sites of electroacupuncture have been characterized, locating them in the enterolateral tract of the spinal cord, the reticulogigantocellular nucleous, the raphe magnus, the dorsal portion of the medial part of the periacueductal gray substance, the anterior and posterior hipotalamus and the medial part of the centro-medial nucleous of the thalamus.  More recent studies have demonstrated that electroacupuncture applied to acupoints in the calf (E36, Zuzanli) induce a greater neuronal expression of nitric oxide syntethase and NADPH diaphorase in the gracilis nucleous.  The nitric oxide mediates the acupunctural signals through the nervous pathways of the dorsal spine and the thalamus.

Other caracterizad effects include an inhibiting effect of acupuncture on the caudal nucleous of the trigeminal and the posterior shaft of the spinal cord, seemingly mediated by the supression of the local liberation of P substance which involves the modulation of serotonergic and opioid pathways. The caudal nucleous of the trigeminal (CNT) is the place of  neuronal interaction between nociceptive neurons of first and second order. The CNT receives the afferent signals of pain captured by the trigeminal nerve of the blood vessels and the dura.

The caudal nucleous of the trigeminal (CNT) throws its signal towards various brain rostral structures, including the rostral nucleous of the trigeminal, the nucleous of the solitary pathway, the reticular formation, the thalamus, hipothalamus, ipsilateral cerebellum, limbic system, cingular cortex, insular cortex and areas of audio/visual association. In exchange, recieves the central inhibitory modulation of many structures like the nucleous raphe magnus, nucleous of the dorsal raphe, the periacueductal gray area, ventromedial rostral nucleous, locus ceruleus, insular cortex, hipothalamus, somatosensorial cortex. There is enough evidence to affirm that the stimulation of some acupoints is capable of activating some of these structures that perform an inhibitory action on the CNT. For example, the aplication of electroacupuncture on the ID18 Quanliao increases the neuronal activity (measured by the expression of c-fos proteins) in the nucleous of the dorsal raphe, the locus ceruleus, the hipothalamus, the thalamus and the rostroventral marrow in rats, which inhibit the activity of the CNT and are responsable for the analgesic effect of acupuncture.

It is also known that the effects that modulate pain observed with acupuncture have a foundation in the spinal cord, activating the biosynthesis of pro-encefalin and therefore increasing the expression of beta-encefalin and dinorphine through the length of the anti-nociceptive descending pathways of the posterior pith of the spinal cord.  In addition, a larger expression of mu receptors (opioids) in the pheriacueductal gray area, the rostroventral nucleous, the hipothalamus and the amygdala.  Another descending pathway activated by acupuncture is the noradrenergic in the reticular gigantocellular nucleous, this inhibiting noradrenergic pathway being responsable of the rise on the  threshold of pain observed in acupunctural treatments.