A study of the catecholaminergic systems of the lateral reticular nuclei and the serotoninergic systems of the raphe magnus in various types of analgesia

Abstract

The effects of catecholaminergic A-1 lateral reticular nuclei and serotoninergic neurons of NRM [of the rat] on pain reactions before and after various types of stimulation are presented. Specific lesions of catecholaminergic (NE) neurons in A-1 nuclei using 6-hydroxydopamine, and of serotoninergic (5-HT) [5-hydroxytryptamine] neurons of the nucleus raphe magnus using 5,7-dihydroxytryptamine caused a decrease in the respective levels of epinephrine and serotonin [5-hydroxytryptamine] in the spinal cord. The baseline pain sensitivity did not change following surgery. Analgesia induced by cold swimming stress (CSS), auricular electroacupuncture (AEA) and vaginal probe (VP) was less in A-1-lesioned rats. Using stimulation of high intensity, such as CSS and VP a decrease in pain sensitivity was determined, compared to the baseline. The AEA did not produce such an effect. Catecholaminergic systems of A-1 probably play an important role in pain regulation when CSS, AEA and VP are used. Other neurochemical mechanisms, as well as A-1 nuclei systems, are involved in analgesia, induced by CSS and VP. Lesion of 5-HT-ergic systems of NRM did not have any influence of antinociceptive mechanisms, when activated by AEA and VP.