Mapeamento de neurônios nitrégicos no tronco encefálico do Mocó (Kerodon rupestris)

Abstract

Nitric oxide (NO) is a gas very important in intra and extracellular process. It is present in many tissues, having an important role in the immunological system, regulation of blood pressure, relaxation of the smooth muscle and vasodilatation through peripheral nervous system. As a gas, NO can pass freely through cell membranes. Therefore, it acts as a neurotransmitter of local action in the central nervous system, reaching short distances, diffusing from cell to cell. It has many functions as learning and memory and modulation of excitatory responses to aminoacids. NO is present in many areas throughout the brain and has been described in many animal species by the expression of its enzyme of synthesis, the NOS. Using immunohistochemistry against NOS and NADPH diaphorase histochemistry we described the distribution of NO in the brainstem of a rodent typical from the Brazilian caatinga, that inhabits rocky areas and has crepuscular habits, the rock cavy (Kerodon rupestris). Several brainstem areas and nuclei presented immunorreactivity to NOS or NADPHd activity. Some of them showed a high density of immunostained neurons, for example the periaqueductal gray, the magnocellular nucleus of the posterior commissure and the interpeduncular nucleus. Others nuclei presented a moderated, as the posterior pretectal nucleus, olivary pretectal nucleus, layers of the superior colliculus and cuneate nucleus. Several showed a low density as the posterior commissure nuclei, paranigral nucleus external cortex of the inferior colliculus and the inferior oliva. Finally, there is nuclei with a very low density, for example the reticular part of the substantia nigra, the pararubral nucleus, the dorsal raphe nucleus, the gracile nucleus and interstitial nucleus of the medulla. The great number of nitrergic nuclei and its pattern of distribution in the rock cavy's brainstem is similar to the other mammals, leading us to conclude that the phylogenetic proximity between species is kept in the brainstem. The present work shows that among other regions the NO is in nuclei of the primary visual system as the pretectal nuclei and the superior coliculum; nuclei of the auditory system as the olivar complex, inferior coliculum and the coclear nuclei; it is in several divisions of the periaqueductal grey matter, strutucture involved in defensive behavior, nociception and anxiety, like the locus coeruleus, where NO also was find; the substantia nigra, where the NO has been related to hepatic encephalopatia and Parkinson's disease in other rodents.The great number of nitrergic nuclei and its pattern of distribution in the rock cavy's brainstem looked alike what is seen in other mammals, leading us to conclude that the philogenetic proximity of the species is mantained in the distribution of NO in the rock cavy's brainstem.