Identificação dos núcleos pré-familiares em Mocó (Kerodon rupestris): citoarquitetura e imunoistoquímica para NOS

Abstract

The hypothalamus is a part of the diencephalon responsible for many homeostatic proccess essential to life. Inside the mammillary area, the premammillary area is characterized by the presence of two nuclei, the ventral premammillary nucleus (PMV) and the dorsal premammillary nucleus (PMD). The PMV is very important to the circuits that control many reproductive and aggressive aspects, while the PMD is very important to the circuit that control defensive and agonistic behavior. In rodents, as rat and mouse, the PMV is a dropshaped compact group of neurons in a rostral level, but is rounded in a caudal level. The PMD is caudal and dorsal to the PMV and has a rectangular shape in a rostral level, being more rounded in a caudal level when the medial mammillary nucleus appears. Functional studies showed a subdivision in the PMD, with a ventrolateral part (PMDvl) involved with defensive behavior against predator, and the dorsomedial parte (PMDdm) involved with social agonistic behavior. The present work aimed to study the premammillary nuclei in the hypothalamus of the rock cavy (Kerodon rupestris), an endemic rodent of the Brazil’s Northeast. To do so, we used Nissl staining and immunohistochemistry against the nitric oxide synthase (NOS). Both methods of staining showed the presence of the PMV and PMD in the rock cavy’s hypothalamus with location and morphology very similar to the rat. However, the rostral level of the rock cavy’s PMV seems to be more rostral than what is seen in other rodents where the the PMV appears only after the division of the third ventricle. Besides that, the NOS staining showed the PMDdm and the PMDvl, what was reported before rat only by functional studies. We concluded that the premammillary nuclei in rock cavy have features that point them as participant in circuits that control behaviors as reproduction, aggression and defense.