IDENTIFICATION OF THE PREMAMMILLARY NUCLEI IN ROCK CAVY (Kerodon rupestris): CYTOARCHITECTURE AND IMMUNOHISTOCHEMISTRY AGAINST NOS
Hypothalamus; Ventral premammillary nucleus; Dorsal premammillary nucleus; Nitric oxide synthase.
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 drop-shaped 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. 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.