DISTRIBUTION HISTAMINERGIC NUCLEI IN HISTAMINE HYPOTHALAMIC ROCK CAVY ( Kerodon rupestris )
Kerodon rupestris, hypothalamus, histamine, histaminergic nuclei, rock cavy, tuberomammillary nucleus.
The rock cavy (Kerodon rupestris) is a crepuscular rodent, native from the Northeast Brazil, being found from Piauí to the north of Minas Gerais, inhabiting rocky regions. It is taxonomically classified as representative of the phylum Chordata, class Mammalia, superorder glires, order Rodentia, suborder Hystricomorpha, family Caviidae and subfamily Caviinae. Histamine is a biogenic amine product of decarboxylation of L-histidine by histidine decarboxylase. It is a neurotransmitter present in the central nervous system neurons, acting in several brain functions, such as regulation of circadian rhythms, feeding behavior, neuroendocrine regulation, energy metabolism, among others. This study aims to delimite histaminergic neuronal nuclei, featuring populations of histamine producing cells in the hypothalamus of the rock cavy. 3 adult young rock cavies were utilized, which were caught in municipalities of Seridó region, in the State of RN (CEUA Protocol 004/2014). The animals were anesthetized, then were perfused, followed by removal of the brain and microtomy into 6 series of 30 micrometers coronal sections, which were stored in 0.1 M phosphate buffer, pH 7.4. One series sections were subjected to Nissl staining method using the Thionin dye. Another series was subjected to immunohistochemistry for the detection of histamine (HIS), using anti-histamine as a marker, by the avidin-biotin-peroxidase protocol (ABC). It was used an anti-histamine primary antibody obtined in rabbit, a biotinylated secondary antibody against rabbit obtained in donkey and the avidin-biotin-HRP complex. The visualization of the reaction occurred by the contact of the sections with the tetrahydrochloride-diaminobenzina (DAB) and hydrogen peroxide (H2O2). The sections were mounted on slides and qualitatively analyzed by optical microscopy and the results regarding the distribution of histamine neuronal groups were documented through description and digital photomicrographs. The data presented are based in the analysis of one case, in which it was possible to evidence histamine immunoreactive (HIS-IR) neurons, filling the ventral tuberomammillary (VTM), dorsal tuberomammillary (DTM), ventral premammillary (PMV) and medial mammillary (MM) nuclei, which may be grouped as part of the tuberomammillary complex. The topographic distribution of histamine neuronal groups in the rock cavy hypothalamus resembles that of other rodents, such as like rat and mouse, suggesting that this is an evolutionarily conserved neurotransmitter system.