Central nucleus of amygdala, locus coeruleus and paraventricular nucleus of dolphins’ brain: where and why?

The brain is still nowadays a great mystery for researchers. Furthermore dolphins’ brain is almost an undiscovered world if we consider the extreme rarity to achieve fresh brain samples of such unique animals with so big brains. There is a great lack of information concerning neuroanatomy of cetaceans. In front of our results (Arbelo, 2007; Herraéz et al., 2007), we have purposed to investigate those nuclei relationated with acute cathecolaminergic stress-response. Massive catecholamine’s liberation from the adrenal glands has been reported in alive stranded cetaceans, as a capture response (alarm reaction) (Cowan and Curry, 2008). But what could trigger such a dramatic reaction? We focused on three nuclei that are known to be involved with the alarm reaction: central nucleus of the amygdaloid complex (NCA), locus coeruleus (LC) and paraventricular nucleus (PVN). Serial 50 μm sections of the amygdaloid complex, hypothalamus and brainstem (at the level of the inferior colliculus) were made using a sliding-microtome with a cooling unit. Sections were later stained for Nissl substance with thionin and immunocytochemically stained for Calbindin (NCA), Tyrosine Hydroxylase (LC) and Vasopressin (PVN) using the free-floating technique. This is a preliminary study; the final goal of our research is to obtain a microscopical description of these nuclei, in order to later detect the expression of some acute stress biomarkers like c-fos and HSP70 (Heat Shock Protein 70).