Abstract
The locus coeruleus (LC) is the largest catecholaminergic nucleus and extensively projects to widespread areas of the brain and spinal cord. The LC is the largest source of noradrenaline in the brain. To date, the only examined Delphinidae species for the LC has been a bottlenose dolphin (Tursiops truncatus). In our experimental series including different Delphinidae species, the LC was composed of five subdivisions: A6d, A6v, A7, A5, and A4. The examined animals had the A4 subdivision, which had not been previously described in the only Delphinidae in which this nucleus was investigated. Moreover, the neurons had a large amount of neuromelanin in the interior of their perikarya, making this nucleus highly similar to that of humans and non-human primates. This report also presents the first description of neuromelanin in the cetaceans’ LC complex, as well as in the cetaceans’ brain.
Highlights
The locus coeruleus (LC) is a densely packed cluster of noradrenaline-producing neurons located in the upper part of the rostral rhombencephalon, on the lateral edge of the fourth ventricle
The LC complex consisted of four divisions (A4, A5, A6, A7), which occupied both the periaqueductal grey (PAG) and the pontine tegmentum (Figs 1–3 and 4)
The presence of the A4 subdivision in the LC is exclusive to certain animals, including humans and non-human primates
Summary
The locus coeruleus (LC) is a densely packed cluster of noradrenaline-producing neurons located in the upper part of the rostral rhombencephalon, on the lateral edge of the fourth ventricle. The LC is the largest catecholaminergic nucleus of the brain, and it supplies noradrenaline to the entire central nervous system. The LC sends projections throughout the brain, including to the neocortex, thalamus, midbrain, hindbrain, cerebellum, and spinal cord[2]. It represents the only source of noradrenaline for these structures[3], and for the cerebral, limbic and cerebellar cortices. The only hitherto examined cetacean species for LC have been the bottlenose dolphin[9], the harbour porpoise (Phocoena phocoena)[10], and the minke whale (Balaenoptera acutorostrata)[11]
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