The Distribution and Morphological Characteristics of Catecholaminergic Cells in the Diencephalon and Midbrain of the Bottlenose Dolphin <i>(Tursiops truncatus)</i>

Abstract

The present study describes the distribution and cellular morphology of catecholaminergic neurons in the diencephalon and midbrain of the bottlenose dolphin (Tursiops truncatus). Tyrosine hydroxylase immunohistochemistry was used to visualize these putatively dopaminergic neurons. The standard A1-A17, C1-C3, nomenclature is used for expediency; however, the neuroanatomical names of the various nuclei have also been given. Dolphins exhibit certain tyrosine hydroxylase immunoreactive (TH-ir) catecholaminergic neuronal groups in the midbrain (A8, A9, A10) and diencephalon (A11, A12, A14), however, no neuronal clusters clearly corresponding to the A13 and A15 groups could be identified. The subdivisions of these neuronal groups are in general agreement with those of other mammals, but there is a high degree of species specificity. First, three TH-ir neuronal groups not identified in other species were found: in the ventral lateral peri-aqueductal gray matter, posterior dorsal hypothalamus, and rostral mesencephalic raphe. Second, the normal components of the substantia nigra (A9 or pars compacta, A9 lateral or pars lateralis, A9 ventral or pars reticulata) were extremely cell sparse, but there was a substantial expansion of the A9 medial and A10 lateral subdivisions forming an impressive ‘ventral wing’ in the posterior substantia nigra. The findings of this and previous studies suggest a distinct evolutionary trend occurring in the neuromodulatory systems in mammals. The results are discussed in relation to motor control, thermoregulation, unihemispheric sleep, and dolphin cognition.

Forward shift of feeding buzz components of dolphins and belugas during associative learning reveals a likely connection to reward expectation, pleasure and brain dopamine activation

“…, 1996;Berridge and Robinson, 1998). Dolphins vocalize upon electrical stimulation of reward centers of their brains (Lilly, 1958), which contain dopamine neurons (Manger et al, 2004). We observed numerous forward shifts or transpositions of the terminal portion of a feeding buzz to follow a signal (SR) promising future reward.…”

“…Both rewarding and aversive areas were found in the human brain (Heath, 1963;Bishop et al, 1963). As in the brains of humans, monkeys and rats, there are dopamine neurons in reward areas of dolphin brains (Manger et al, 2004).…”

“…There are dopamine neurons in these areas of the dolphin brain (Manger et al, 2004). Dopamine mediates positive emotions reflected in specific vocalizations.…”

Functional imaging of dolphin brain metabolism and blood flow

“…Modern morphomolecular studies of fixed material have begun to reveal information relative to the neurochemistry of some regions of the dolphin brain (cf. Hof et al, 1995;Glezer et al, 1998;Manger et al, 2003;Manger et al, 2004). However, noninvasive means of investigating this large and highly organized brain in the living animal have been quite limited and there is little understanding of the neurotransmitter and neuromodulator distribution in the dolphin brain as a whole.…”

Nuclear parcellation of certain immunohistochemically identifiable neuronal systems in the midbrain and pons of the Highveld molerat (Cryptomys hottentotus)

“…A recent study in the bottlenose dolphin (Manger et al, 2004) led to the proposal that each order of mammals will have a unique complement of nuclei that make up these neuronal systems. This study demonstrated that while the dolphin had several dopaminergic and noradrenergic nuclei in common with other mammals, there were three nuclei that were unique to the dolphin, and several nuclei commonly found in other mammals that were not evident.…”