Distribution of glycine immunoreactivity in the brain of the Siberian sturgeon (Acipenser baeri): comparison with γ-aminobutyric acid.
ABSTRACT Glycine and γ-aminobutyric acid (GABA) are the main inhibitory neurotransmitters in the central nervous system (CNS) of vertebrates. Studies on the distribution of glycinergic neurons and fibers have been carried out mainly in rodents and lampreys. With the aim of discovering more about the early evolution of this system in vertebrates, we analyzed the distribution of glycine-immunoreactive (Gly-ir) neurons and fibers in the CNS of a basal ray-finned fish, the Siberian sturgeon (Chondrostei, Acipenseriformes), by use of immunohistochemical techniques. We also compared the distribution of glycine and GABA by the use of double-immunofluorescence techniques and confocal microscopy. Our results revealed the presence of Gly-ir cells in different regions of the CNS, such as olfactory bulbs, preoptic area, hypothalamus, thalamus, pretectum, optic tectum, tegmentum and rostral spinal cord, although most of the Gly-ir cells and the most intensely immunoreactive cells were located in the rhombencephalon, mainly in the octavolateral area and reticular formation. In addition, coronet cells of the basal hypothalamus and saccus vasculosus were Gly-ir. Glycinergic fibers coursed along most brain regions and were more abundant in the thalamus, hypothalamus, optic tectum, tegmentum, isthmic region, and basal rhombencephalon. The Mauthner cell perikaryon was richly innervated by Gly-ir boutons, as reported for teleosts. With regard to the colocalization of glycine and GABA, double-immunoreactive cells were located mainly in the rhombencephalon. The results enable us to conclude that the distribution of glycine in the sturgeon brain is more similar to that observed in lampreys than that observed in mammals.
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ABSTRACT: Although the neuroanatomical distribution of catecholaminergic (CA) neurons has been well documented across all vertebrate classes, few studies have examined CA connectivity to physiologically and anatomically identified neural circuitry that controls behavior. The goal of this study was to characterize CA distribution in the brain and inner ear of the plainfin midshipman fish (Porichthys notatus) with particular emphasis on their relationship with anatomically labeled circuitry that both produces and encodes social acoustic signals in this species. Neurobiotin labeling of the main auditory endorgan, the saccule, combined with tyrosine hydroxylase immunofluorescence (TH-ir) revealed a strong CA innervation of both the peripheral and central auditory system. Diencephalic TH-ir neurons in the periventricular posterior tuberculum, known to be dopaminergic, send ascending projections to the ventral telencephalon and prominent descending projections to vocal-acoustic integration sites, notably the hindbrain octavolateralis efferent nucleus, as well as onto the base of hair cells in the saccule via nerve VIII. Neurobiotin backfills of the vocal nerve in combination with TH-ir revealed CA terminals on all components of the vocal pattern generator which appears to largely originate from local TH-ir neurons but may include diencephalic projections as well. This study provides strong evidence for catecholamines as important neuromodulators of both auditory and vocal circuitry and acoustic-driven social behavior in midshipman fish. This first demonstration of TH-ir terminals in the main endorgan of hearing in a non-mammalian vertebrate suggests a conserved and important anatomical and functional role for dopamine in normal audition. J. Comp. Neurol., 2014. © 2014 Wiley Periodicals, Inc.The Journal of Comparative Neurology 04/2014; · 3.66 Impact Factor
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ABSTRACT: Vocal communication has emerged as a powerful model for the study of neural mechanisms of social behavior. Modulatory neurochemicals postulated to play a central role in social behavior, related to motivation, arousal, incentive and reward, include the catecholamines, particularly dopamine and noradrenaline. Many questions remain regarding the functional mechanisms by which these modulators interact with sensory and motor systems. Here, we begin to address these questions in a model system for vocal and social behavior, the plainfin midshipman fish (Porichthys notatus). We mapped the distribution of immunoreactivity for the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) in the midshipman brain. The general pattern of TH(+) cell groups in midshipman appears to be highly conserved with other teleost fish, with a few exceptions, including the apparent absence of pretectal catecholamine cells. Many components of the midshipman vocal and auditory systems were innervated by TH(+) fibers and terminals, including portions of the subpallial area ventralis, the preoptic complex, and the anterior hypothalamus, the midbrain periaqueductal gray and torus semicircularis, several hindbrain auditory nuclei, and parts of the hindbrain vocal pattern generator. These areas thus represent potential sites for catecholamine modulation of vocal and/or auditory behavior. To begin to test functionally whether catecholamines modulate vocal social behaviors, we hypothesized that male and female midshipman, which are sexually dimorphic in both their vocal-motor repertoires and in their responses to hearing conspecific vocalizations, should exhibit sexually dimorphic expression of TH immunoreactivity in their vocal and/or auditory systems. We used quantitative immunohistochemical techniques to test this hypothesis across a number of brain areas. We found significantly higher levels of TH expression in male midshipman relative to females in the TH cell population in the paraventricular organ of the diencephalon and in the TH-innervated torus semicircularis, the main teleost midbrain auditory structure. The torus semicircularis has been implicated in sexually dimorphic behavioral responses to conspecific vocalizations. Our data thus support the general idea that catecholamines modulate vocal and auditory processing in midshipman, and the specific hypothesis that they shape sexually dimorphic auditory responses in the auditory midbrain.Journal of chemical neuroanatomy 01/2014; · 1.75 Impact Factor
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ABSTRACT: The potential for “replacement cells” to restore function in Parkinson's disease has been widely reported over the past 3 decades, rejuvenating the central nervous system rather than just relieving symptoms. Most such experiments have used fetal or embryonic sources that may induce immunological rejection and generate ethical concerns. Autologous sources, in which the cells to be implanted are derived from recipients' own cells after reprogramming to stem cells, direct genetic modifications, or epigenetic modifications in culture, could eliminate many of these problems. In a previous study on autologous brain cell transplantation, we demonstrated that adult monkey brain cells, obtained from cortical biopsies and kept in culture for 7 weeks, exhibited potential as a method of brain repair after low doses of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) caused dopaminergic cell death. The present study exposed monkeys to higher MPTP doses to produce significant parkinsonism and behavioral impairments. Cerebral cortical cells were biopsied from the animals, held in culture for 7 weeks to create an autologous neural cell “ecosystem” and reimplanted bilaterally into the striatum of the same six donor monkeys. These cells expressed neuroectodermal and progenitor markers such as nestin, doublecortin, GFAP, neurofilament, and vimentin. Five to six months after reimplantation, histological analysis with the dye PKH67 and unbiased stereology showed that reimplanted cells survived, migrated bilaterally throughout the striatum, and seemed to exert a neurorestorative effect. More tyrosine hydroxylase‐immunoreactive neurons and significant behavioral improvement followed reimplantation of cultured autologous neural cells as a result of unknown trophic factors released by the grafts. J. Comp. Neurol. 522:2729–2740, 2014. © 2014 Wiley Periodicals, Inc. We biopsied the cerebral cortex of live St. Kitts green monkeys, then cultured and reimplanted the cells into the original hosts to reverse severe MPTP‐induced parkinsonism. The numbers of tyrosine hydroxylase‐expressing cells and behavior improved in almost all test animals, even with extremely low numbers of surviving graft cells.The Journal of Comparative Neurology 01/2014; 522(12). · 3.66 Impact Factor