Frequency Potentiation in the Medial Cortex of Young Turtle Brains in vitro

Muñoz, Marı́a-Dolores; Magariños-Ascone, C; Gaztelu, J.M.; García-Austt, E.

doi:10.1159/000006571

Cited by 6 publications

(3 citation statements)

References 20 publications

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“…The reptilian medial cortex is considered homologous to the hippocampal formation of mammals and birds on the basis of anatomical and physiological evidence (Northcutt, 1981;Schwerdtfeger and Smeets, 1988;Ulinski, 1990;Muñoz et al, 1998;Nieuwenhuys et al, 1998). In addition, turtles, like mammals and birds, have place-memory capabilities, based on map-like or relational memory representations of the allocentric space.…”

Section: Materials and Methods Experiments 1: Spatial Memory Deficits mentioning

confidence: 99%

Conservation of Spatial Memory Function in the Pallial Forebrain of Reptiles and Ray-Finned Fishes

et al. 2002

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The hippocampus of mammals and birds is critical for spatial memory. Neuroanatomical evidence indicates that the medial cortex (MC) of reptiles and the lateral pallium (LP) of ray-finned fishes could be homologous to the hippocampus of mammals and birds. In this work, we studied the effects of lesions to the MC of turtles and to the LP of goldfish in spatial memory. Lesioned animals were trained in place, and cue maze tasks and crucial probe and transfer tests were performed. In experiment 1, MC-lesioned turtles in the place task failed to locate the goal during trials in which new start positions were used, whereas sham animals navigated directly to the goal independently of start location. In contrast, no deficit was observed in cue learning. In experiment 2, LP lesion produced a dramatic impairment in goldfish trained in the place task, whereas medial and dorsal pallium lesions did not decrease accuracy. In addition, none of these pallial lesions produced deficits in cue learning. These results indicate that lesions to the MC of turtles and to the LP of goldfish, like hippocampal lesions in mammals and birds, selectively impair map-like memory representations of the environmental space. Thus, the forebrain structures of reptiles and teleost fish neuroanatomically equivalent to the mammalian and avian hippocampus also share a central role in spatial cognition. Present results suggest that the presence of a hippocampus-dependent spatial memory system is a primitive feature of the vertebrate forebrain that has been conserved through evolution.

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Section: Materials and Methods Experiments 1: Spatial Memory Deficits mentioning

confidence: 99%

Conservation of Spatial Memory Function in the Pallial Forebrain of Reptiles and Ray-Finned Fishes

et al. 2002

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“…In addition, although experimental data are scarce, medial pallium dependent learning and memory processes in reptiles are likely based on conserved molecular mechanisms. For example, as observed in mammals and birds, both NMDA-dependent and NMDA-independent long-term potentiation have been found in the MC of turtles [46] [47].…”

Section: Medial Pallium or Hippocampus And Map-like Memories In Amniotesmentioning

confidence: 66%

Hippocampal Pallium and Map-Like Memories through Vertebrate Evolution

Broglio¹,

Martín-Monzón²,

Ocaña³

et al. 2015

JBBS

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The hippocampus in humans and other mammals is essential for episodic and relational memories. Comparative evidence indicates that a hippocampal pallium homologue is present in birds, reptiles, amphibians, ray-finned fishes, cartilaginous fishes and agnathans. Some of their characteristics, such as the topological position and the pattern of connectivity, appear remarkably well conserved. We review here substantial data showing that in all the vertebrate groups studied up to date, from fish to mammals, the hippocampus plays a fundamental role in spatial memory. In these vertebrates groups, the hippocampal pallium homologue is involved in the use of map-like, relational representations of the objective space that provide stable allocentric frames of reference, thus allowing flexible navigation. These similarities suggest a common evolutionary ancestry and indicate that the functional properties of the hippocampus appear early in the vertebrate phylogenesis and are retained through the independent evolution of the vertebrate lineages.

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“…Behavioral studies of turtles suggest that their dorsal and medial cortices are implicated in learning and memory ( Lopez et al, 2003a , b ). In the brain of a turtle, the medial cortex in vitro showed frequency potentiation, a type of synaptic plasticity regulated by AMPA receptors ( Muñoz et al, 1998a ). Moreover, long-term potentiation is induced by tetanic stimulation in the medial cortex of the turtle brain, which is also regulated by AMPA receptors ( Muñoz et al, 1998b ).…”

Section: Functional Involvement Of Glutamatergic Neurons In the Brain...mentioning

confidence: 99%

Glutamatergic pathways in the brains of turtles: A comparative perspective among reptiles, birds, and mammals

2022

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Glutamate acts as the main excitatory neurotransmitter in the brain and plays a vital role in physiological and pathological neuronal functions. In mammals, glutamate can cause detrimental excitotoxic effects under anoxic conditions. In contrast, Trachemys scripta, a freshwater turtle, is one of the most anoxia-tolerant animals, being able to survive up to months without oxygen. Therefore, turtles have been investigated to assess the molecular mechanisms of neuroprotective strategies used by them in anoxic conditions, such as maintaining low levels of glutamate, increasing adenosine and GABA, upregulating heat shock proteins, and downregulating KATP channels. These mechanisms of anoxia tolerance of the turtle brain may be applied to finding therapeutics for human glutamatergic neurological disorders such as brain injury or cerebral stroke due to ischemia. Despite the importance of glutamate as a neurotransmitter and of the turtle as an ideal research model, the glutamatergic circuits in the turtle brain remain less described whereas they have been well studied in mammalian and avian brains. In reptiles, particularly in the turtle brain, glutamatergic neurons have been identified by examining the expression of vesicular glutamate transporters (VGLUTs). In certain areas of the brain, some ionotropic glutamate receptors (GluRs) have been immunohistochemically studied, implying that there are glutamatergic target areas. Based on the expression patterns of these glutamate-related molecules and fiber connection data of the turtle brain that is available in the literature, many candidate glutamatergic circuits could be clarified, such as the olfactory circuit, hippocampal–septal pathway, corticostriatal pathway, visual pathway, auditory pathway, and granule cell–Purkinje cell pathway. This review summarizes the probable glutamatergic pathways and the distribution of glutamatergic neurons in the pallium of the turtle brain and compares them with those of avian and mammalian brains. The integrated knowledge of glutamatergic pathways serves as the fundamental basis for further functional studies in the turtle brain, which would provide insights on physiological and pathological mechanisms of glutamate regulation as well as neural circuits in different species.

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Frequency Potentiation in the Medial Cortex of Young Turtle Brains in vitro

Cited by 6 publications

References 20 publications

Conservation of Spatial Memory Function in the Pallial Forebrain of Reptiles and Ray-Finned Fishes

Conservation of Spatial Memory Function in the Pallial Forebrain of Reptiles and Ray-Finned Fishes

Hippocampal Pallium and Map-Like Memories through Vertebrate Evolution

Glutamatergic pathways in the brains of turtles: A comparative perspective among reptiles, birds, and mammals

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