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Biomedical subjects

E Fernández-Espejo

Publications and source records attributed to E Fernández-Espejo.

7 recordsLinked to original sources
PubMed1996

[Basic neurobiology of hippocampal formation].

The hippocampal formation constitutes a SNC region of a great interest for neurobiologists and neurologists, since it plays a key role in cognitive processes such as memory and learning, as revealed by numerous experimental studies and clinical cases. Anatomically, the hippocampus belongs to the archicortex, comprising three neuronal layers. Neighbour regions (gyrus dentatus, subiculum and entorhinal cortex) together with the hippocampus made up the hippocampal formation. Neurochemical studies have revealed the existence of several neurotransmitters such as glutamate, acetylcholine, GABA and catechols. Glutamate and their receptors represent the basis of a phenomenon of long-lasting increase in synaptic efficacy, called long-term potentiation or LTP. Long-term potentiation appears to be a synaptic mechanism related to memory and learning processes. Hippocampus and limbic system as a whole, show a slow electrical rhythm, of an irregular 4-10 Hz pattern, called theta rhythm. Theta rhythm has been proposed to reflect the "gating' of information through the hippocampal circuits. Hippocampal formation is a lamellar region, with a basic trisinaptic circuit, including short and long loops. This structure has led to the connectionist hypothesis, stating that the hippocampus behaves as an autoassociate neural network. Such a hypothesis sheds new lights on how processes such as short-term memory, cognitive mapping, non-association learning and discrimination are carried out within hippocampus.

Electroencephalography↗
PubMed1990

Behavioral study in rats of paired accumbens-lesioned residents and intact intruders.

Behavior in accumbens-lesioned male Wistar rats during paired encounters was assessed by several parameters, scores and cluster analysis based on similarity between patterns. Encounters were videotaped and analyzed by an ethogram and a software package previously elaborated. Residents were lesioned (n = 23) or sham operated (n = 10). A reactivity score was used to corroborate the effectiveness of the lesions. Although accumbens lesions produced the well-known increase in reactivity and enhancement of piloerection, only subtle changes were elucidated by the ethological analysis. Dendrograms revealed postoperative changes in the lesioned rats as well as in the intruders paired with them. Threat category in the lesion group dissociated in threat with arched-back attitude and threat with erect posture. In intruders paired with lesioned rats, compared with those paired with sham-operated animals, the patterns of freezing and on-back became mainly associated with immobile-crouch instead of upright defense posture, and the category of defense/submission was not observed in dendrograms.

Aggression↗
PubMedDate not supplied

[How does the nucleus accumbens function?].

INTRODUCTION: The nucleus accumbens is considered as the neural interface between motivation and action, playing a key role on feeding, sexual, reward, stress-related, drug self-administration behaviors, etc. DEVELOPMENT: The nucleus accumbens possesses two territories, the core and shell, whose connectivity wiring gives a good picture of its motor and limbic aspects. The shell seems to behave as a 'coincidence detector', which can be activated during behavioral situations of adaptive value, thanks to its connections with prefrontal cortex, amygdala and hippocampus. The activation of the shell leads to the reinforcing of goal-directed motor sequences mediated by the core and prefrontal cortex, areas which are, linked to pyramidal and extrapyramidal motor systems. Dopamine secreted within the nucleus accumbens would acts as a 'neurostabilizer' of such processes. CONCLUSION: The nucleus accumbens is made up of an 'electrophysiological coincidence detector' or shell serially connected to a 'motor sequencer' or core, both supporting the role of the nucleus accumbens as a limbic-motor interface.

Animals↗
PubMedDate not supplied

[Neurobiological basis of drug addiction].

INTRODUCTION. Drugs of abuse cause addiction, characterized by compulsive and out of control drug use. Several neurochemical and molecular changes take place in the brain during the first phase of drug use which lead to dependence, addiction and drug abuse. DEVELOPMENT. Every drug of abuse acts through similar neurophysiological mechanisms, mostly based on the abnormal activation of the mesolimbic dopamine system. Although the addicted brain tries to adapted to the drug action, there are permanent neural changes at the cellular and molecular levels which seem to underlie the addictive process and the emergence of abstinence symptoms after drug taking stops. Furthermore, these neural changes appear to subserve the emergence of cravings once the abstinent syndrome has been overcome. Cravings are the main factor leading to relapse, and they are often initiated by exposure to drug related cues.

Brain↗
PubMedDate not supplied

[Natural "dopaminotrophic" cell transplant: a new concept in antiparkinsonian therapy].

AIM AND METHOD: Parkinson s disease is caused by the degeneration of dopaminergic neurons of substantia nigra projecting to striatum. Cellular substitution represents a potentially treatment once beneficial levodopa effects wear off. A promising therapeutic approach is grafting cells or other vectors which release neuroprotective molecules that stimulate regeneration in the damaged nigrostriatal system or, in other words, that exert a dopaminotrophic action. We have tested the suitability of intrastriatal grafts of extra adrenal chromaffin cells taken from the Zuckerkandl s organ. This paraganglion contains chromaffin cells that express and release glial cell line derived neurotrophic factor (GDNF) and transforming growth factor b1 (TGF b1), both known to protect dopamine cells in vitro and in vivo. Grafts induced a functional recovery of parkinsonian rats which developed over months. The beneficial effects of grafts of the Zuckerkandl s organ were related to long survival of grafted cells, striatal reinnervation, enhancement of dopamine levels in the host striatum, and the cell delivery into the host striatum of GDNF and TGF b1. CONCLUSION: Our result should stimulate research on the clinical applicability of transplants of the Zuckerkandl s organ in Parkinson s disease

Animals↗
PubMedDate not supplied

[The neurobiology of psychostimulant addiction].

INTRODUCTION AND DEVELOPMENT: Psychostimulant drugs encompass amphetamines, natural alkaloids like cocaine, and methyl-xanthynes. These drugs induce a strong dependence, manifested as sensitization and tolerance at a neurobiological level. Sensitization is currently being studied experimentally, and it is made up of two stages: initial induction and consolidated expression. During induction, the mesocorticolimbic circuit along with dopamine and glutamate changes in the ventral tegmentum play a critical role. During expression, addictive habits are consolidated through changes in the cortico-striato-amygdaloid loop. CONCLUSION: All together leads to a consolidated addiction, considered as an anomalous learning process, along with a loss of control over drug taking.

Amphetamines↗