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Synthesis, Enzyme Localization, and Regulation of Neurosteroids
Published in Sheryl S. Smith, Neurosteroid Effects in the Central Nervous System, 2003
The majority of patients with medial temporal lobe epilepsy have hippocampal sclerosis as the predominant pathology in their surgical specimens; removal of sclerotic hippocampus cures epilepsy in over 70% of the patients, and during intracranial recordings, seizures originate in the sclerotic hippocampus or closely associated structures (Sloviter, 1994b). For these reasons, mechanisms of epilep-togenesis are extensively studied in the hippocampus. The hippocampus is a threelayered cortex consisting of the cornu ammonis region 1 (CA1), cornu ammonis region 3 (CA3), and dentate gyrus. Pyramidal neurons are the principal neurons in the CA1 and CA3 regions, while granule cells are the primary neurons of the dentate gyrus. A trisynaptic circuit links the three major structures of the hippocampus. The dentate granule cells receive their input from the entorhinal cortex in form of the perforant path and in turn project to CA3 pyramidal neurons via mossy fibers. The CA3 pyramidal neurons project through the fimbria and fornix but also send a large collateral projection (Schaffer collaterals) to the CA1 pyramidal neurons. Each region has a local circuit in which inhibitory and excitatory interneurons participate and mediate feed-forward and feed-back inhibition of the principal neuron.
Stress and Western diets increase vulnerability to neuropsychiatric disorders: A common mechanism
Published in Nutritional Neuroscience, 2021
The CB1 receptors are expressed in the hippocampus, a brain structure that is part of the limbic system, which plays a fundamental role in the inhibitory control of HPA axis activity during adaptation to stressors, as well as in learning and consolidation of episodic memories [26,27]. The morphology of the hippocampus is well-defined, which main three subdivisions include the dentate gyrus, the cornu ammonis (CA) fields (CA1, CA2, CA3), and the subiculum [28]. The hippocampus is a three-layered cortex, consisting of the molecular and cellular layers, as well as polymorph layer [29]. At a neuronal connectivity level, the hippocampus is formed mainly by a trisynaptic circuit formed by a perforant pathway that comes from the entorhinal cortex; these neurons synapse with the dendrites of dentate granule cells from which the mossy fiber projections originate and in turn, synapse with the spines of the CA3 pyramidal cells [29]. The Schaffer collateral projections, that are originated in the CA3, are connected with CA1 pyramidal neurons [29].