Brain Imaging in Depression and Anxiety
Siegfried Kasper, Johan A. den Boer, J. M. Ad Sitsen in Handbook of Depression and Anxiety, 2003
More recently, 1H MRS has been used to investigate whether there is evidence of hippocampal damage following ECT on the basis that neuronal damage may show up as a reduction of NAA signal [63]. No changes were detected after ECT, suggesting that ECT is unlikely to induce hippocampal atrophy or cell death. The study also measured Cho levels in the right and left hippocampus of the depressed patients before ECT and compared them with a group of healthy controls and remitted depressed patients treated with amitriptyline. Cho levels were found to be lower bilaterally in the depressed patients and increased following ECT, which corresponded with clinical response. The authors suggest that this represents increased membrane turnover as a result of ECT treatment. These findings are concordant with rat experiments in which repeated seizures of the hippocampal-parahippocampal circuits can cause mossy fiber sprouting without cell death [64]. The authors speculate that the Cho signal increase after ECT treatment might similarly reflect mossy fiber sprouting in hippocampal subfields.
Histamine as Neurotransmitter
Divya Vohora in The Third Histamine Receptor, 2008
The histamine effects on PKA signaling, ion channel function, and neuronal excitability have been analyzed in synaptic isolation (low Ca2+, high Mg2+) [175]. Histamine has bidirectional effects on pyramidal cell firing in the CA1 region, an initial and short-lasting depression (H1R) followed by a long-lasting (>2 h) excitation (H2R). This excitation was less effective than a coincident activation of both H1R and H2R [164,175,189]. In addition, histamine causes a long-lasting enhancement of synaptically evoked population spikes in the CA1 and CA3 regions through H2R activation [304] (Figure 3.7). A postsynaptic effect of H2R in CA3 enhances the response to glutamate released at the mossy fiber synapse [305]. CA3 pyramidal cells synchronize themselves and discharge in bursts (Figure 3.10), which can be recorded as sharp waves in the EEG. This is an important effect in light of the decisive role of CA3 synchronization in synaptic plasticity and memory trace formation [306].
Transmitter Glutamate in Mammalian Hippocampus and Striatum
Elling Kvamme in Glutamine and Glutamate in Mammals, 1988
The mossy fibers show a specific labeling with d-aspartate or l-glutamate at the electron microscopic level.18 The uptake was not very dense compared with the other layers, but it became very distinct after kainic acid treatment, which removes the pyramidal cells in CA3 and thereby the labeling in surrounding structures.17 Also, retrograde transport of d-aspartate has been shown to occur from the mossy fiber region to the granular cells.31 Since the mossy fibers occupy such a small part of the CA3 region, it has not been possible to demonstrate any effect on release and uptake of glutamate and aspartate in CA3 region after destruction of the mossy fibers.20 The reason for the scattered uptake of d-aspartate in the mossy fibers may be due to the mechanical disruption of these large terminals in a slice or that only a part of them are glutamatergic/aspartatergic. The mossy fibers have been demonstrated to also contain enkephalin.32,33,71 The mossy fibers also show heavy TIM staining (TIMs sulfide silver method) and have a high concentration of Zn.34 Stimulation of granule cells through the activation of the perforant path was accompanied by a reduction in TIM staining of the mossy fiber.35 This has given rise to speculation on a coupling between Zn and transmitter glutamate, particularly during epilepsy.
Rat hippocampal CA3 neuronal injury induced by limb ischemia/reperfusion: A possible restorative effect of alpha lipoic acid
Published in Ultrastructural Pathology, 2018
Ola A. Hussein, Amel M. M. Abdel-Hafez, Ayat Abd el Kareim
Ultrastructural examination reveals the typical morphology of its main neuron type, i.e., the pyramidal neurons. These neurons have large rounded euchromatic nuclei with finely dispersed chromatin and prominent nucleoli. The surrounding cytoplasm contains numerous mitochondria, numerous RER and free ribosomes, well-developed Golgi complex in addition to lysosomes and multivesicular bodies (Figure 2(a)). The apical dendrites of these neurons project into stratum lucidum intervened with mossy fiber axons and large mossy fiber terminals. The dendrite cytoplasm appears electron lucent with numerous well-organized microtubules and mitochondria. These dendrites make synaptic contacts with the large mossy fiber that appear more electron-dense and contain numerous synaptic vesicles (Figure 2(b)). Typically, astrocytes have oval euchromatic nucleus with a thin rim of peripheral heterochromatin. Their thin perikaryon contains few organelles as mitochondria and Golgi (Figure 2(c)). The blood capillaries are lined by thin endothelial cells that have flattened nuclei with clumps of heterochromatin. Their thin cytoplasm contains few organelles. The surrounding basal lamina appears thin and regular (Figure 2(d)).
Aberrant plasticity in the hippocampus after neonatal seizures
Published in International Journal of Neuroscience, 2018
Xiaoqian Zhang, Huiling Qu, Ying Wang, Shanshan Zhao, Ting Xiao, Chuansheng Zhao, Weiyu Teng
Similar to adult seizures, basal dendrites had been seen after neonatal seizures. For example, Shapiro viewed double-cortin-labeled cells by immunoelectron microscopy and sought evidence of abnormal morphology of dendrites from newly formed DGCs. They found a robust synapse formation between mossy fiber terminals and basal dendrites of newly formed DGCs in animals experienced neonatal hypoxia. Instead, no such synapses were observed in sham animals [67]. Sanchez et al. demonstrated robust synapse formation on hilar basal dendrites in rats subjected to neonatal hypoxia, whether or not the rats had experienced tonic–clonic seizures during the hypoxic event. Based on the appearance of dense core vesicles, the axon terminals that synapsed onto hilar basal dendrites were identified as mossy fiber terminals [68]. Wang et al. also showed that more basal dendrites were observed in those rats that had experienced hypoxia-induced neonatal seizures; this might represent an anatomic substrate for increased seizure susceptibility and the development of epilepsy [47]. GABA, Na+-K+−2Cl− cotransporter 1 and K+-Cl− cotransporter 2.
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].
Related Knowledge Centers
- Axon
- Dentate Gyrus
- Glutamic Acid
- Granule Cell
- Hippocampus
- Myelin
- Hippocampus Anatomy
- Short-Term Memory
- Stratum Lucidum of Hippocampus
- Immunohistochemistry