Hippocampal dentate granule cells

There have been a number of observations which show increased excitation and/or reduced inhibition in slices prepared from human epileptic brain tissue. Thus burst discharges can be evoked with stimuli that would not do so in normal animal tissue and these can be blocked by NMD A receptor antagonists. The inhibitory postsynaptic currents (IPSCs) in hippocampal dentate granule cells in slices prepared from temporal lobe epileptic tissue are in fact reduced by stimulation that activates NMDA currents (Isokawa 1996), which are more prolonged than usual and show changes in slope conductance. 

Alfano DP, Petit TL. 1982. Neonatal lead exposure alters the dendritic development of hippocampal dentate granule cells. Exp Neurol 75 275-288. 

ZnT-2, a component of vesicular acid intracellular compartments, is predominantly expressed in intestine, kidney, and testis and is scarcely detected in brain in mice (Palmiter et al., 1996). Overexpression of ZnT-2 in baby hamster kidney cells conferred resistance to elevated Zn with sequestration into acidic compartments at higher concentrations (Palmiter et al 1996). In contrast, coexpression of ZnT-1 suppressed ZnT-2 mediated transport into acidic vesicles suggesting ZnT-2 has a relatively low affinity for Zn and functions only under excessive elevations of Zn as a second line of defense when other ZnTs fail to function properly (Palmiter et al., 1996). ZnT-3 sequesters Zn in vesicles and has expression limited to brain and testis (Palmiter et al., 1996). In mouse brain, ZnT-3 is associated with hippocampal dentate granule cells, pyramidal, and intraneurons as evidenced by levels of mRNA (Palmiter et al., 1996). 

Herman ST, Kapur J, MacDonald RL. Rapid seizure-induced reduction of benzodiazepine and sensitivity of hippocampal dentate granule cells. J Neurosci 1997 17 7532-7540. 

The effect of serotonin on synaptogenesis is not limited to the sensory cortex, as it has also been reported that reduction of serotonin in the early postnatal period can result in changes in the morphology of hippocampal dentate granule cells, particularly at the level of the synapse, as reflected by the permanent reduction in synaptic spine density [80]. 

Possible relationship to hippocampal dysfunction. Behav. Neural Biol, 32, 319 Alfano, D. P. and Petit T. L. (1982). Neonatal lead exposure alters the dendritic development of hippocampal dentate granule cells. Exp. Neurol, 75, 275 Anden, N. E., Robenson, A., Fuxe, K. and Hokfelt, T. (1967). Evidence for dopamine receptor stimulation by apomorphine. J. Pharm. Pharmacol, 19, 627 Angell, N. F. and Weiss, B. (1982). Operant behavior of rats exposed to lead before or after weaning. Toxicol Appl Pharmacol, 63, 62 Archer, J. (1973). Tests for emotionality in rats and mice a review. Animal Behav., 21, 205... 

A morphometric examination of the hippocampal mossy fiber system (the axons of the hippocampal dentate granule cells) following Pb exposure during development was carried out by Alfano et al. The development of this axonal system is of particular interest since this pathway sequesters the largest amount of Pb in the normal brain, and forms a major internal circuit in the hippocampus. The authors report that high Pb exposure causes reductions in the development of this pathway, even in the absence of any differences in brain weights. 

Deng W, Saxe MD, Gallina IS (2009) Adult-born hippocampal dentate granule cells undergoing maturation modulate learning and memory in the brain. J Neurosci 29 ... 

Fig. 24. Di receptor immunoreactivity in parietal cortex (A and B), cingulate cortex (C and D), hippocampal formation (E-G) and medial dorsal nucleus of the thalamus (H). In A and C, the numbers identify cortical layers and boxed areas are shown in B and D, respectively. Arrow in G identifies labeled dentate granule cells. Bars = 100 pm (A, C and E) or 50 pm (B, D and F H). Reproduced with permission from Huang et al. (1992).

The D3 receptor was also found in the hippocampal formation (granule cell layer of the dentate gyrus) and in the amygdaloid complex (anterior, basomedial and medial nuclei). In the posterior hypothalamus, D3 receptor was found to be expressed in the medial mammillary nucleus (Bouthenet et al., 1991). 

Dudek, F., Obenaus, A., Schweitzer, J., Wuarin, J. (1994). Functional significance of hippocampal plasticity in epileptic brain electrophysiological changes of the dentate granule cells associated with mossy fiber sprouting. Hippocampus 4 259-65. 

It is important to consider the optimal time to perform an experiment Slice cultures change continuously in vitro. The development of the hippocampal slice in vitro has not been extensively studied. Extracellular recordings have shown that synaptic responses are substantially lai]ger at 21 than at 7 DIV (3). The mossy fiber pathway connecting dentate granule cells with CA3 pyramidal cells and hilar intemeurons forms entirely in vitro between 14 and 21 DIV (4,5,7). After 28 DIV, a steadily increasing proportion of cultures will be spontaneously epileptic see Note 14). As a result, we perform most experiments between 21-28 DIV. This permits mossy fiber development, yet avoids spontaneous epileptiform activity. 

Hippocampal mossy fibres, which are the axons of dentate granule cells, converge in the dentate hilus and innervate hilar and CA3 neurons (Frotscher et al., 1994). In the rodent, the main mossy fibre axons leave the hilus and travel through CA3... 

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