Hippocampal, Hippocampus

Traumatic brain injury is the most common cause of death in subjects under the age of 40, and an important risk factor for AD. Loss of hippocampal cells and depletion of ACh and of muscarinic receptors can be attenuated in injured experimental animals, improve blood perfusion in ischemic areas and increase cholinergic transmission in cortex and hippocampus the same mechanism invoked for treatment of VD. 

The hippocampus, which got its name from the Greek word for seahorse, due to its form, is a nucleus in the depth of the temporal lobe. The hippocampus is important for the integration of sensory information, for spatial orientation and for memory formation. The hippocampal formation contains the CA (cornu ammonis) regions, the dentate gyms and the subiculum. 

That the hippocampus is important for memory is generally accepted. This is not because it is a site of major degeneration in AzD, that finding can only be used to account for the memory loss if memory is known to be dependent on the hippocampus, but because lesions of that region are known to impair memory. Case reports in the medical literature are rightly mistrusted but few people have felt inclined to disregard the evidence presented by one 27-year-old male mechanic who underwent bilateral hippocampal removal for intractable epilepsy in Montreal in 1953. While that condition was improved the operation has not been repeated because memory loss was almost total, so while he appeared to behave reasonably normally (and still does), he cannot remember where he lives, what he has just eaten or the person he met a few minutes previously. 

We have evaluated the dose-related effects of PCP, ketamine, and selected anticonvulsant drugs on seizure activity in the hippocampal model of kindled seizures. The hippocampal model is particularly well suited for the study of the anticonvulsant effects of drugs because of the slow rate of acquisition of the fully kindled seizure. Electrical stimulation of the dorsal hippocampus initially evokes a stereotyped sequence of behavior, accompanied by a characteristic EEG pattern. Repeated electrical stimulation eventually results in generalized kindled seizures. This allows the testing of drugs on the unkindled hippocampal seizure (afterdischarge) to be compared to effects on the fully kindled seizure in the same rats. 

Male, Sprague-Dawley rats were implanted under pentobarbital anesthesia with a bipolar electrode in the right dorsal hippocampus for hippocampal stimulation and recording. Stainless steel screws were also placed over the contralateral frontal and parietal cortices for recording cortical seizure activity. The electrodes... 

White AM, Matthews DB and Best PJ (2000). Ethanol, memory, and hippocampal function a review of recent findings. Hippocampus, 10, 88-93. 

FIGURE 26-8 Immunohistochemical localization of cAMP response element-binding protein (CREB) in rat hippocampal neurons. Using a polyclonal antibody which recognizes both CREB and phospho-CREB protein, it is apparent that CREB protein is enriched in the nucleus of pyramidal cells of the CA1 region of the hippocampus. Scale bar is 30 pm. (Courtesy of Dr Stephen Ginsberg, Department of Pathology, University of Pennsylvania.)... 

Most importantly, later genetic experiments, using conditional knockout technique to delete all forms of CREB in either the entire forebrain or hippocampus, showed that these conditional knockout mice have normal hippocampal early- and late-phase LTP, and normal performance in hippocampal-dependent memory tasks [13]. Therefore, those newer findings cast significant doubt on the role of CREB as a central switch for long-term plasticity. 

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