Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0598853 (forgetting)
 3,232 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous results have indicated the involvement of the hippocampus in the behavioral effect of vasopressin, with a better effect when the peptide was injected in the ventral part rather than in the dorsal part of this structure. The purpose of the present study was to determine, in mice, whether the injection of vasopressin or vasopressin antisera into the ventral hippocampus has an effect on retrieval and relearning of a Go-No Go visual discrimination task and, if so, to what extent this involvement of the vasopressin system depends on the integrity of the medial amygdaloid nucleus, the main source of vasopressin innervation in the ventral hippocampus in rats. In the first experiment, we showed that pretest microinjection of Arg8-vasopressin (25 pg per animal) in the ventral hippocampus alleviated forgetting observed after a prolonged interval of 24 days between the acquisition of information and its retrieval. This enhancing effect was characterized by better retrieval and relearning in vasopressin-treated mice than those in control mice. Conversely, an immunoneutralization of endogenous vasopressin in the ventral hippocampus by the microinjection of vasopressin antisera (1/10 dilution) resulted in the drastic impairment of retrieval and relearning. Since the lack of an observable change in a locomotor activity test might explain these results, we postulated that the vasopressin system in the ventral hippocampus is involved in retrieval processes. Moreover, the effects of these treatments in a nonassociative context suggest that the effect of vasopressin could be dependent on the contextual paradigm used. In the second experiment, we localized vasopressin immunoreactive fibers in the CA1-CA2 ventral hippocampal fields and CA4-gyrus dentatus region, and vasopressin perikarya in the medial amygdaloid nucleus. Then, the projection of vasopressin cells from the medial amygdaloid nucleus to the ventral hippocampus was evaluated by studying changes in vasopressin immunoreactive fiber density in the ventral hippocampus after a lesion of the medial amygdaloid nucleus. The results showed the almost complete disappearance of vasopressin fibers in the CA1-CA2 hippocampal fields after the medial amygdaloid lesion. In contrast, vasopressin fibers in the CA4 and gyrus dentatus region remain unchanged. On the basis of our immunohistochemical results, our third experiment tested the repercussions of the change in vasopressin innervation in the ventral hippocampus, due to the medial amygdaloid lesion, on the effects of exogenously administered vasopressin on both retrieval and relearning processes. The medial amygdaloid lesion induced a deleterious effect on retrieval without really affecting the ability to relearn. No observable change in locomotor activity could explain this impairment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of changes in the intrahippocampal vasopressin on memory retrieval and relearning. 844 31

The hippocampal formation is essential for the processing of episodic memories for autobiographical events that happen in unique spatiotemporal contexts. Interestingly, before 2 years of age, children are unable to form or store episodic memories for recall later in life, a phenomenon known as infantile amnesia. From 2 to 7 years of age, there are fewer memories than predicted based on a forgetting function alone, a phenomenon known as childhood amnesia. Here, we discuss the postnatal maturation of the primate hippocampal formation with the goal of characterizing the development of the neurobiological substrates thought to subserve the emergence of episodic memory. Distinct regions, layers and cells of the hippocampal formation exhibit different profiles of structural and molecular development during early postnatal life. The protracted period of neuronal addition and maturation in the dentate gyrus is accompanied by the late maturation of specific layers in different hippocampal regions that are located downstream from the dentate gyrus, particularly CA3. In contrast, distinct layers in several hippocampal regions, particularly CA1, which receive direct projections from the entorhinal cortex, exhibit an early maturation. In addition, hippocampal regions that are more highly interconnected with subcortical structures, including the subiculum, presubiculum, parasubiculum and CA2, mature even earlier. These findings, together with our studies of the development of human spatial memory, support the hypothesis that the differential maturation of distinct hippocampal circuits might underlie the differential emergence of specific "hippocampus-dependent" memory processes, culminating in the emergence of episodic memory concomitant with the maturation of all hippocampal circuits.
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PMID:Building hippocampal circuits to learn and remember: insights into the development of human memory. 2342 45