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Assessment of Second Messenger Function in the Hippocampus of Aged Rats with Cognitive Impairment
Published in David R. Riddle, Brain Aging, 2007
Michelle M. Nicolle, Hai-Yan Zhang, Jennifer L. Bizon
The animal model that we have used to investigate the behavioral relevance of age-related changes in signal transduction mechanisms is reliable and well-established [9, 10]. Briefly, hippocampal-dependent spatial memory is assessed in young and aged male Long-Evans rats in the Morris water maze. Using data from probe trials that are interpolated throughout our training protocol, an individual measure of spatial learning ability is derived for each rat (i.e., a “spatial learning index”). As shown in Figure 9.1, plotting individual young and aged rat spatial performance using the spatial learning index reveals that this measure reliably distinguishes two groups of aged rats: (1) those that learn on par with the young cohorts (i.e., aged-unimpaired rats) and (2) those that perform outside the range of young rats, demonstrating impairment on the task (i.e., aged-impaired rats) [9]. The variability in spatial learning performance observed in this population of aged rats both mimics that observed in humans and affords investigators the opportunity to not only compare neurobiological factors that change as a function of age but, also, to directly link such changes to a functional behavioral measure of hippocampal integrity. Among aged rats, the correlation between individual learning indices and neurobiological measures related to the efficacy of signal transduction mechanisms is the primary methodology used in our studies. Although all data in this chapter are related to this one particular model, both the neurobiological and behavioral changes have been replicated in other strains of rodents and even primates. The approaches and techniques described here should be useful and applicable to other animal models of cognitive aging.
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
It has been posited that different memory systems, including spatial memory, emerged as adaptive specialization (see ADAPTATION) to deal with specific problems animals were required to solve in order to survive. An adaptive specialization of a memory system is characterized by rules of operation that makes it especially suitable for a solution of a particular environmental problem, while poorly suited for the solving of other problems (see Sherry & Schacter, 1987). Thus, it is possible that different forms of spatial memory emerged in response to different problems of NAVIGATION, each of which required a specialized memory subsystem to solve the particular type of problem. There is evidence to suggest that different forms of spatial memory are subserved by distinct and largely independent neural systems. For example, the HIPPOCAMPUS appears to be involved in cognitive-map-based spatial memory, but not in egocentric or allocentric spatial memory. Likewise, the CAUDATE NUCLEUS may be more involved in egocentric and simple allocentric spatial memory, but not in the use of a cognitive map. Moreover, it appears that these different memory systems can learn to solve a spatial memory task simultaneously and independently of each other. In one study (Packard & McGaugh, 1996), rats were trained on a task that could be solved using either an allocentric spatial strategy or an egocentric strategy. On a probe day, rats were given reversible LIDOCAINE-induced inactivation (see TRANSIENT LESIONS) of either the hippocampus or the caudate nucleus. Inactivation of the hippocampus biased rats to use an egocentric strategy, while similar inactivation of the caudate nucleus biased rats to use an allocentric spatial strategy. These data suggested that separate spatial memory systems that govern egocentric and cognitive map-based spatial learning are able to solve spatial problems independently, and in parallel to each other.
Sexual Differentiation of Spatial Functions in Humans
Published in Akira Matsumoto, Sexual Differentiation of the Brain, 2017
Experimental studies in the rat have shown that the male advantage normally observed on conventional spatial learning tasks like the Morris water maze (WM) or radial-arm maze (RAM) is powerfully dependent on sex steroids. Early studies involving neonatal hormone manipulations4,37,38 indicated a possible role for sex hormones in the organization of spatial learning. But these studies were not followed up in detail until nearly 1990. In an elegant set of experiments, Williams et al.39 showed that exposing female rats to estradiol benzoate (EB) in the first few days of life led to male-typical levels of maze acquisition in adulthood and changes in the relative reliance on landmark vs. geometric cues for navigation in the RAM. Females exposed to neonatal estrogen showed improved performance relative to control females and increased reliance on geometry cues, a change toward the typical male pattern of performance. In later work using a different type of maze, Roof40 found a dose-dependent improvement in both the RAM and WM in female rats treated neonatally with T propionate (TP), and also found evidence of a reverse effect in males, consistent with the optimal level hypothesis and with our own findings for spatial ability in boys with CAH. The hippocampal formation is often considered to be one important substrate for this form of spatial learning in the rat. It was therefore of interest that Roof and Havens41 observed morphological changes in the granule cell layer (GCL) of the dentate gyrus in response to neonatal TR Females treated with TP showed a wider GCL than control females, as is more typical of males. A larger GCL predicted better maze acquisition in females. The Roof and Williams studies implicate the first few neonatal days as a sensitive period for masculinization of spatial function in the rat and suggest that this masculinization occurs via the aromatization route.
The role of the mucin-glycan foraging Ruminococcus gnavus in the communication between the gut and the brain
Published in Gut Microbes, 2022
Erika Coletto, Dimitrios Latousakis, Matthew G. Pontifex, Emmanuelle H. Crost, Laura Vaux, Estella Perez Santamarina, Andrew Goldson, Arlaine Brion, Mohammad K. Hajihosseini, David Vauzour, George M Savva, Nathalie Juge
Spatial learning and memory were evaluated through the Barnes Maze as described previously but with slight modifications.107,108 Briefly, the maze was brightly illuminated (800 lux lighting), and the animal was placed onto the circular platform (92 cm diameter) and was trained to find the designated escape box among the 20 evenly distributed holes located around the circumference using visual cues (4 simple shapes) placed around the periphery. The experiment was conducted over a 3-day period, with training consisting of 7 trials on days 1 and 2. On day 3, a probe test was conducted, the maze was rotated 90°, the escape box was removed, and mice were placed in the center of the maze in which they were free to navigate for 90 sec. The percentage time in the correct quadrant was determined using Ethovision software (UK).
Effect of dihydromyricetin on hepatic encephalopathy associated with acute hepatic failure in mice
Published in Pharmaceutical Biology, 2021
Long Cheng, Xiaoying Wang, Xueni Ma, Huimei Xu, Yifan Yang, Dekui Zhang
Spatial learning and memory function were assessed using the Morris water maze test (Zhan et al. 2019). Briefly, mice were trained four times each day for five consecutive days in a circular pool where each mouse was permitted 60 s to find the hidden platform, which was 10 cm in diameter and submerged 1 cm below the water surface in the target quadrant. If the mice failed to locate the platform, they were guided to the platform and remained there for 15 s in order to ensure that each mouse could successfully find the platform after training. On the sixth day, we removed the platform and subjected the mice to a 60 s probe trial, which was recorded and used to evaluate reference spatial memory. We used a digital video camera (WMT-100S Morris, Chengdu Taimeng Software Co., Ltd, CN) to record the number of times the mice crossed the platform area (platform crossing).
Antidepressants Promote and Prevent Cancers
Published in Cancer Investigation, 2020
Francis Lavergne, Therese M. Jay
BDNF administration modulates mood, memory and neurogenesis in the brain. Intra-peritoneal administration of the TAT-BDNF fusion peptide (the core functional domain of BDNF and the membrane-penetrating TAT) improves learning and memory in two Alzheimer disease-like rodent models. Spatial learning and memory were tested using the Morris water maze test. Administration of the TAT-BDNF peptide reduces the latency to find the platform and increases the time and path length in the target quadrant. The number of dendritic spines and the percentage of mushroom-shaped spines were significantly increased in treated rats. TAT-BDNF peptide can remodel synaptic plasticity. The mechanisms involve activation of the TrkB/Erk/Akt signaling pathway (193). These effects are similar to the effects of physical exercise on mood, memory and neurogenesis.