Dietary cholesterol alters memory and synaptic structural plasticity in young rat brain

Abstract

Cholesterol plays an important role in synaptic plasticity, learning and memory. To better explore how dietary cholesterol contributes to learning and memory and the related changes in synaptic structural plasticity, rats were categorized into a regular diet (RD) group and a cholesterol-enriched diet (CD) group, and were fed with respective diet for 2 months. Dietary cholesterol impacts on learning and memory, hippocampal synaptic ultrastructure, expression levels of postsynaptic density-95 (PSD-95), synaptophysin (SYP) and cannabinoid receptor type 1 (CB1R) were investigated. We found CD rats had better performances in learning and memory using Morris water maze and object recognition test than RD rats. The memory improvement was accompanied with alterations of synaptic ultrastructure in the CA1 area of the hippocampus evaluated by electron microscopy, enhanced immunoreactivity of SYP, a presynaptic marker in hippocampus detected by immunocytochemistry, as well as increased levels of PSD-95, SYP and decreased level of CB1R in brains of CD rats determined by Western blot. Taken together, the results suggest that the improvement of learning and memory abilities of the young adult rats induced by dietary cholesterol may be linked with changes in synaptic structural plasticity in the brain.

Brain Neuroplastic Changes Accompany Anxiety and Memory Deficits in a Model of Complex Regional Pain Syndrome

“…These data are in agreement with previous findings showing that decreased levels of synaptophysin are accompanied by impairment in cognitive function and memory 84 and vice versa. 85 In contrast, some brain regions (such as the prefrontal cortex) display increased levels of synaptic proteins, 86 including synaptophysin, 87 following chronic painful conditions.…”

Cholesterol and Copper Affect Learning and Memory in the Rabbit

“…For example, increasing cholesterol in mutant mice in which hippocampally dependent spatial learning is normally impaired improves performance in the Morris water maze [88, 89]. Feeding cholesterol to young, normal rats also improves performance in the Morris water maze [90, 91]. Feeding cholesterol to rats that are either deficient in cholesterol or have cholesterol synthesis blocked reverses problems with learning in the water maze and acquisition of eyeblink conditioning [92–95].…”

Dietary cholesterol degrades rabbit long term memory for discrimination learning but facilitates acquisition of discrimination reversal

“…Increasing cholesterol in mutant mice in which hippocampally-dependent spatial learning is normally impaired improves performance in the Morris water maze (Miller & Wehner, 1994; Upchurch & Wehner, 1988). Feeding cholesterol to young, normal rats also improves performance in the Morris water maze (Dufour, Liu, Gusev, Alkon, & Atzori, 2006; Ya et al, 2012). Feeding cholesterol to rats that are either deficient in cholesterol or have cholesterol synthesis blocked reverses problems with learning and memory (Endo, Nishimura, & Kimura, 1996; O'Brien et al, 2002; Voikar, Rauvala, & Ikonen, 2002; Xu et al, 1998).…”

“…Finally, there are a significant number of reports that cholesterol modifies the electrophysiological properties of neurons in the brain particularly the hippocampus (Dufour et al, 2006; Fester et al, 2009; Koudinov & Koudinova, 2001; Parkinson et al, 2009; Tanaka & Sokabe, 2012; Wang & Schreurs, 2010; Ya et al, 2012) and, when studied in the same animals, improves spatial maze learning (Dufour et al, 2006; Ya et al, 2012). Although most of these reports have focused on synaptic plasticity (Koudinov & Koudinova, 2001; Ya et al, 2012), Wang and Schreurs (2010) have shown that a cholesterol diet also has significant effects on the membrane properties of hippocampal neurons including reductions in the size of the afterhyperpolarization – a property that has been shown to be important for learning and memory in rodents and rabbits (Bekisz et al, 2010; Disterhoft & Oh, 2006; Kaczorowski, Sametsky, Shah, Vassar, & Disterhoft, 2009; Kuiper et al, 2012; Matthews, Weible, Shah, & Disterhoft, 2008; Moyer, Jr., Thompson, & Disterhoft, 1996; Tombaugh, Rowe, & Rose, 2005).…”