Intracerebroventricular insulin improves spatial learning and memory in male Wistar rats.

Abstract

As one of the most studied protein hormones, insulin as well as its receptor have been known to play key roles in a variety of important biological processes. Detection of insulin and its receptor in the central nervous system (CNS) has led to a rapidly growing interest in the central effects of insulin. Insulin and its receptor are located in the specific area of the CNS with a diversity of region-specific functions different from its direct carbohydrate homeostasis in the periphery. The high density of insulin/insulin receptor in brain areas such as the hippocampus and cerebral cortex have shown to play an important role in higher cognitive functions, suggesting that insulin might be involved in the modulation of memory. Previous studies have offered controversial results regarding the effects of insulin on various types of memory. The aim of the present study is to determine whether intracerebroventricular (ICV) administration of insulin improves the water maze performance of rats. The experimental groups had pretraining insulin infusion (2, 4, 8, 16, and 32 mu) into the third ventricle, and then they were compared with a sham (saline) group. Insulin treatment caused an enhancing effect on spatial memory in a dose-dependent manner. The low doses (2, 4, and 8 mu) of insulin had no significant effect on the water maze achievement of rats, whereas higher doses (16 and 32 mu) significantly improved the rats' performance. These results suggest that ICV administration of insulin may result in a dose-dependent improvement of memory function in rats.

Self-regulatory depletion in dogs: Insulin release is not necessary for the replenishment of persistence

“…Given that insulin is critical for neural processes (Mielke, and Wang, 2011), and the administration of insulin to human and nonhuman animals improves cognitive abilities (Haj-ali et al, 2009;Schiöth et al, 2012), glucose induced release of insulin may contribute to replenishment. It is worth noting that cephalic phase insulin responses are elicited when taste receptors activate afferent fibers of the vagus nerve (Teff, 2011).…”

Inflammation, Defective Insulin Signaling, and Mitochondrial Dysfunction as Common Molecular Denominators Connecting Type 2 Diabetes to Alzheimer Disease

“…In cultured hippocampal neurons, IRs show a punctate dendritic synaptic distribution (51,52), and IR signaling regulates synaptic plasticity by controlling synapse density (56). In rodents, IR signaling contributes to long-term memory consolidation and improves spatial learning (81)(82)(83)(84). Insulin has also been proposed to regulate neuronal survival and to act as a growth Supporting the notion that insulin-related signaling plays a central role in learning and memory, impaired insulin sensitivity has been linked to cognitive deficits and structural and functional brain deficits in the elderly (87).…”

The effect of insulin and insulin-like growth factors on hippocampus- and amygdala-dependent long-term memory formation

“…Studies in rodents showed that an intracerebroventricular injection of insulin immediately after inhibitory avoidance (IA) training leads to memory enhancement 24 h after training (Park et al 2000;Babri et al 2007) and that intracerebroventricular or hippocampal injection of insulin enhances spatial working memory and water maze memory (Moosavi et al 2006;Haj-ali et al 2009;McNay et al 2010). To our knowledge, there is no report thus far on the role of IGF1 on memory retention and performance; however, beneficial effects of exercise and recovery from brain insult or neurodegeneration have been shown to involve IGF1, possibly acting through neurogenesis (Aberg et al 2000;Carro et al 2001).…”