Effects of idebenone on information processing in aged Long-Evans rats

Coenzyme Q-related compounds to maintain healthy mitochondria during aging

Mitochondrial dysfunction is one of the main factors that affects aging progression and many age-related diseases. Accumulation of dysfunctional mitochondria can be driven by unbalanced mito/autophagy or by decrease in mitochondrial biosynthesis and turnover. Coenzyme Q is an essential component of the mitochondrial electron transport chain and a key factor in the protection of membrane and mitochondrial DNA against oxidation. Coenzyme Q levels decay during aging and this can be considered an accelerating factor in mitochondrial dysfunction and aging progression. Supplementation with coenzyme Q is successful for some tissues and organs but not for others. For this reason, the role of coenzyme Q in systemic aging is a complex picture that needs different strategies depending on the organ considered the main objective to be addressed. In this chapter we focus on the different effects of coenzyme Q and related compounds and the probable strategies to induce endogenous synthesis to maintain healthy aging.

Prefrontal cortex activity patterns during taste neophobia habituation in adult and aged rats

Age-related memory decline has been associated with changes in the medial prefrontal cortex (mPFC) function. In order to explore the role of mPFC in taste recognition memory, we have assessed mPFC c-Fos immunoreactivity in adult (5-month-old) and aged (24-month-old) male Wistar rats during the first (Novel), second (Familiar I), and sixth (Familiar II) exposure to a cider vinegar solution. Adult brains showed higher c-Fos expression in the ventral but not the dorsal region of mPFC during the second taste exposure. Interestingly, old brains exhibited an altered activity pattern selectively in the dorsal peduncular cortex (DP) which can be associated with a delayed attenuation of vinegar neophobia in this group. These results support the involvement of this area in the formation of safe taste memory. Further research is needed for understanding the role of DP in taste recognition memory and the impact of aging on it.

Idebenone inhibition of glutamate release from rat cerebral cortex nerve endings by suppression of voltage-dependent calcium influx and protein kinase A

The present study was aimed at investigating the effect and the possible mechanism of idebenone on endogenous glutamate release in nerve terminals of rat cerebral cortex (synaptosomes). Idebenone inhibited the release of glutamate that was evoked by exposing synaptosomes to the K(+) channel blocker 4-aminopyridine (4-AP), and this phenomenon was concentration dependent. Inhibition of glutamate release by idebenone was prevented by chelating extracellular Ca(2+), or by the vesicular transporter inhibitor bafilomycin A1, but was insensitive to DL-threo-beta-benzyl-oxyaspartate, a glutamate transporter inhibitor. Idebenone decreased the depolarization-induced increase in the cytosolic free Ca(2+) concentration ([Ca(2+)](C)),whereas it did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization. The inhibitory effect of idebenone on evoked glutamate release was prevented by blocking the Ca(v)2.2 (N-type) and Ca(v)2.1 (P/Q-type) channels, but not by blocking intracellular Ca(2+) release or Na(+)/Ca(2+) exchange. Furthermore, the idebenone effect on 4-AP-evoked Ca(2+) influx and glutamate release was completely abolished by the protein kinase A (PKA) inhibitors, H89 and KT5720. On the basis of these results, it was concluded that idebenone inhibits glutamate release from rat cortical synaptosomes and this effect is linked to a decrease in [Ca(2+)](C) contributed by Ca(2+) entry through presynaptic voltage-dependent Ca(2+) channels and to the suppression of PKA signaling cascade.

Colostrinin, a polypeptide isolated from early milk, facilitates learning and memory in rats

Initial observations in humans indicated that colostrinin, a complex of polypeptides derived from the colostrum of sheep, facilitates cognitive functioning in patients with Alzheimer's disease. Its effect on learning and memory in more controlled settings as well as the specificity of these effects were, however, unknown. The present experiments evaluated the effects of colostrinin on spatial learning (Morris water maze) and incidental memory (habituation test) in male Wistar rats of two age groups. Colostrinin, at a dose of 4 microg/rat IP, facilitated acquisition of spatial learning of 13- (aged) but not 3-month-old (young) rats. At the same dose, it improved incidental learning in aged rats, while the dose of 20 microg/rat attenuated it. Colostrinin did not change locomotor activity of rats. Taken together, the present findings indicate that colostrinin may have some beneficial effects on cognitive functioning, particularly in aged subjects. Given the fact that colostrum is the first nutritive agent of neonates, it might be speculated that its peptides may facilitate the early postnatal development of the cerebral neurons and their plasticity.

Protective effects of idebenone and alpha-tocopherol on beta-amyloid-(1-42)-induced learning and memory deficits in rats: implication of oxidative stress in beta-amyloid-induced neurotoxicity in vivo

Amyloid beta-peptide (A beta), the major constituent of the senile plaques in the brains of patients with Alzheimer's disease, is cytotoxic to neurons and has a central role in the pathogenesis of the disease. Previous studies have suggested that oxidative stress is involved in the mechanisms of A beta-induced neurotoxicity in vitro. In the present study, we examined whether oxidative stress contributes to learning and memory deficits caused by continuous intracerebroventricular infusion of A beta-(1-42). In the A beta-(1-42)-infused rats, spontaneous alternation behaviour in a Y-maze and spatial memory in a water maze task were significantly impaired, as compared with A beta-(40-1)-infused control rats. The retention of passive avoidance learning was also significantly impaired by treatment with A beta-(1-42). Potent antioxidants idebenone and alpha-tocopherol prevented the behavioural deficits in Y-maze and water maze, but not passive avoidance, tasks in A beta-(1-42)-infused rats when they were repeatedly administered by mouth once a day from 3 days before the start of A beta infusion to the end of behavioural experiments. Lipid peroxide levels in the hippocampus and cerebral cortex of A beta-(1-42)-infused rats did not differ from those in control animals, and neither idebenone nor alpha-tocopherol affected the lipid peroxide levels. These results suggest that treatment with antioxidants such as idebenone and alpha-tocopherol prevents learning and memory deficits caused by A beta.

Effect of idebenone on in vivo serotonin release and serotonergic receptors in young and aged rats

The effect of idebenone on the serotonergic system was evaluated in the aging rat by measuring the kinetic constants of 3H-5HT and 3H-ketanserin binding sites in the cerebral cortex of rats at 3, 15 and 24 months of age following acute and subchronic administration of the drug. Idebenone displayed no in vitro affinity toward any population of serotonin receptors and did not modify their kinetic parameters after a single dose of 100 mg/kg, at any age tested. A subchronic treatment with the drug for 21 days at the dose of 30 mg/kg did not induce any relevant change in 3- and 15-month-old rats, whereas it significantly increased the density of both 3H-5HT and 3H-ketanserin binding sites in 24-month-old rats, where a lower number of receptors is detected as a consequence of aging. This effect was rather specific, since under the same experimental conditions no changes were detected in the density of cortical beta-adrenergic receptors in aged animals. In microdialysis studies, acute administration with idebenone did not affect 5HT and 5HIAA release at any age. Conversely, the pattern of serotonin metabolism was significantly modified in aged rats following repeated treatment with idebenone and was partially restored to a value similar to the one observed in young animals. These results suggest that idebenone, a putative neuroprotective agent which has been shown to improve brain metabolism in ischemic conditions, might also attenuate age-associated neuronal damage, acting probably on several neurotransmitter systems which undergo selective modification during aging.