The role of adult brain neurogenesis (generating new neurons) in learning and memory appears to be quite firmly established in spite of some criticism and lack of understanding of what the new neurons serve the brain for. Also, the few experiments showing that blocking adult neurogenesis causes learning deficits used irradiation and various drugs known for their side effects and the results obtained vary greatly. We used a novel approach, cyclin D2 knockout mice (D2 KO mice), specifically lacking adult brain neurogenesis to verify its importance in learning and memory. D2 KO mice and their wild-type siblings were tested in several behavioral paradigms, including those in which the role of adult neurogenesis has been postulated. D2 KO mice showed no impairment in sensorimotor tests, with only sensory impairment in an olfaction-dependent task. However, D2 KO mice showed proper procedural learning as well as learning in context (including remote memory), cue, and trace fear conditioning, Morris water maze, novel object recognition test, and in a multifunctional behavioral system-IntelliCages. D2 KO mice also demonstrated correct reversal learning. Our results suggest that adult brain neurogenesis is not obligatory in learning, including the kinds of learning where the role of adult neurogenesis has previously been strongly suggested.New neurons are produced in the brains of adult animals, including humans, throughout their lifespan (Altman 1963;Eriksson et al. 1998). Since one of the sites of adult brain neurogenesis is hippocampal formation, a brain structure involved in learning and memory, new neurons were expected to be involved in these phenomena. Following years of research, adult brain neurogenesis, along with synaptic strengthening, synaptic elimination/ weakening, and synaptogenesis are now regarded as four major types of plasticity required for formation and retention of memories (Bruel-Jungerman et al. 2007). However, the very evidence for the role of adult hippocampal neurogenesis in learning and memory remains limited, and in most cases, indirect (Leuner et al. We showed before (Kowalczyk et al. 2004) that cyclin D2, a protein involved in cell cycle regulation, is the only cyclin D (out of D1, D2, and D3) expressed in wild-type (WT) hippocampal neuronal progenitors expanded in vitro into neurospheres. Furthermore, careful analysis of the brains of cyclin D2 knockout mice (D2 KO mice) failed to reveal BrdU-positive neurons in the dentate gyrus of the hippocampal formation. We were also unsuccessful in increasing the number of newly generated cells in the hippocampus by a variety of stimulations, including introducing the mice to a novel environment, or even by a local brain injury. Notably, while adult brain neurogenesis of D2 KO mice is missing, their developmental neurogenesis allows for the formation of the brain, with all of the major structures present, though some of them are smaller. Also, neurogenesis outside of the central nervous system seems to be unaffected in these mice (Kowalczyk et al. 20...

Protocatechuic acid has very promising properties potentially useful in the inhibition of neurodegenerative diseases progression. It is the main metabolite of the complex polyphenolic compounds and is believed to be responsible for beneficial effects associated with consumption of the food products rich in polyphenols. Protocatechuic acid is present in the circulation significantly longer and at higher concentrations than parent compounds and easily crosses the blood brain barrier. The aim of the following paper is to provide an extensive and actual report on protocatechuic acid and its pharmacological potential in prevention and/or treatment of neurodegenerative diseases in humans based on existing data from both in vitro and in vivo studies. Experimental studies strongly support the role of protocatechuic acid in the prevention of neurodegenerative processes, including Alzheimer's and Parkinson's diseases, due to its favorable influence on processes underlying cognitive and behavioral impairment, namely accumulation of the β-amyloid plaques in brain tissues, hyperphosphorylation of tau protein in neurons, excessive formation of reactive oxygen species and neuroinflammation. There is a growing evidence that protocatechuic acid may become in the future efficacious and safe substance that protects against neurodegenerative disorders.

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Passiflora incarnata L. has been used as a medicinal plant in South America and Europe since the 16th century. Previous pharmacological studies focused mainly on the plant's sedative, anxiolytic, and anticonvulsant effects on the central nervous system and its supporting role in the treatment of addiction. The aim of the present study was to evaluate the behavioral and neurochemical effects of long-term oral administration of P. incarnata. The passionflower extract (30, 100, or 300 mg/kg body weight/day) was given to 4-week-old male Wistar rats via their drinking water. Tests were conducted after 7 weeks of treatment. Spatial memory was assessed in a water maze, and the levels of amino acids, monoamines, and their metabolites were evaluated in select brain regions by high performance liquid chromatography (HPLC). We observed reduced anxiety and dose-dependent improvement of memory in rats given passionflower compared to the control group. In addition, hippocampal glutamic acid and cortical serotonin content were depleted, with increased levels of metabolites and increased turnover. Thus, our results partially confirmed the proposed mechanism of action of P. incarnata involving GABAA receptors. Copyright © 2016 John Wiley & Sons, Ltd.