Food for thought: honeybee foraging, memory, and acetylcholine

Anxiolytic, Promnesic, Anti-Acetylcholinesterase and Antioxidant Effects of Cotinine and 6-Hydroxy-L-Nicotine in Scopolamine-Induced Zebrafish (Danio rerio) Model of Alzheimer's Disease

Cotinine (COT) and 6-hydroxy-L-nicotine (6HLN) are two nicotinic derivatives that possess cognitive-improving abilities and antioxidant properties in different rodent models of Alzheimer's disease (AD), eluding the side-effects of nicotine (NIC), the parent molecule. In the current study, we evaluated the impact of COT and 6HLN on memory deterioration, anxiety, and oxidative stress in the scopolamine (SCOP)-induced zebrafish model of AD. For this, COT and 6HLN were acutely administered by immersion to zebrafish that were treated with SCOP before testing. The memory performances were assessed in Y-maze and object discrimination (NOR) tasks, while the anxiety-like behavior was evaluated in the novel tank diving test (NTT). The acetylcholinesterase (AChE) activity and oxidative stress were measured from brain samples. The RT-qPCR analysis was used to evaluate the npy, egr1, bdnf, and nrf2a gene expression. Our data indicated that both COT and 6HLN attenuated the SCOP-induced anxiety-like behavior and memory impairment and reduced the oxidative stress and AChE activity in the brain of zebrafish. Finally, RT-qPCR analysis indicated that COT and 6HLN increased the npy, egr1, bdnf, and nrf2a gene expression. Therefore, COT and 6HLN could be used as tools for improving AD conditions.

Novel Microbial Sources of Tropane Alkaloids: First Report of Production by Endophytic Fungi Isolated from Datura metel L

Eighteen endophytic fungi were isolated from various tissues of Datura metel and genes encoding for putrescine N-methyltransferase (PMT), tropinone reductase 1 (TR1) and hyoscyamine 6β-hydroxylase (H6H) were used as molecular markers for PCR-based screening approach for tropane alkaloids (TAs) producing endophytic fungi. These fungi were identified taxonomically by sequence analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) and also based on morphological characteristics of the fungal spore as Colletotrichum boninense, Phomopsis sp., Fusarium solani, Colletotrichum incarnatum, Colletotrichum siamense and Colletotrichum gloeosporioides. The production of TAs hyoscyamine and scopolamine by the fungi has been ascertained using chromatography and spectroscopy methods by comparison with the standards. Among the fungi, the highest yields of hyoscyamine (3.9 mg/L) and scopolamine (4.1 mg/L) were found in C. incarnatum culture. This is the first report of endophytic fungi possess the PMT, TR1 and H6H genes and produces TAs. These endophytic fungi have significant potential to be applied in fermentation technology to meet the demands for TAs economically.

Neural correlates of expression-independent memories in the crab Neohelice

The neural correlates of memory have been usually examined considering that memory retrieval and memory expression are interchangeable concepts. However, our studies in the crab Neohelice (Chasmagnathus) granulata and in other memory models have shown that memory expression is not necessary for memory to be re-activated and become labile. In order to examine putative neural correlates of memory in the crab Neohelice, we contrast changes induced by training in both animal's behavior and neuronal responses in the medulla terminalis using in vivo Ca(2+) imaging. Disruption of long-term memory by the amnesic agents MK-801 or scopolamine (5μg/g) blocks the learning-induced changes in the Ca(2+) responses in the medulla terminalis. Conversely, treatments that lead to an unexpressed but persistent memory (weak training protocol or scopolamine 0.1μg/g) do not block these learning-induced neural changes. The present results reveal a set of changes in the neural activity induced by training that correlates with memory persistence but not with the probability of this memory to be expressed in the long-term. In addition, the study constitutes the first in vivo evidence in favor of a role of the medulla terminalis in learning and memory in crustaceans, and provides a physiological evidence indicating that memory persistence and the probability of memory to be expressed might involve separate components of memory traces.

Memory beyond expression

The idea that memories are not invariable after the consolidation process has led to new perspectives about several mnemonic processes. In this framework, we review our studies on the modulation of memory expression during reconsolidation. We propose that during both memory consolidation and reconsolidation, neuromodulators can determine the probability of the memory trace to guide behavior, i.e. they can either increase or decrease its behavioral expressibility without affecting the potential of persistent memories to be activated and become labile. Our hypothesis is based on the findings that positive modulation of memory expression during reconsolidation occurs even if memories are behaviorally unexpressed. This review discusses the original approach taken in the studies of the crab Neohelice (Chasmagnathus) granulata, which was then successfully applied to test the hypothesis in rodent fear memory. Data presented offers a new way of thinking about both weak trainings and experimental amnesia: memory retrieval can be dissociated from memory expression. Furthermore, the strategy presented here allowed us to show in human declarative memory that the periods in which long-term memory can be activated and become labile during reconsolidation exceeds the periods in which that memory is expressed, providing direct evidence that conscious access to memory is not needed for reconsolidation. Specific controls based on the constraints of reminders to trigger reconsolidation allow us to distinguish between obliterated and unexpressed but activated long-term memories after amnesic treatments, weak trainings and forgetting. In the hypothesis discussed, memory expressibility--the outcome of experience-dependent changes in the potential to behave--is considered as a flexible and modulable attribute of long-term memories. Expression seems to be just one of the possible fates of re-activated memories.

Quercetin protects against chronic aluminum-induced oxidative stress and ensuing biochemical, cholinergic, and neurobehavioral impairments in rats

In this study, we investigated the protective effect of chronic quercetin (a natural flavanoid) administration against Al-induced cognitive impairments, oxidative damage, and cholinergic dysfunction in male Wistar rats. Al lactate (10 mg/kg b.wt./day) was administered intragastrically to rats which were pre-treated with quercetin (10 mg/kg b.wt./day, intragastrically) for 12 weeks. At the end of 6 or 12 weeks of the study, several behavioral parameters were carried out to evaluate cognitive functions. Further after 12 weeks of exposure, various biochemical tests and H&E staining were performed to assess the extent of oxidative damage and neurodegeneration, respectively. Al levels were also estimated in HC and CS regions of rat brain. Chronic administration of quercetin caused significant improvement in the muscle coordination, cognition, anxiety, locomotion, and initial exploratory patterns in Al-treated rats. Quercetin supplementation to Al-treated animals also reduced oxidative stress, decreased ROS production, increased MnSOD activity and glutathione levels with decreased lipid peroxidation and protein oxidation. It increased AChE activity and ATP levels in HC and CS regions of rat brain compared to Al-treated rats. Quercetin administration ameliorates Al-induced neurodegenerative changes in Al-treated rats as seen by H&E staining. Further with the help of atomic absorption spectrophotometer, we found that quercetin supplementation to Al-treated rats also decreases the accumulation of Al in the HC and CS regions of rat brain. Taken together the results of this study show that quercetin offers neuroprotection against Al-induced cognitive impairments, cholinergic dysfunction, and associated oxidative damage in rats.

A genome-wide inventory of neurohormone GPCRs in the red flour beetle Tribolium castaneum

Insect neurohormones (biogenic amines, neuropeptides, and protein hormones) and their G protein-coupled receptors (GPCRs) play a central role in the control of behavior, reproduction, development, feeding and many other physiological processes. The recent completion of several insect genome projects has enabled us to obtain a complete inventory of neurohormone GPCRs in these insects and, by a comparative genomics approach, to analyze the evolution of these proteins. The red flour beetle Tribolium castaneum is the latest addition to the list of insects with a sequenced genome and the first coleopteran (beetle) to be sequenced. Coleoptera is the largest insect order and about 30% of all animal species living on earth are coleopterans. Some coleopterans are severe agricultural pests, which is also true for T. castaneum, a global pest for stored grain and other dried commodities for human consumption. In addition, T. castaneum is a model for insect development. Here, we have investigated the presence of neurohormone GPCRs in Tribolium and compared them with those from the fruit fly Drosophila melanogaster (Diptera) and the honey bee Apis mellifera (Hymenoptera). We found 20 biogenic amine GPCRs in Tribolium (21 in Drosophila; 19 in the honey bee), 48 neuropeptide GPCRs (45 in Drosophila; 35 in the honey bee), and 4 protein hormone GPCRs (4 in Drosophila; 2 in the honey bee). Furthermore, we identified the likely ligands for 45 of these 72 Tribolium GPCRs. A highly interesting finding in Tribolium was the occurrence of a vasopressin GPCR and a vasopressin peptide. So far, the vasopressin/GPCR couple has not been detected in any other insect with a sequenced genome (D. melanogaster and six other Drosophila species, Anopheles gambiae, Aedes aegypti, Bombyx mori, and A. mellifera). Tribolium lives in very dry environments. Vasopressin in mammals is the major neurohormone steering water reabsorption in the kidneys. Its presence in Tribolium, therefore, might be related to the animal's need to effectively control water reabsorption. Other striking differences between Tribolium and the other two insects are the absence of the allatostatin-A, kinin, and corazonin neuropeptide/receptor couples and the duplications of other hormonal systems. Our survey of 340 million years of insect neurohormone GPCR evolution shows that neuropeptide/receptor couples can easily duplicate or disappear during insect evolution. It also shows that Drosophila is not a good representative of all insects, because several of the hormonal systems that we now find in Tribolium do not exist in Drosophila.