Environmental cues associated with morphine modulate release of glutamate and γ-aminobutyric acid in ventral subiculum

Objective To investigate whether environmental cues associated with different properties of morphine could regulate the extracellular levels of glutamate and y-aminobutyric acid （GABA） in the hippocampal ventral subiculum, which play a critical role in the reinstatement of drug-seeking behavior induced by environmental cues. Methods Conditioning place preference （CPP） and conditioning place aversion （CPA） models were used to establish environment associated with rewarding and aversive properties of morphine respectively. Microdialysis and high performance liquid chromatography were used to measure the extracelluar level of glutamate and GABA in the ventral subiculum under these environmental cues. Results Exposure to the environmental cues associated with rewarding properties of morphine resulted in a decrease （approximately 11%） of extracellular level of GABA in ventral subiculum, and exposure to the environmental cues associated with aversive properties of morphine resulted in an increase （approximately 230%） of extracellular level of glutamate in ventral subiculum. Conclusion Environmental cues associated with different properties of morphine modulate the release of distinct neurotransmitters in the hippocampal ventral subiculum possibly through different neural circuit.

B Vitamins Supplementation Can Improve Cognitive Functions and May Relate to the Enhancement of Transketolase Activity in A Rat Model of Cognitive Impairment Associated with High-fat Diets

Objective:To determine whether B vitamin treatment was sufficient to reduce cognitive impairment associated with high-fat diets in rats and to modulate transketolase(TK)expression and activity.Methods:To test this,we separated 50 rats into five groups that were either fed a standard chow diet(controls)or a high-fat diet(experimental groups HO,HI,H2,and H3).HO group animals received no additional dietary supplementation,while H1 group animals were administered 100 mg/kg body weight(BW)thiamine,100 mg/kg BW riboflavin,and 250 mg/kg BW niacin each day,and group H2 animals received daily doses of 100 mg/kg BW pyridoxine,100 mg/kg BW cobalamin,and 5 mg/kg BW folate.Animals in the H3 group received the B vitamin regimens administered to both H1 and H2 each day.Results:Over time,group HO exhibited greater increases in BW and fat mass relative to other groups.When spatial and memory capabilities in these animals were evaluated via conditioned taste aversion(CTA)and Morris Water Maze(MWM),we found B vitamin treatment was associated with significant improvements relative to untreated HO controls.Similarly,B vitamin supplementation was associated with elevated TK expression in erythrocytes and hypothalamus of treated animals relative to those in HO(P<0.05).Conclusion:Together,these findings suggest B vitamin can modulate hypothalamic TK activity to reduce the severity of cognitive deficits in a rat model of obesity.As such,B vitamin supplementation may be a beneficial method for reducing cognitive dysfunction in clinical settings associated with high-fat diets.

The differential requirement of mushroom body α/β subdivisions in long-term memory retrieval in Drosophila

The mushroom body(MB),a bilateral brain structure pos-sessing about 2000-2500 neurons per hemisphere,plays a central role in olfactory learning and memory in Dros-ophila melanogaster.Extensive studies have demonstrat-ed that three major types of MB neurons(α/β,α’/β’andγ)exhibit distinct functions in memory processing,including the critical role of approximately 1000 MBα/βneurons in retrieving long-term memory.Inspired by recent fi ndings that MBα/βneurons can be further divided into three subdivisions(surface,posterior and core)and wherein theα/βcore neurons play an permissive role in long-term memory consolidation,we examined the functional differ-ences of all the three morphological subdivisions of MBα/βby temporally precise manipulation of their synaptic outputs during long-term memory retrieval.We found the normal neurotransmission from a combination of MBα/βsurface and posterior neurons is necessary for retrieving both aversive and appetitive long-term memory,whereas output from MBα/βposterior or core subdivision alone is dispensable.These results imply a specifi c requirement of about 500 MBα/βneurons in supporting long-term memory retrieval and a further functional partitioning for memory processing within the MBα/βregion.

Eliciting conditioned taste aversion in lizards:Live toxic prey are more effective than scent and taste cues alone

Conditioned taste aversion(CTA)is an adaptive learning mechanism whereby a consumer associates the taste of a certain food with symptoms caused by a toxic substance,and thereafter avoids eating that type of food.Recently,wildlife researchers have employed CTA to discourage native fauna from ingesting toxic cane toads(Rhinella marina),a species that is invading tropical Australia.In this paper,we compare the results of 2 sets of CTA trials on large varanid lizards(“goannas,”Varanus panoptes).One set of trials(described in this paper)exposed recently-captured lizards to sausages made from cane toad flesh,laced with a nausea-inducing chemical(lithium chloride)to reinforce the aversion response.The other trials(in a recently-published paper,reviewed herein)exposed free-ranging lizards to live juvenile cane toads.The effectiveness of the training was judged by how long a lizard survived in the wild before it was killed(fatally poisoned)by a cane toad.Both stimuli elicited rapid aversion to live toads,but the CTA response did not enhance survival rates of the sausage-trained goannas after they were released into the wild.In contrast,the goannas exposed to live juvenile toads exhibited higher long-term survival rates than did untrained conspecifics.Our results suggest that although it is relatively easy to elicit short-term aversion to toad cues in goannas,a biologically realistic stimulus(live toads,encountered by free-ranging predators)is most effective at buffering these reptiles from the impact of invasive toxic prey.

The Anterior Insula and its Projection to the Prelimbic Cortex are Involved in the Regulation of 5-HT-Induced Itch

Itch is an unpleasant sensation that urges people and animals to scratch.Neuroimaging studies on itch have yielded extensive correlations with diverse cortical and subcortical regions,including the insular lobe.However,the role and functional specificity of the insular cortex(IC)and its subdivisions in itch mediation remains unclear.Here,we demonstrated by immunohistochemistry and fiber photometry tests,that neurons in both the anterior insular cortex(AIC)and the posterior insular cortex(PIC)are activated during acute itch processes.Pharmacogenetic experiments revealed that nonselective inhibition of global AIC neurons,or selective inhibition of the activity of glutaminergic neurons in the AIC,reduced the scratching behaviors induced by intradermal injection of 5-hydroxytryptamine(5-HT),but not those induced by compound 48/80.However,both nonselective inhibition of global PIC neurons and selective inhibition of glutaminergic neurons in the PIC failed to affect the itching-scratching behaviors induced by either 5-HT or compound 48/80.In addition,pharmacogenetic inhibition of AIC glutaminergic neurons effectively blocked itch-associated conditioned place aversion behavior,and inhibition of AIC glutaminergic neurons projecting to the prelimbic cortex significantly suppressed 5-HT-evoked scratching.These findings provide preliminary evidence that the AIC is involved,at least partially via aversive emotion mediation,in the regulation of 5-HT-,but not compound 48/80-induced itch.