Seizure control by decanoic acid through direct AMPA receptor inhibition

The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet

Simultaneously Hermaphroditic Shrimp Use Lipophilic Cuticular Hydrocarbons as Contact Sex Pheromones

Successful mating is essentially a consequence of making the right choices at the correct time. Animals use specific strategies to gain information about a potential mate, which is then applied to decision-making processes. Amongst the many informative signals, odor cues such as sex pheromones play important ecological roles in coordinating mating behavior, enabling mate and kin recognition, qualifying mate choice, and preventing gene exchange among individuals from different populations and species. Despite overwhelming behavioral evidence, the chemical identity of most cues used in aquatic organisms remains unknown and their impact and omnipresence have not been fully recognized. In many crustaceans, including lobsters and shrimps, reproduction happens through a cascade of events ranging from initial attraction to formation of a mating pair eventually leading to mating. We examined the hypothesis that contact pheromones on the female body surface of the hermaphroditic shrimp Lysmata boggessi are of lipophilic nature, and resemble insect cuticular hydrocarbon contact cues. Via chemical analyses and behavioural assays, we show that newly molted euhermaphrodite-phase shrimp contain a bouquet of odor compounds. Of these, (Z)-9-octadecenamide is the key odor with hexadecanamide and methyl linoleate enhancing the bioactivity of the pheromone blend. Our results show that in aquatic systems lipophilic, cuticular hydrocarbon contact sex pheromones exist; this raises questions on how hydrocarbon contact signals evolved and how widespread these are in the marine environment

A pheromone bouquet controls the reproductive behaviour of the male shore crab, Carcinus maenas

The reproduction of many brachyuran crustaceans involves the formation of mating pairs often around the time of the female moult with attraction of a sexual partner and mating behaviour controlled by sex pheromones. In shore crabs, Carcinus maenas, females produce sex pheromones that are released in the urine. High Performance Liquid Chromatography analysis (HPLC) of female urine shows that the pheromone, identified as the nucleotide uridine diphosphate (UDP), elutes as an unresolved peak with structurally related nucleotides. We examined female urine samples over the moult cycle and detected UDP as well as uridine triphosphate (UTP). Bioassays were conducted to establish the possibility of a blend of nucleotides forming a sex pheromone bouquet in C. maenas. Whilst UDP induced the male mate guarding behaviour (cradling), a mixture of the two nucleotides at a ratio of 4:1 UDP:UTP elicited an even stronger mating response than either UDP or UTP individually. The urine concentration and composition of these nucleotides changes over the moult period pre and post ecdysis, providing evidence that a pheromone bouquet composition is not always constant. The change of the bouquet is related to the physiological state of the sender, here the moult cycle. Our study unravels the functionality of reaction-specific molecules in a pheromone bouquet. Whilst UDP is the mating signal, UTP acts as an attractant and combined they maximise the reproductive response. The use of bouquets provides species-specificity, potentially enabling reproductive isolation of sympatric species, and contains valuable information on the physiological state of the sender

Number of MP shrimp (out of 30) displaying grasping and touching behavior toward tubes treated with cuticular extracts (hexane) of newly molted euhermaphrodite-phase (EP), newly molted male-phase (MP) shrimp, and components of newly molted EP extract, including (Z)-9-octadecenamide, a blend of (Z)-9-octadecenamide and squalene (blend 1), and a blend of (Z)-9-octadecenamide and methyl linoleate (blend 2).

<p>*: Number of MP shrimp displaying touching and grasping in the newly molted EP, (Z)-9-octadecenamide, and blend treatments is significantly higher (<i>P</i><0.01) than in the newly molted MP shrimp and the control).</p

Gas chromatograms of hexane extracts of newly molted euhermaphrodite phase (EP) shrimp (top) and intermolt EP shrimp, newly molted male phase (MP) shrimp, and intermolt MP shrimp (bottom, because there are no differences between the chromatograms of the latter three samples only the newly molted MP's chromatogram is presented here).

<p>Peak 1 (pentadecyl 2-propenoate) at t = 7.44 min, peak 2 (unidentified) at t = 10.26 min, peak 3 (unidentified) at t = 10.74 min, peak 4 ((Z)-9-octadecenamide) at t = 13.81 min, peak 5 (squalene) at t = 17.32 min, peak 6 (dodecyl octadecanoate) at t = 21.30 min, peak 7 (unresolved organic acid ester) at t = 28.06 min, peak 8 (unidentified, unresolved double peak) at t = 28.16 min.</p

Gas chromatograms of ethanol extracts of newly molted euhermaphrodite phase (EP) shrimp and intermolt EP shrimp, newly molted male phase (MP) shrimp, and intermolt MP shrimp.

<p>A: represents the chromatograms of intermolt EP shrimp, newly molted MP shrimp and intermolt MP shrimp; B: enlargement showing detail of minor components in chromatograms of newly molted MP shrimp and intermolt MP shrimp; C: enlargement showing detail of minor components in chromatograms of intermolt EP shrimp; D: chromatograms of newly molted EP shrimp. Peak 1 (ethyl palmitate) at t = 10.43 min, peak 2 (methyl linoleate) at t = 12.05 min, peak 3 (hexadecanamide) at t = 12.10 min, peak 4 (ethyl stearate) at t = 12.25 min, peak 5 (methyl eicosapentaenoate) at t = 12.50 min, peak 6 (methyl eicopentaenoate) at t = 13.48 min, peak 7 ((Z)-9-octadecenamide) at t = 13.73 min, peak 8 (methyl or ethyl docohexanoate) at t = 14.98 min, peak 9 (squalene) at t = 17.27 min, peak 10 (unidentified) at t = 20.15 min.</p

Identification of a female sex pheromone in Carcinus maenas

Despite major progress in our understanding of animal signaling systems, the identification of chemical signals in aquatic organisms is still in its infancy. Exemplary for this is the lack of structural knowledge of crustacean sex pheromones despite their initial description in crabs almost 40 yr ago. We hypothesized that species in which the reproductive event is linked to a short window of mating opportunities centered around the time of ecdysis would be ideal to purify and identify such a cue. Here we present the first identification of a crustacean sex pheromone, the female signal produced by the green crab Carcinus maenas from both conditioned seawater and female urine. We used a bioassay-driven purification scheme combined with a candidate approach focusing on excreted compounds that changed through the course of the female molt cycle. Uridine diphosphate (UDP), a nucleotide accumulated from UDP-N-acetylglucosamine during chitin biosynthesis, is the major component of the female crab pheromone and induced all key characteristics of male sexual behavior in bioassays (i.e. pre- and post-copulatory guarding of the female and initiation of mating) at a threshold of 10(-5) M UDP in seawater. The identification of a nucleotide pheromone in crustaceans will enable future studies on signal specificity, biological function, biosynthesis, reception, and evolution as well as focus its potential use in pest control and aquaculture, thus allowing for a major expansion of crustacean chemical and behavioral ecology research that was hindered by the lack of structural knowledge