Acute Striato-Cortical Synchronization Induces Focal Motor Seizures in Primates

Objective: Whether the basal ganglia are involved in the cortical synchronization during focal seizures is still an open question. In the present study, we proposed to synchronize cortico-striatal activities acutely inducing striatal disinhibition, performing GABA-antagonist injections within the putamen in primates. Method: Experiments were performed on three fascicularis monkeys. During each experimental session, low volumes of bicuculline (0.5–4 μL) were injected at a slow rate of 1 μL/min. Spontaneous behavioral changes were classified according to Racine’s scale modified for primates. These induced motor behaviors were correlated with electromyographic, electroencephalographic, and putaminal and pallidal local field potentials changes in activity. Results: acute striatal desinhibition induced focal motor seizures. Seizures were closely linked to cortical epileptic activity synchronized with a striatal paroxysmal activity. These changes in striatal activity preceded the cortical epileptic activity and the induced myoclonia, and both cortical and subcortical activities were coherently synchronized during generalized seizures. Interpretation: Our results strongly suggest the role of the sensorimotor striatum in the regulation and synchronization of cortical excitability. These dramatic changes in the activity of this “gating” pathway might influence seizure susceptibility by modulating the threshold for the initiation of focal motor seizures.

0427 Bicuculine Increased the Cataplexy in the Male Taiep Rats: An Animal Model of Narcolepsy with an Inherent Tubulopathy

Introduction Narcolepsy is a hypersomnolence that is characterized by sleep fragmentation, sleep paralysis, hypnagogic hallucinations and cataplexy that is characterized by atonia induced by strong emotions. The amygdala is the trigger for cataplexy through GABAergic mechanisms. Taiep is a myelin mutant with TUBB4A tubulopathy which showed spontaneous episodes of atonia or induced by manipulations from the tail or the thorax. EEG recordings during immobility episodes (IE′s) had a cerebral cortex desynchronized associated to theta rhythm in the hippocampus. The aim of this sturdy was to analyze the effects of bicuculine administration on IE′s and sleep-wake pattern on adult male taiep rats. Methods We used 6 taiep male rats at 9 months of age. The subjects (Ss) lived in individual acrylic cages with water and food pellets available ad libitum, under a 12:12 light-dark cycle (lights on at 0700), with controlled temperature and humidity recording room. All Ss were implanted to record EEG, EMG and EOG to characterize EI′s. We evaluated a basal 24 h EEG recording and then after bicuculine i.p. administration of 0.5, 1 y 1.5 mg/Kg every 48h. We measured the number, mean duration and latency to the first IE′s. Results The duration of IE′s increased 527% with 1 mg/Kg and reach 700% with 1.5 mg/Kg of bicuculine (P<0.01) with respect to saline-treated control group. Importantly, the frequency of IEs did not differ among the groups and did not affect the number of awake, slow wave or rapid eye movements sleep phases. Conclusion Bicuculine, a specific GABA antagonist, modify the duration of IES but not their frequency supporting a role of GABAergic mechanism on IE′s. It is relevant because sodium oxybate, an indirect GABA agonist, reduced cataplexy and improved sleep quality on narcoleptic patients. Support CONACYT grants 243333 and 243247 to CC and JRE, respectively and from VIEP-BUAP 2019 to CA in Neuroendocrinología BUAP-CA-288.

Dopamine D2 receptors in striatal output neurons enable the psychomotor effects of cocaine

The psychomotor effects of cocaine are mediated by dopamine (DA) through stimulation of striatal circuits. Gabaergic striatal medium spiny neurons (MSNs) are the only output of this pivotal structure in the control of movements. The majority of MSNs express either the DA D1 or D2 receptors (D1R, D2R). Studies have shown that the motor effect of cocaine depends on the DA-mediated stimulation of D1R-expressing MSNs (dMSNs), which is mirrored at the cellular level by stimulation of signaling pathways leading to phosphorylation of ERKs and induction of c-fos. Nevertheless, activation of dMSNs by cocaine is necessary but not sufficient, and D2R signaling is required for the behavioral and cellular effects of cocaine. Indeed, cocaine motor effects and activation of signaling in dMSNs are blunted in mice with the constitutive knockout of D2R (D2RKO). Using mouse lines with a cell-specific knockout of D2R either in MSNs (MSN-D2RKO) or in dopaminergic neurons (DA-D2RKO), we show that D2R signaling in MSNs is required and permissive for the motor stimulant effects of cocaine and the activation of signaling in dMSNs. MSN-D2RKO mice show the same phenotype as constitutive D2RKO mice both at the behavioral and cellular levels. Importantly, activation of signaling in dMSNs by cocaine is rescued by intrastriatal injection of the GABA antagonist, bicuculline. These results are in support of intrastriatal connections of D2R+-MSNs (iMSNs) with dMSNs and indicate that D2R signaling in MSNs is critical for the function of intrastriatal circuits.

Acidification and γ -aminobutyric acid independently alter kairomone-induced behaviour

Exposure to high p CO 2 or low pH alters sensation and behaviour in many marine animals. We show that crab larvae lose their ability to detect and/or process predator kairomones after exposure to low pH over a time scale relevant to diel pH cycles in coastal environments. Previous work suggests that acidification affects sensation and behaviour through altered neural function, specifically the action of γ -aminobutyric acid (GABA), because a GABA antagonist, gabazine, restores the original behaviour. Here, however, gabazine resulted in a loss of kairomone detection/processing, regardless of pH. Our results also suggest that GABAergic signalling is necessary for kairomone identification in these larvae. Hence, the mechanism for the observed pH effect varies from the original GABA hypothesis. Furthermore, we suggest that this pH effect is adaptive under diel-cycling pH.

Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels

Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO 2 ) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO 2 levels (961 µatm) impair this escape behaviour during a predator–prey interaction. Elevated-CO 2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO 2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO 2 , as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO 2 levels could have potentially far-reaching implications for marine ecosystems.

Mikania glomerata: Phytochemical, Pharmacological, and Neurochemical Study

The present study primarily aims to identify the relative density and the fatty acids (methyl esters) content present in the standardized ethanol extract of leaves ofM. glomerata(EPMG). Meanwhile, in a second moment, this study evaluated the effects of the EPMG on the levels of amino acids in the hippocampus, and the mechanism of sedative and anxiolytic action. Adult mice were treated with doses of 200, 300, and 400 mg/kg and evaluated in open field, elevated plus-maze, light dark, and rotarod tests. Moreover, in the behavioral tests diazepam (GABAergic anxiolytic, 2 mg/kg) as positive control and flumazenil (GABA antagonist, 2.5 mg/kg) were used to identify mechanism of sedative and anxiolytic action produced by EPMG. The EPMG is constituted by the following compounds: methyl cinnamate, 2H-1-benzopyran-2-one, (2-hydroxyphenyl)methyl propionate, (Z)-methyl-hexadec-7-enoate, methyl hexadecanoate, hexadecanoic acid, (Z)-methyl-octadec-9-enoate, octadecanoic acid, and squalene. This extract demonstrated anxiolytic effects, which may be mediated by GABAergic system, and was able to increase GABA levels and reduce of glutamate and aspartate concentrations in mice hippocampus, which can directly and/or indirectly assist in their anxiolytic effect. Although more studies are needed, the EPMG could represent an interesting therapeutical strategy in the treatment of anxiety.