High sucrose diet does not impact spatial cognition in rats using advanced touchscreen technology.

INTRODUCTION: Western diets, including those consisting of saturated fats, simple sugars and processed foods, is rising at an unprecedented rate. These lead to obesity and metabolic diseases, and possibly cognitive deficits. Exploring this, recent studies demonstrate marked impairment in spatial learning in rodents exposed to high-sugar diets. We utilised advanced touchscreen technology to assess several spatial and non-spatial components of cognition in rats chronically exposed to a high sucrose diet. METHODS: Male Wistar rats received 70 ml of 10% sucrose solution each day, or control tap water, persisting for the experiment duration (total n = 32). After 5 weeks of diet, rats performed Pairwise Discrimination, Location Discrimination, or Progressive Ratio tasks on automated touchscreens, and performance compared between groups. RESULTS: Sucrose rats consumed all the sugar solution provided to them, and had significantly increased caloric intake, compared to controls (p < 0.0001). However, in all tests, we found no significant difference in cognitive performance between Sucrose and Control treated rats. This included the number of trials for acquisition, and reversal, in Pairwise Discrimination, and number of trials required to complete Location Discrimination (p > 0.05 for all outcomes). No differences were observed in perseverative behaviour, motivation levels, or processing speed. CONCLUSION: Our study found no evidence to suggest that chronic consumption of sucrose impairs cognition, including both spatial and non-spatial learning tasks. These findings suggest that not all aspects of spatial cognition are negatively impacted by high sugar diet in rodents, and that particular use of touchscreen technology may probe different aspects of cognition than traditional tasks.

Altered cardiac structure and function is related to seizure frequency in a rat model of chronic acquired temporal lobe epilepsy.

OBJECTIVE: This study aimed to prospectively examine cardiac structure and function in the kainic acid-induced post-status epilepticus (post-KA SE) model of chronic acquired temporal lobe epilepsy (TLE), specifically to examine for changes between the pre-epileptic, early epileptogenesis and the chronic epilepsy stages. We also aimed to examine whether any changes related to the seizure frequency in individual animals. METHODS: Four hours of SE was induced in 9 male Wistar rats at 10 weeks of age, with 8 saline treated matched control rats. Echocardiography was performed prior to the induction of SE, two- and 10-weeks post-SE. Two weeks of continuous video-EEG and simultaneous ECG recordings were acquired for two weeks from 11 weeks post-KA SE. The video-EEG recordings were analyzed blindly to quantify the number and severity of spontaneous seizures, and the ECG recordings analyzed for measures of heart rate variability (HRV). PicroSirius red histology was performed to assess cardiac fibrosis, and intracellular Ca2+ levels and cell contractility were measured by microfluorimetry. RESULTS: All 9 post-KA SE rats were demonstrated to have spontaneous recurrent seizures on the two-week video-EEG recording acquired from 11 weeks SE (seizure frequency ranging from 0.3 to 10.6 seizures/day with the seizure durations from 11 to 62 s), and none of the 8 control rats. Left ventricular wall thickness was thinner, left ventricular internal dimension was shorter, and ejection fraction was significantly decreased in chronically epileptic rats, and was negatively correlated to seizure frequency in individual rats. Diastolic dysfunction was evident in chronically epileptic rats by a decrease in mitral valve deceleration time and an increase in E/E` ratio. Measures of HRV were reduced in the chronically epileptic rats, indicating abnormalities of cardiac autonomic function. Cardiac fibrosis was significantly increased in epileptic rats, positively correlated to seizure frequency, and negatively correlated to ejection fraction. The cardiac fibrosis was not a consequence of direct effect of KA toxicity, as it was not seen in the 6/10 rats from separate cohort that received similar doses of KA but did not go into SE. Cardiomyocyte length, width, volume, and rate of cell lengthening and shortening were significantly reduced in epileptic rats. SIGNIFICANCE: The results from this study demonstrate that chronic epilepsy in the post-KA SE rat model of TLE is associated with a progressive deterioration in cardiac structure and function, with a restrictive cardiomyopathy associated with myocardial fibrosis. Positive correlations between seizure frequency and the severity of the cardiac changes were identified. These results provide new insights into the pathophysiology of cardiac disease in chronic epilepsy, and may have relevance for the heterogeneous mechanisms that place these people at risk of sudden unexplained death.

New insights in the mode of action of (+)-erythravine and (+)-11α-hydroxy-erythravine alkaloids.

Erythrinian alkaloids ((+)-erythravine and (+)-11-α-hydroxy-erythravine) have been pointed as the main responsible agents for the anticonvulsant and anxiolytic properties of Erythrina mulungu Mart ex Benth. The present work provides a new set of information about the mode of action of these alkaloids by the use of a complementary approach of neurochemical and electrophysiological assays. We propose here that the antiepileptic and anxiolytic properties exhibited by both alkaloids appear not to be related to the inhibition of glutamate binding or GABA uptake, or even to the increase of glutamate uptake or GABA binding, as investigated here by the use of rat cortical synaptosomes. Similarly, and even in a high concentration, (+)-erythravine and (+)-11-α-hydroxy-erythravine did not modulate the main sodium and potassium channel isoforms checked by the use of voltage-clamp studies on Xenopus laevis oocytes. However, unlike (+)-11-α-hydroxy-erythravine, which presented a little effect, it was possible to observe that the (+)-erythravine alkaloid produced a significant inhibitory modulation on α4ß2, α4ß4 and α7 isoforms of nicotinic acetylcholine receptors also checked by the use of voltage-clamp studies, which could explain at least partially its anxiolytic and anticonvulsant properties. Since (+)-11-α-hydroxy-erythravine and (+)-erythravine modulated nicotinic acetylcholine receptors to different extents, it is possible to reinforce that small differences between the chemical structure of these alkaloids can affect the selectivity and affinity of target-ligand interactions, conferring distinct potency and/or pharmacological properties to them, as previously suggested by differential experimental comparison between different erythrinian alkaloids.

Anxiolytic-like effect of a novel peptide isolated from the venom of the social wasp Synoeca surinama.

Pathological anxiety is among the most common psychiatric illnesses, but current treatment is highly limited. In this study, we investigated the potential anxiolytic-like effects of a peptide isolated from Synoeca surinama venom. Rats treated with this peptide spent more time exploring the open arms of elevated plus maze, which indicates an anxiolytic-like profile for this peptide. This study is the first to show the pharmacological use of S. surinama venom in the treatment of anxiety.