The Role of Beta-Endorphin in Cocaine-Induced Conditioned Place Preference, Its Extinction, and Reinstatement in Male and Female Mice

Endogenous opioids have been implicated in cocaine reward. However, the role of each opioid peptide in this regard is unknown. Notably, the role of each peptide in extinction and reinstatement is not fully characterized. Thus, we assessed whether cocaine-induced conditioned place preference (CPP) and its extinction and reinstatement would be altered in the absence of beta-endorphin. We also examined if sex-related differences would exist in these processes. Male and female mice lacking beta-endorphin and their respective controls were tested for baseline place preference on day 1. On day 2, mice were treated with saline/cocaine (15 mg/kg) and confined to the vehicle- or drug-paired chamber for 30 min, respectively. In the afternoon, mice were treated with the alternate treatment and confined to the opposite chamber. Mice were then tested for CPP on day 3. Mice then received additional conditioning on this day as well as on day 4. Mice were then tested for CPP on day 5. Mice then received extinction training on day 9. On day 10, mice were tested for extinction and then reinstatement of CPP following a priming dose of cocaine (7.5 mg/kg). Male and female mice lacking beta-endorphin did not exhibit CPP following single conditioning with cocaine. On the other hand, only male mice lacking beta-endorphin failed to show CPP after repeated conditioning. Nonetheless, reinstatement of CPP was blunted in both male and female mice lacking beta-endorphin compared to controls. The present results suggest that beta-endorphin plays a functional role in cocaine-induced CPP and its reinstatement, and sex-related differences exist in the regulatory action of beta-endorphin on the acquisition but not reinstatement of cocaine CPP.

Insights into electrophysiological mechanisms of atrial fibrillation propagation using simultaneous bi-atrial mapping

Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Oxford Biomedical Research Centre Introduction Early evidence of pulmonary vein triggers initiating AF has led to focus on the left atrium (LA). Little work has been done to characterise the role of the right atrium (RA) in AF maintenance. Purpose To characterise the relative roles of the LA and RA in maintenance of atrial fibrillation and explore mechanisms of AF propagation. Methods Simultaneous bi-atrial mapping was carried out in patients undergoing first time catheter ablation using 2 linked non-contact charge density mapping systems to obtain 30-second recordings during AF. The predominant channel of communication between chambers was identified and the time difference across this channel measured (see figure). The proportion of signals earlier in each chamber was calculated and a dominant chamber identified if preceding the opposite chamber for ≥60% of the recording. AF was characterised in each chamber according to frequency of specific propagation patterns (localised rotational activation (LRA) and focal firing (FF)). The difference in AF characteristics in the LA and RA according to acute procedural outcome (termination with ablation vs. DCCV) was measured using 2-way ANOVA and predictors of AF termination identified using binomial logistic regression. Results Twenty-one patients were included (16 persistent AF, 5 paroxysmal AF, 11 in sinus rhythm at baseline) with 41 maps obtained prior to ablation. A dominant chamber was identified in 11 maps (in 9 patients). Of these, 5 maps (in 4 patients) were LA dominant, and 6 maps (in 5 patients) were RA dominant. The remainder showed balanced interatrial propagation. For patients with persistent AF, in the RA, those needing DCCV had more LRA than those with termination with ablation (79 activations, (95% CI 65-93) vs. 51 (30-71); p = 0.025). There was no difference in the LA in the two groups (77 vs 59, p = 0.541). There were fewer FFs in the RA vs LA in patients needing DCCV (123 (106-140) vs. 155 (137-172), p = 0.012)(see panel F). No differences in distribution of LIA were observed. The frequency of LRA (p = 0.003) and FF (p = 0.004) in the RA, and RA AFCL (p = 0.041), were predictors of acute procedural outcome. Conclusions Our novel approach of simultaneous bi-atrial mapping revealed that mechanisms responsible for AF maintenance were evenly distributed between atria whilst acute AF termination with left atrial ablation was dependent on the contribution of right atrial substrate. Strategies incorporating right atrial mechanisms may result in improved outcomes from AF ablation. Abstract Figure.

Quantitative proteome comparison of human hearts with those of model organisms

Delineating human cardiac pathologies and their basic molecular mechanisms relies on research conducted in model organisms. Yet translating findings from preclinical models to humans present a significant challenge, in part due to differences in cardiac protein expression between humans and model organisms. Proteins immediately determine cellular function, yet their large-scale investigation in hearts has lagged behind those of genes and transcripts. Here, we set out to bridge this knowledge gap: By analyzing protein profiles in humans and commonly used model organisms across cardiac chambers, we determine their commonalities and regional differences. We analyzed cardiac tissue from each chamber of human, pig, horse, rat, mouse, and zebrafish in biological replicates. Using mass spectrometry–based proteomics workflows, we measured and evaluated the abundance of approximately 7,000 proteins in each species. The resulting knowledgebase of cardiac protein signatures is accessible through an online database: atlas.cardiacproteomics.com. Our combined analysis allows for quantitative evaluation of protein abundances across cardiac chambers, as well as comparisons of cardiac protein profiles across model organisms. Up to a quarter of proteins with differential abundances between atria and ventricles showed opposite chamber-specific enrichment between species; these included numerous proteins implicated in cardiac disease. The generated proteomics resource facilitates translational prospects of cardiac studies from model organisms to humans by comparisons of disease-linked protein networks across species.

P387Revealing channels of interatrial communication during atrial fibrillation

Introduction Interatrial propagation has been widely studied in anatomical specimens and electrophysiological studies during sinus rhythm or pacing. However, pathways of conduction during atrial fibrillation (AF) are poorly characterised in vivo. Purpose We sought to develop a method of identifying the dominant channel of communication between atria during AF with a view to characterising the role of localised mechanisms in maintaining AF between both chambers. Methods 10 patients undergoing simultaneous bi-atrial non-contact charge density mapping before and following pulmonary vein isolation (PVI) were analysed. Simultaneous 30s recordings during AF were obtained. Virtual electrograms from every vertex of the reconstructed left and right atrial (LA, RA) anatomies were exported and phase calculated using a method of sinusoidal recomposition and Hilbert transform. For each vertex, coherence between a sequence of activations between this point and every other point on the opposing chamber was calculated using mean phase coherence (MPC). The maximum of all MPC values was assigned to this local point to estimate the degree of coherence between activity at a given point and the entire opposing chamber. The regions with highest MPC value represent the channel of communication. Each activation of this zone is then evaluated and difference in local activation time between LA and RA determined (figure). Communication between atria is determined where a normal distribution of timing shift within this channel can be demonstrated (as opposed to a uniform histogram in the case of a lack of any correlation between electrograms). If seen to be preceding the opposite chamber for ≥60% of the recording then the chamber was deemed to be leading. Results A total of 18 maps were obtained (pre-PVI only in 2). A clear channel of interatrial propagation could be seen in 17 maps (MPC value 0.48 ± 0.16) with communication within this channel demonstrated in 13 of these (MPC 0.52 ± 0.16). In the RA the most common site was in the posterior inter-caval zone (in 13) and on the posterior septum of the LA (in 14). The LA was leading in 4 maps and the RA in 2 with balanced propagation in 7. Conclusion The method of average MPC identifies channels of inter-atrial communication during AF which appear to predominantly involve posterior interatrial connections. Further application of this technique to characterise interatrial propagation may help to define patient specific phenotypes of AF and guide targeted therapy. Abstract Figure 1

Neural circuitry of capsaicin-sensitive afferents innervating submucosal arterioles in guinea pig ileum

The circuitry of capsaicin-sensitive nerves innervating submucosal arterioles in the guinea pig ileum was examined. The orientation of in vitro submucosal preparations in a double-chamber bath was varied so that nerves on differing segments of arterioles could be stimulated with capsaicin. Capsaicin-evoked dilation of preconstricted arterioles was recorded using videomicroscopy. Superfusion of capsaicin onto either proximal or distal segments of a parent arteriole divided between the chambers evoked a dilation in the opposite chamber (63 and 58%, respectively) but had no effect on extrinsically denervated preparations. When the divider separated the vascular arcades joining the two parent arterioles on the opposite or same side of the intestine, capsaicin evoked little or no response (8 and 11%, respectively). Capsaicin stimulation confined to one branch of a single vessel dilated the opposite branch (42%). In preparations with adjacently attached mucosa, application of capsaicin to the mucosa dilated arterioles in the opposite chamber. These findings suggest that capsaicin stimulation of the mucosa evokes dilation of arterioles through a submucosal reflex and that both afferent and efferent elements are confined to the submucosa and mucosa.