Decreased Reward Sensitivity in Rats from the Fischer344 Strain Compared to Wistar Rats Is Paralleled by Differences in Endocannabinoid Signaling

BACKGROUND: The aim of the present study was to examine if differences in the endocannabinoid (ECB) system might be linked to strain specific variations in reward-related behavior in Fischer344 (Fischer) and Wistar rats. METHODOLOGY/PRINCIPAL FINDINGS: Two rat strains, the Fischer and the Wistar strain, were tested for different aspects of reward sensitivity for a palatable food reward (sweetened condensed milk, SCM) in a limited-access intake test, a progressive ratio (PR) schedule and the pleasure-attenuated startle (PAS) paradigm. Additionally, basic differences in the ECB system and cannabinoid pharmacology were examined in both rat strains. Fischer rats were found to express lower reward sensitivity towards SCM compared to Wistar rats. These differences were observed for consummatory, motivational and hedonic aspects of the palatable food reward. Western blot analysis for the CB1 receptor and the ECB degrading enzyme fatty acid amide hydrolase (FAAH) revealed a lower expression of both proteins in the hippocampus (HPC) of Fischer rats compared to the Wistar strain. Furthermore, increased cannabinoid-stimulated extracellular-regulated kinase (ERK) phosphorylation was detected in Wistar rats compared to the Fischer strain, indicating alterations in ECB signaling. These findings were further supported by the pharmacological results, where Fischer rats were found to be less sensitive towards the effects of the CB1 receptor antagonist/inverse agonist SR141716 and the cannabinoid agonist WIN 55,212-2. CONCLUSIONS/SIGNIFICANCE: Our present findings indicate differences in the expression of the CB1 receptor and FAAH, as well as the activation of ECB signaling pathways between Fischer and Wistar rats. These basic differences in the ECB system might contribute to the pronounced differences observed in reward sensitivity between both rat strains

Risk factors for variant Creutzfeldt-Jakob disease in dental practice: a case-control study

<p>Objective: To assess the risk of variant Creutzfeldt-Jakob Disease (vCJD) associated with dental treatment.</p> <p>Design: Case-control study, investigation of links between cases.</p> <p>Setting: National CJD surveillance, general dental practice and practice boards in Great Britain, 2008-2009.</p> <p>Methods: Variant CJD cases were recruited from all those referred between May 1995 and August 2009 (n = 160); controls were recruited from the general population in 2003 using randomly selected geographic clusters and age-weighted sampling of individuals (n = 584). Risk factors were ascertained from dental records, with consent, using a structured questionnaire.</p> <p>Results: Dental records were available for fewer cases (49%, 78 out of 160) than control subjects (78%, 457 out of 584). Variant CJD cases were no more or less likely than control subjects to have undergone dental treatment (p ≥0.05). Two cases had attended the same dental practice, but the type and timing of treatments did not provide strong evidence that this was linked to the route of transmission.</p> <p>Conclusion: There is no evidence of a vCJD risk associated with dental treatment, but because dental information is limited we cannot exclude this possibility. Improved methods for dental record keeping are recommended to aid future investigations of associations between infectious diseases and dental treatment.</p&gt