Enamel Carious Lesion Development in Response to Sucrose and Fluoride Concentrations and to Time of Biofilm Formation: An Artificial-Mouth Study

The aim of this study was to evaluate both sucrose and fluoride concentrations and time of biofilm formation on enamel carious lesions induced by an in vitro artificial-mouth caries model. For Study 1, biofilms formed by streptococci and lactobacilli were grown on the surface of human enamel slabs and exposed to artificial saliva containing 0.50 or 0.75 ppmF (22.5 h/d) and broth containing 3 or 5% sucrose (30 min; 3x/d) over 5 d. In Study 2, biofilms were grown in the presence of 0.75 ppmF and 3% sucrose over 3 and 9 days. Counts of viable cells on biofilms, lesion depth (LD), and the integrated mineral loss (IML) on enamel specimens were assessed at the end of the tested conditions. Counts of total viable cells and L. casei were affected by sucrose and fluoride concentrations as well as by time of biofilm formation. Enamel carious lesions were shallower and IML was lower in the presence of 0.75 ppmF than in the presence of 0.50 ppmF (P 0.25). Additionally, deeper lesions and higher IML were found after 9 d of biofilm formation (P < 0.005). Distinct sucrose concentrations did not affect enamel carious lesion development. The severity of enamel demineralization was reduced by the presence of the higher fluoride concentration. Additionally, an increase in the time of biofilm formation produced greater demineralization. Our results also suggest that the present model is suitable for studying aspects related to caries lesion development

Assessment of Ethanol and Nicotine Interactions in the Rat Model: Pharmacotherapeutics, Adolescence, and the Mesolimbic System

Indiana University-Purdue University Indianapolis (IUPUI)Alcohol use disorder (AUD) and nicotine dependence often result in serious health problems and are top contributors to preventable deaths worldwide. Co-addiction to alcohol and nicotine is the most common form of polysubstance abuse. Epidemiological studies indicate that more than 80% of individuals diagnosed with AUD concurrently use nicotine. The prevalence of alcohol and nicotine comorbidity may stem from interconnected mechanisms underlying these disorders. A better understanding of how these drugs interact and the biological basis behind the high comorbidity rates could generate key targets for the development of more effective treatments for AUD and nicotine dependence. The following experiments utilized four similar overall groups consisting of vehicle, ethanol (EtOH), nicotine (NIC), and EtOH+NIC. Chapter Two investigated the efficacy of naltrexone and varenicline, the pharmacological ‘gold standards’ for treating AUD and nicotine dependence, on voluntary drug intake by rats selectively bred for high EtOH drinking. The results indicated that the standard treatments for AUD and nicotine dependence were effective at reducing consumption of the targeted reinforcer but neither reduced EtOH+NIC co-use/abuse. Chapter Three examined the effects of peri-adolescent EtOH drinking on the ability of NIC infused into the posterior ventral tegmental area (pVTA) to stimulate dopamine release within the nucleus accumbens (NAc) shell during adulthood. The results suggest a cross-sensitization to NIC produced by peri-adolescent EtOH consumption demonstrated by a leftward and upward shift in the dose response curve. Chapter Four investigated the effects of intra-pVTA infusions on NAc shell neurochemistry, EtOH reward within the NAc shell, and the role of brain-derived neurotrophic factor (BDNF) on EtOH reward within that region. The data indicated that only EtOH+NIC significantly increased glutamate, dopamine, and BDNF in the NAc shell. Repeated pretreatment with EtOH+NIC also enhanced EtOH reward in the NAc shell and BDNF infusions were sufficient to recapitulate these findings. Collectively, the data indicate that concurrent exposure to EtOH and NIC results in unique neuroadaptations that promote future drug use. The failure to develop effective pharmacotherapeutics for AUD or nicotine dependence could be associated with examining potential targets in models that fail to reflect the impact of polydrug exposure.2020-04-0