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No description available.

Caffeine is the most consumed psychoactive substance in the world, and most caffeine consumption in coffee and energy drinks is intended to produce a psychoactive effect. However, caffeine is not a primary reinforcer in preclinical paradigms – non-human species do not reliably take the drug to produce a psychoactive effect. However, caffeine is a ‘reinforcement enhancer’ in preclinical models; the effects of caffeine increase the motivation to obtain other non-drug reinforcers. The overall goal of this project was to determine if these reinforcement enhancing effects of caffeine could promote caffeine self-administration and to subsequently investigate the behavioral and neurochemical underpinnings of this effect. We hypothesized reliable caffeine self-administration would occur by adventitious pairing of caffeine with saccharin, a primary reinforcer. Second, we hypothesized that caffeine enhances reinforcement by increasing the salience of incentive stimuli, which are stimuli that come to evoke approach behaviors through associative learning (e.g., Pavlovian conditioning). Finally, incentive salience is moderated by dopamine release in the nucleus accumbens (NAc), an area highly involved in reward-learning and substance dependence. Therefore, we hypothesized that if caffeine enhanced control of approach behavior by incentives, then it would increase the ability of incentive stimuli to evoke dopamine in the NAc. These studies show that intravenous delivery of caffeine with oral saccharin increases operant relative to control groups responding for intravenous caffeine or oral saccharin. The effect was also dose-dependent, confirming that the psychoactive effects of caffeine increased behavior. We also extended this effect to an oral model of caffeine self-administration, which included a simple sweetener (saccharin) or a complex oral vehicle (saccharin with decaffeinated coffee) to mask the bitter taste of caffeine. Presenting caffeine with oral saccharin promoted self-administration, relative to saccharin alone and did not depend on the nature of the complexity of the vehicle. Caffeine also dose-dependently increased approach to an incentive stimulus and this effect was associated with increased extracellular dopamine in the NAc. These findings suggest caffeine enhances incentive motivation and that this effect may result from increases in CS-evoked striatal dopamine.

In this study, the single-cell relative quantitative mRNA expression of three Calcium-binding proteins (CaBPs; calbindin, calretinin, parvalbumin) and eight nicotinic acetylcholine receptor (nAChR) subunits (alpha2-alpha5, alpha7, beta2-beta4) from interneurons from the stratum radiatum or stratum oriens within the CA1 region of rat hippocampi was analyzed using quantitative real time RT-PCR. Eighty-seven percent of the interneurons examined expressed CaBP mRNA. Parvalbumin mRNA was detected in 64%, while calbindin and calretinin expression was detected in 26% and 40% of interneurons, respectively. CaBP expression was not exclusive; the average number of CaBP mRNA detected per interneuron of the 47 interneurons examined for CaBP was 1.3. There was no significant difference between the proportion of CaBPs expressed in the stratum radiatum compared to the stratum oriens. However, interneurons from the stratum radiatum expressed significantly higher relative levels of mRNA for calbindin. Eighty-four percent of the 31 interneurons examined for both CaBP and nAChR subunits expressed nAChR subunit mRNA; the average number of nAChR subunits detected per interneuron was 2.9. Furthermore, of the 24, 140, and 168 possible combinations of 2-, 3-, and 4-way co-expression between CaBP+nAChR mRNA, respectively, only two significant 3-way combinations were detected: parvalbumin+a3+a5 and parvalbumin+alpha5+beta4. This study reports that subpopulations of nAChR-containing interneurons defined by quantitative CaBP mRNA expression or CaBP+nAChR co-expression do exist within the CA1 region of the hippocampus.

Although it is well-established that animals will self-stimulate electric current to various diverse brain structures, the neural substrate of brain stimulation reward (BSR) has eluded identification since its discovery more than a half-century ago. We show that GABA neurons in the midbrain, hypothalamus and thalamus express connexin-36 (Cx36) gap junctions and couple electrically with dopamine application or by stimulation of the internal capsule (IC), which also supports self-stimulation. The threshold for responding for self-stimulation of the IC is the threshold for coupling between these GABA neurons, the degree of responding for IC ICSS is proportional to the magnitude of electrical coupling between these GABA neurons, and GJ blockers, including the Cx36 blocker mefloquine, increase the threshold for IC self-stimulation without affecting performance. Thus, electrical coupling between this network of GABA neurons fits the prevailing model for the elusive integrator of BSR.

Whole hippocampus preparations, isolated bilaterally, from untreated Wistar rats at various ages (10-90 days old) were analyzed for the mRNA expression of the alpha 2, alpha 3, alpha 4, alpha 5, alpha 7, beta 2, beta 3, and beta 4 neuronal nicotinic acetylcholine receptor subunits. To do so, RNA was isolated from acutely isolated hippocampal samples, converted to cDNA by means of a reverse transcription reaction, then analyzed with quantitative real-time PCR to determine the relative levels of the mRNAs the cells were expressing at the age when the samples were obtained. The relative expression of the levels of RNA were then compared across age groups by subunits and across subunits by ages. The results suggest that all eight subunits are expressed throughout the life of the rat and that the subunit expression for the Hippocampus varies only slightly as a rat develops.

The purpose of this thesis project was to examine the function of connexin-36 (Cx36) gap junctions (GJs) in producing alcohol's intoxicating and rewarding effects. GABA neurons are thought to inhibit dopamine (DA) neurotransmission in the mesocorticolimbic system, which originates in the midbrain ventral tegmental area (VTA) and projects to limbic structures such as the nucleus accumbens (NAcc). The mesolimbic DA system is believed to be the neural substrate of alcohol intoxication and addiction (Tepper, Paladini, & Celada, 1998). Alcohol suppresses the firing rate of GABA neurons in the VTA (Gallegos, Criado, Lee, Henriksen, & Steffensen, 1999) and presumably disinhibits DA neurons thereby resulting in enhanced release of DA in the NAcc. Interestingly, VTA GABA neurons appear to form part of a larger syncytium of GABA neurons in the reticular formation that are linked by electrical synapses via Cx36 GJs (Allison, et al., 2006; Stobbs, et al., 2004; Lassen, et al., 2007). Gap junction blockers, including the Cx36-selective antagonist mefloquine, also suppress the excitability and electrical coupling of VTA GABA neurons (Stobbs, et al., 2004). Thus, I hypothesized that Cx36 GJs cause synchrony in VTA GABA neurons which alcohol blocks to cause intoxication and reward. To accomplish these studies I compared the effects of intoxicating doses of ethanol in Cx36 knockout (KO) mice and mefloquine-treated mice and their wild-type (WT) controls with two tests that index ataxia, an open field activity system and the fixed-speed rotarod apparatus, as well as with ethanol self-administration. I found that Cx36 KO and mefloquine-treated mice exhibit significantly more ethanol-induced loss of movement in the open field test, a paradigm which indexes gross motor activity and tremor, but less ataxia than their WT controls in the rotarod paradigm, a paradigm which indexes balance and coordination. Most importantly, both Cx36 KO and mefloquine-treated mice consumed less ethanol than their controls. These findings provide evidence in support of the hypothesis that Cx36 GJs are important targets for ethanol effects in the mesolimbic system.

A global analysis of the human proteome demonstrates that there are ~5500 tryptic fragments that contain four cysteines in close proximity. Elucidating whether they form disulfide bonds in vivo under different conditions is particularly important because cysteines are known to be a vital cellular redox sensor as well as a catalytic site for important biochemical reactions. However, currently there are no methods that can resolve disulfide patterns in closely-packed cysteine residues from a complex sample. In order to address this problem, we have developed a novel mass-spectrometry-based method to identify the different disulfide bonding patterns possible, using SNAP25B cysteine-rich region as a test case. Unlike traditional proteomics, this method uses non-reduced sample preparation, thus preserving intact disulfide bonds. It relies on collision-induced dissociation (CID) to cause double-backbone and heterolytic disulfide-bond cleavage and compares this to the theoretical MS/MS spectra. CID in an ion trap gives robust detection of double backbone cleavages and heterolytic disulfide-bond cleavages. Here, we report, for the first time, identification of all three disulfide patterns for double-disulfide species of SNAP25B using collision-induced dissociation.

Investigations of human biology and disease have been hindered by the use of animal models. The information obtained from such studies often results in clinically irrelevant results and drug trial failures. Additionally, several governing bodies have been formulating legislation to move away from animal models and toward more ethical and efficient testing platforms for drug discovery and cosmetic research. As an answer to these issues, "body-on-a-chip" systems have been a rapidly developing field which easily recapitulates in vivo functionality, providing a more relevant, repeatable, and ethical testing platform to better predict biology. These systems can be used as human-based testing platforms to evaluate human physiology, disease progression, and drug responsiveness for specific cell types and multi-organ systems. Diseases such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) have significant research challenges, specifically with translating research findings into treatment plans. The complexity of the neuromuscular reflex arc, the biological system affected by these diseases, is difficult to study with traditional molecular techniques, namely because the many components of this disease system interact with each other using complex pathways. This work pushes the existing platform to a more complete human model of neuromuscular disease with the incorporation of gamma motoneurons, development of the first human induced pluripotent cell (iPSC) derived intrafusal fibers, and proposals to incorporate nociceptive neurons all on a functionally interrogative platform. The incorporation of these components will allow for a more complete, clinically relevant model to study neuromuscular disorders and for preclinical dug discovery.