Alcohol effects on synaptic transmission in periaqueductal gray dopamine neurons

The role of dopamine (DA) signaling in regulating the rewarding properties of drugs, including alcohol, has been widely studied. The majority of these studies, however, have focused on the DA neurons located in the ventral tegmental area (VTA), and their projections to the nucleus accumbens. DA neurons within the ventral periaqueductal gray (vPAG) have been shown to regulate reward but little is known about the functional properties of these neurons, or how they are modified by drugs of abuse. This lack of knowledge is likely due to the highly heterogeneous cell composition of the vPAG, with both γ-amino-butyric acid (GABA) and glutamate neurons present in addition to DA neurons. In this study, we performed whole-cell recordings in a TH–eGFP transgenic mouse line to evaluate the properties of vPAG-DA neurons. Following this initial characterization, we examined how both acute and chronic alcohol exposure modify synaptic transmission onto vPAG-DA neurons. We found minimal effects of acute alcohol exposure on GABA transmission, but a robust enhancement of glutamatergic synaptic transmission in vPAG-DA. Consistent with this effect on excitatory transmission, we also found that alcohol caused an increase in firing rate. These data were in contrast to the effects of chronic intermittent alcohol exposure, which had no significant impact on either inhibitory or excitatory synaptic transmission on the vPAG-DA neurons. These data add to a growing body of literature that points to alcohol having both region-dependent and cell-type dependent effects on function

Mu Opioid Receptor Modulation of Dopamine Neurons in the Periaqueductal Gray/Dorsal Raphe: A Role in Regulation of Pain

The periaqueductal gray (PAG) is a brain region involved in nociception modulation, and an important relay center for the descending nociceptive pathway through the rostral ventral lateral medulla. Given the dense expression of mu opioid receptors and the role of dopamine in pain, the recently characterized dopamine neurons in the ventral PAG (vPAG)/dorsal raphe (DR) region are a potentially critical site for the antinociceptive actions of opioids. The objectives of this study were to (1) evaluate synaptic modulation of the vPAG/DR dopamine neurons by mu opioid receptors and to (2) dissect the anatomy and neurochemistry of these neurons, in order to assess the downstream loci and functions of their activation. Using a mouse line that expresses eGFP under control of the tyrosine hydroxylase (TH) promoter, we found that mu opioid receptor activation led to a decrease in inhibitory inputs onto the vPAG/DR dopamine neurons. Furthermore, combining immunohistochemistry, optogenetics, electrophysiology, and fast-scan cyclic voltammetry in a TH-cre mouse line, we demonstrated that these neurons also express the vesicular glutamate type 2 transporter and co-release dopamine and glutamate in a major downstream projection structure—the bed nucleus of the stria terminalis. Finally, activation of TH-positive neurons in the vPAG/DR using Gq designer receptors exclusively activated by designer drugs displayed a supraspinal, but not spinal, antinociceptive effect. These results indicate that vPAG/DR dopamine neurons likely play a key role in opiate antinociception, potentially via the activation of downstream structures through dopamine and glutamate release

Chronic stress alters neuropeptide Y signaling in the bed nucleus of the stria terminalis in DBA/2J but not C57BL/6J mice

Numerous rodent and human studies have demonstrated that neuropeptide Y (NPY) is involved in the regulation of anxiety-related behaviors. In this study, we examined whether there were differences in NPY signaling between two inbred mouse strains (C57BL/6J and DBA/2J) that exhibit divergent basal and stress-induced anxiety phenotypes. We focused on the bed nucleus of the stria terminals (BNST), a structure in the extended amygdala that is important for the regulation of anxiety-like behavior and contains NPY receptors. While results from whole-cell voltage-clamp recordings and immunofluorescence histochemistry revealed no significant basal differences in NPY signaling or NPY and NPY Y2 receptor (Y2R) expression in the BNST, these measures were differentially altered by chronic restraint stress. Ten days of chronic restraint stress increased basal GABAergic transmission and decreased NPY’s ability to inhibit evoked GABAergic transmission in the dorsolateral BNST (dlBNST) via Y2R in DBA/2J, but not C57BL/6J, mice. Additionally, restraint stress increased NPY and Y2R expression across subregions of the BNST of DBA/2J mice 24 hrs after the last stress exposure, but no changes were observed in C57BL/6J mice. Together, these results suggest that chronic restraint stress engages the NPY system and alters NPY modulation of inhibitory transmission in the dlBNST of DBA/2J mice, but not C57BL/6J mice, which may be related to increased expression of anxiety-related behaviors in this strain

Visual and olfactory associative learning in the malaria vector Anopheles gambiae sensu stricto

<p>Abstract</p> <p>Background</p> <p>Memory and learning are critical aspects of the ecology of insect vectors of human pathogens because of their potential effects on contacts between vectors and their hosts. Despite this epidemiological importance, there have been only a limited number of studies investigating associative learning in insect vector species and none on Anopheline mosquitoes.</p> <p>Methods</p> <p>A simple behavioural assays was developed to study visual and olfactory associative learning in <it>Anopheles gambiae</it>, the main vector of malaria in Africa. Two contrasted membrane qualities or levels of blood palatability were used as reinforcing stimuli for bi-directional conditioning during blood feeding.</p> <p>Results</p> <p>Under such experimental conditions <it>An. gambiae </it>females learned very rapidly to associate visual (chequered and white patterns) and olfactory cues (presence and absence of cheese or Citronella smell) with the reinforcing stimuli (bloodmeal quality) and remembered the association for up to three days. Associative learning significantly increased with the strength of the conditioning stimuli used. Importantly, learning sometimes occurred faster when a positive reinforcing stimulus (palatable blood) was associated with an innately preferred cue (such as a darker visual pattern). However, the use of too attractive a cue (e.g. Shropshire cheese smell) was counter-productive and decreased learning success.</p> <p>Conclusions</p> <p>The results address an important knowledge gap in mosquito ecology and emphasize the role of associative memory for <it>An. gambiae</it>'s host finding and blood-feeding behaviour with important potential implications for vector control.</p

Effect of Axillary Dissection vs No Axillary Dissection on 10-Year Overall Survival Among Women With Invasive Breast Cancer and Sentinel Node Metastasis: The ACOSOG Z0011 (Alliance) Randomized Clinical Trial

The results of the American College of Surgeons Oncology Group Z0011 (ACOSOG Z0011) trial were first reported in 2005 with a median follow-up of 6.3 years. Longer follow-up was necessary because the majority of the patients had estrogen receptor–positive tumors that may recur later in the disease course (the ACOSOG is now part of the Alliance for Clinical Trials in Oncology)

Effects of chronic ethanol exposure on neuronal function in the prefrontal cortex and extended amygdala

Chronic alcohol consumption and withdrawal leads to anxiety, escalated alcohol drinking behavior, and alcohol dependence. Alterations in the function of key structures within the cortico-limbic neural circuit have been implicated in underlying the negative behavioral consequences of chronic alcohol exposure in both humans and rodents. Here, we used chronic intermittent ethanol vapor exposure (CIE) in male C57BL/6J mice to evaluate the effects of chronic alcohol exposure and withdrawal on anxiety-like behavior and basal synaptic function and neuronal excitability in prefrontal cortical and extended amygdala brain regions. Forty-eight hours after four cycles of CIE, mice were either assayed in the marble burying test (MBT) or their brains were harvested and whole-cell electrophysiological recordings were performed in the prelimbic and infralimbic medial prefrontal cortex (PLC and ILC), the lateral and medial central nucleus of the amygdala (lCeA and mCeA), and the dorsal and ventral bed nucleus of the stria terminalis (dBNST and vBNST). Ethanol-exposed mice displayed increased anxiety in the MBT compared to air-exposed controls, and alterations in neuronal function were observed in all brain structures examined, including several distinct differences between subregions within each structure. Chronic ethanol exposure induced hyperexcitability of the ILC, as well as a shift toward excitation in synaptic drive and hyperexcitability of vBNST neurons; in contrast, there was a net inhibition of the CeA. This study reveals extensive effects of chronic ethanol exposure on the basal function of cortico-limbic brain regions, suggests that there may be complex interactions between these regions in the regulation of ethanol-dependent alterations in anxiety state, and highlights the need for future examination of projection-specific effects of ethanol in cortico-limbic circuitry

G protein-gated potassium channels in ventral tegmental area dopamine neurons temper behavioral sensitivity to cocaine

University of Minnesota Ph.D. dissertation. February 2019. Major: Neuroscience. Advisor: Kevin Wickman. 1 computer file (PDF); xi, 197 pages.Drugs of abuse share the ability to enhance dopamine (DA) release in the mesocorticolimbic system. This increase in DA is thought to drive persistent adaptations in the brain and behavior that contribute to the progression of addiction. One such adaptation is a cocaine exposure-induced suppression of G protein-dependent inhibitory signaling in DA neurons of the ventral tegmental area (VTA), a cell population important for reward-related behavior. This cocaine-induced adaptation involves the internalization of G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels, a key contributor to inhibitory G protein pathways that normally temper DA neurotransmission in the mesocorticolimbic system. Dopamine 2 receptor (D2R) activation mediates this adaptation. While methamphetamine, another psychostimulant, can induce a similar adaptation in inhibitory G protein signaling, other drugs of abuse, i.e. morphine, are unable to induce a GIRK channel adaptation. Thus, inhibitory G protein signaling in VTA DA neurons could be important for tempering the behavioral response to cocaine, and could represent an inhibitory “barrier” to addiction. The goal of this thesis research is to understand the impact of GIRK channel activity signaling on behavioral sensitivity to cocaine. The work in this thesis tests the hypothesis that the strength of inhibitory G protein signaling in VTA DA neurons is inversely related to behavioral sensitivity to cocaine. This hypothesis predicts decreasing GIRK channel activity in DA neurons will increase behavioral sensitivity to cocaine. To test this, a genetic strategy was employed, to ablate GIRK channels in DA neurons using DATCre(+):Girk2fl/fl mice. The strength of two significant G protein receptor-dependent signaling dependent on GIRK channels were significantly reduced in a dopamine neuron-specific manner. DATCre(+):Girk2fl/fl mice displayed increased locomotor responding to both acute and repeated cocaine, as well as increased responding for, and intake of, cocaine in intravenous self-administration. The DATCre(+):Girk2fl/fl manipulation parallels the cocaine-induced suppression of GIRK-dependent signaling in VTA DA neurons, and suggests the GIRK channel in DA neurons temper behavioral sensitivity to cocaine. This hypothesis was further tested in a VTA-specific manner using a Cre-dependent viral approach, overexpressing GIRK channels with opposing functional roles. The overexpression of GIRK2 increased inhibitory G protein signaling and decreased cocaine-induced locomotion, while conversely, overexpression of GIRK3 decreased inhibitory G protein signaling and increased cocaine-induced locomotion. Overall, this supports the hypothesis GIRK channel activity in VTA DA neurons tempers behavioral sensitivity to drugs of abuse. In addition to addiction, VTA DA neurons have been implicated in negative affective behaviors, notably following stress. Interestingly, manipulating GIRK channel activity did not alter depression- and anxiety-related behavior, suggests that inhibitory signaling in VTA DA neurons mediated by GIRK channels plays a minimal role in negative affective behaviors, at least in non-stress conditions. However, footshock, a more severe form of stress, elicited adaptations in GIRK channel activity in VTA DA neurons, suggesting that GIRK channel activity could influence behavior following stress. Taken together, the work in this thesis suggests the GIRK channel present in VTA DA neurons contributes to the behavioral effects of cocaine, and could represent a promising therapeutic target for psychostimulant addiction

Asyms©-serat:A side-effect risk assessment tool to predict chemotherapy related toxicity in patients with cancer receiving chemotherapy

Patients undergoing chemotherapy want specific information on potential toxicities of their treatment. Such information includes what side-effects they are likely to experience, how severe these side-effects will be, how long they will experience them for, and the best ways of managing them. As well as improving the experiences of patients, information about potential side-effects may also be of significant benefit clinically, as patients who are ‘at risk’ of developing certain toxicities may be identified, facilitating more targeted, cost-effective interventions. This paper describes research which uses risk modelling techniques for identifying patterns in patient side-effect data to aid in predicting side-effects patients are likely to experience. Through analysis of patient data, a patient can receive information specific to the symptoms they are likely to experience. A user-friendly software tool SERAT (Side-Effect Risk Assessment Tool) has been developed, which presents side-effect information to the patients both at the start of treatment and reviews and monitors predictions with each new cycle of chemotherapy received