Michal Bajo - Academia.edu (original) (raw)

Papers by Michal Bajo

Brain Behavior and Immunity, May 1, 2023

Alcohol, Jun 1, 2023

The comorbidity of posttraumatic stress disorder (PTSD) and alcohol use disorders (AUD) is preval... more The comorbidity of posttraumatic stress disorder (PTSD) and alcohol use disorders (AUD) is prevalent, complex, and difficult to treat. Cue reactivity paradigms offer a clinically relevant scientific avenue to advance our understanding of PTSD/AUD comorbidity and ultimately inform evidence-based interventions. Cue reactivity paradigms evoke emotional, behavioral, and/or Running head: PTSD/AUD AND CUE REACTIVITY 2 physiological responses by manipulating external (e.g., images, smells, scripts) cues. Through evaluation of how individuals with PTSD/AUD respond to trauma or alcohol cues (e.g., craving, distress, avoidance) in 'real' time, the theoretical framework for understanding functional associations between PTSD and AUD is refined. This brief narrative review of the recent literature (2015-present) will focus upon (1) summarizing the recently published cue reactivity studies relevant to PTSD/AUD, (2) explicating the limitations of the literature, and (3) discussing future empirical directions.

British Journal of Pharmacology, May 11, 2023

Background and PurposeChronic pain is considered a key factor contributing to alcohol use disorde... more Background and PurposeChronic pain is considered a key factor contributing to alcohol use disorder (AUD). The mechanisms responsible for chronic pain associated with chronic alcohol consumption are unknown. We evaluated the development of chronic pain in a mouse model of alcohol dependence and investigate the role of neuroinflammation.Experimental ApproachThe chronic‐intermittent ethanol two‐bottle choice CIE‐2BC paradigm generates three groups: alcohol‐dependent with escalating alcohol intake, nondependent (moderate drinking) and alcohol‐naïve control male and female mice. We measured mechanical allodynia during withdrawal and after the last voluntary drinking. Immunoblotting was used to evaluate the protein levels of IBA‐1, CSFR, IL‐6, p38 and ERK2/1 in spinal cord tissue of dependent and non‐dependent animals.Key ResultsWe found significant escalation of drinking in the dependent group in male and female compared with the non‐dependent group. The dependent group developed mechanical allodynia during 72 h of withdrawal, which was completely reversed after voluntary drinking. We observed an increased pain hypersensitivity compared with the naïve in 50% of non‐dependent group. Increased IBA‐1 and CSFR expression was observed in spinal cord tissue of both hypersensitivity‐abstinence related and neuropathy‐alcohol mice, and increased IL‐6 expression and ERK1/2 activation in mice with hypersensitivity‐related to abstinence, but not in mice with alcohol‐evoked neuropathic pain.Conclusions and ImplicationsThe CIE‐2BC model induces two distinct pain conditions specific to the type of ethanol exposure: abstinence‐related hypersensitivity in dependent mice and alcohol‐evoked neuropathic pain in about a half of the non‐dependent mice.

Genes, Brain and Behavior, May 2, 2019

The voltage-gated sodium channel subunit β4 (SCN4B) regulates neuronal activity by modulating cha... more The voltage-gated sodium channel subunit β4 (SCN4B) regulates neuronal activity by modulating channel gating and has been implicated in ethanol consumption in rodent models and human alcoholics. However, the functional role for Scn4b in ethanol-mediated behaviors is unknown. We determined if genetic global knockout or targeted knockdown of Scn4b in the central nucleus of the amygdala (CeA) altered ethanol drinking or related behaviors. We used four different ethanol consumption procedures (continuous and intermittent two-bottle choice, drinking-in-the dark, and chronic intermittent ethanol vapor) and found that male and female Scn4b knockout mice did not differ from their wild-type littermates in ethanol consumption in any of the tests. Knockdown of Scn4b mRNA in the CeA also did not alter two-bottle choice ethanol drinking. However, Scn4b knockout mice demonstrated longer duration of the loss of righting reflex induced by ethanol, gaboxadol, pentobarbital, and ketamine. Knockout mice showed slower recovery to basal levels of handling-induced convulsions after ethanol injection, which is consistent with the increased sedative effects observed in these mice. However, Scn4b knockout mice did not differ in the severity of acute ethanol withdrawal. Acoustic startle responses, ethanol-induced hypothermia, and clearance of blood ethanol also did not differ between the genotypes. There were also no functional differences in the membrane properties or excitability of CeA neurons from Scn4b knockout and wild-type mice. Although we found no evidence that Scn4b regulates ethanol consumption in mice, it was involved in the acute hypnotic effects of ethanol and other sedatives.

Alcohol and Alcoholism, May 5, 2016

Aims: Several lines of evidence support a critical role of TLR4 in the neuroimmune responses asso... more Aims: Several lines of evidence support a critical role of TLR4 in the neuroimmune responses associated with alcohol disorders and propose inhibitors of TLR4 signaling as potential treatments for alcoholism. In this work, we investigated the effect of T5342126 compound, a selective TLR4 inhibitor, on excessive drinking and microglial activation associated with ethanol dependence. Methods: We used 2BC-CIE (two-bottle choice-chronic ethanol intermittent vapor exposure) paradigm to induce ethanol dependence in mice. After induction of the ethanol dependence, we injected T5342126 (i.p., 57 mg/kg) for 14 days while monitoring ethanol intake by 2BC (limited access to ethanol) method. Results: T5342126 decreased ethanol drinking in both ethanol-dependent and non-dependent mice but T5342126 showed also dose-dependent non-specific effects represented by decreased animal locomotor activity, saccharine intake, and body core temperature. Six days after the last ethanol-drinking session, we examined the immunohistochemical staining of Iba-1 (ionized calcium-binding adapter molecule 1), a microglial activation marker, in the central nucleus of the amygdala (CeA) and dentate gyrus (DG) of the hippocampus. Notably, T5342126 reduced Iba-1 density in the CeA of both ethanol-dependent and non-dependent mice injected with T5342126. There were no significant differences in the DG Iba-1 density among the treatment groups. Conclusions: Collectively, our data suggest that T5342126, via blocking TLR4 activation, contributes to the reduction of ethanol drinking and ethanol-induced neuroimmune responses. However, the non-specific effects of T5342126 may play a significant role in the T5342126 effects on ethanol drinking and thus, may limit its therapeutic potential for treatment of alcohol dependence. Short summary: T5342126, an experimental TLR4 inhibitor, is effective in reducing ethanol drinking and inhibiting the activation and proliferation of microglia in both ethanol-dependent and nondependent mice. However, T5342126's use as a potential candidate for the treatment of alcohol addiction may be limited due to its non-specific effects.

Alcohol and Alcoholism, Jan 4, 2018

Aims: Stress induces neuroimmune responses via Toll-like receptor 4 (TLR4) activation. Here, we i... more Aims: Stress induces neuroimmune responses via Toll-like receptor 4 (TLR4) activation. Here, we investigated the role of TLR4 in the effects of the stress peptide corticotropin-releasing factor (CRF) on GABAergic transmission in the central nucleus of the amygdala (CeA) following restraint stress. Methods: Tlr4 knock out (KO) and wild-type rats were exposed to no stress (naïve), a single restraint stress (1 h) or repeated restraint stress (1 h per day for 3 consecutive days). After 1 h recovery from the final stress session, whole-cell patch-clamp electrophysiology was used to investigate the effects of CRF (200 nM) on CeA GABA A-mediated spontaneous inhibitory postsynaptic currents (sIPSCs). Results: TLR4 does not regulate baseline GABAergic transmission in the CeA of naive and stresstreated animals. However, CRF significantly increased the mean sIPSC frequencies (indicating enhanced GABA release) across all genotypes and stress treatments, except for the Tlr4 KO rats that experienced repeated restraint stress. Conclusions: Overall, our results suggest a limited role for TLR4 in CRF's modulation of CeA GABAergic synapses in naïve and single stress rats, though TLR4-deficient rats that experienced repeated psychological stress exhibit a blunted CRF cellular response. Short Summary: TLR4 has a limited role in CRF's activation of the CeA under basal conditions, but interacts with the CRF system to regulate GABAergic synapse function in animals that experience repeated psychological stress.

Addiction Biology, Jan 20, 2016

The basolateral nucleus of the amygdala (BLA) is critical to the pathophysiology of anxiety-drive... more The basolateral nucleus of the amygdala (BLA) is critical to the pathophysiology of anxiety-driven alcohol drinking and relapse. The endogenous cannabinoid/type 1 cannabinoid receptor (eCB/ CB 1) system curbs BLA-driven anxiety and stress responses via a retrograde negative feedback system that inhibits neurotransmitter release, and BLA CB 1 activation reduces GABA release and drives anxiogenesis. Additionally, decreased amygdala CB 1 is observed in abstinent alcoholic patients and ethanol withdrawn rats. Here we investigated the potential disruption of eCB/CB 1 signaling on GABAergic transmission in BLA pyramidal neurons of rats exposed to 2-3 weeks intermittent ethanol. In the naïve rat BLA, the CB 1 agonist WIN 55,212-2 (WIN) decreased GABA release and this effect was prevented by the CB 1 antagonist AM251. AM251 alone increased GABA release via a mechanism requiring postsynaptic calcium-dependent activity. This retrograde tonic eCB/CB 1 signaling was diminished in chronic ethanol exposed rats, suggesting a functional impairment of the eCB/CB 1 system. In contrast, acute ethanol increased GABAergic transmission similarly in naïve and chronic ethanol exposed rats, via both pre-and postsynaptic mechanisms. Notably, CB 1 activation impaired ethanol's facilitation of GABAergic transmission across both groups, but the AM251-and ethanol-induced facilitation of GABA release were additive, suggesting independent presynaptic sites of action. Collectively, the present findings highlight a critical CB 1 influence on BLA GABAergic transmission that is dysregulated by chronic ethanol exposure and thus, may contribute to the alcohol dependent state.

Journal of Neuroscience Research, Oct 22, 2021

Alcohol use disorder (AUD) and affective disorders are frequently comorbid and share underlying m... more Alcohol use disorder (AUD) and affective disorders are frequently comorbid and share underlying mechanisms that could be targets for comprehensive treatment. Post-traumatic stress disorder (PTSD) has high comorbidity with AUD, but comprehensive models of this overlap are nascent. We recently characterized a model of comorbid AUD and PTSD-like symptoms wherein stressed rats receive an inhibitory-avoidance (IA) related footshock on two occasions followed by two-bottle choice (2BC) voluntary alcohol drinking. Stressed rats received the second footshock in a familiar (FAM, same IA box as the first footshock) or novel context (NOV, single-chambered apparatus); the FAM paradigm more effectively increased alcohol drinking in males and the NOV paradigm in females. During abstinence, stressed males displayed avoidance-like PTSD symptoms, and females showed hyperarousal-like PTSD symptoms. Rats in the model had altered spontaneous action potential-independent GABAergic transmission in the central amygdala (CeA), a brain region key in alcohol dependence- and stress-related signaling. However, PTSD sufferers may have alcohol experience prior to their trauma. Here, we therefore modified our AUD/PTSD comorbidity model to provide 3 weeks of intermittent extended alcohol access before footshock and then studied effects of NOV and FAM stress on drinking and PTSD phenotypes. NOV stress suppressed the escalation of alcohol intake and preference seen in male controls, but no stress effects were seen on drinking in females. Additionally, NOV males had decreased action potential-independent presynaptic GABA release and delayed postsynaptic GABAA-receptor kinetics in the CeA compared to control and FAM males. Despite these changes to alcohol intake and CeA GABA signaling, stressed rats showed broadly similar anxiogenic-like behaviors to our previous comorbid model, suggesting decoupling of the PTSD symptoms from the AUD vulnerability for some of these animals. The collective results show the importance of alcohol history and trauma context in vulnerability to comorbid AUD/PTSD-like symptoms. In alcohol drinking male rats, 2-hit trauma with the second stressor in a novel context suppressed escalation of alcohol drinking compared to unshocked controls. Additionally, novel stressed males had decreased action potential-independent presynaptic GABA release and delayed postsynaptic GABAA-receptor kinetics in the CeA compared to control and familiar stressed males.

Addiction Biology, May 5, 2015

The endogenous cannabinoids (eCBs) influence the acute response to ethanol and the development of... more The endogenous cannabinoids (eCBs) influence the acute response to ethanol and the development of tolerance, dependence and relapse. Chronic alcohol exposure alters eCB levels and type 1 cannabinoid receptor (CB 1) expression and function in brain regions associated with addiction. CB 1 inhibits GABA release, and GABAergic dysregulation in the central nucleus of the amygdala (CeA) is critical in the transition to alcohol dependence. We investigated possible disruptions in CB 1 signaling of rat CeA GABAergic transmission following intermittent ethanol exposure. In the CeA of alcohol-naïve rats, CB 1 agonist WIN 55,212-2 (WIN) decreased the frequency of spontaneous and miniature GABA A receptor-mediated inhibitory postsynaptic currents (s/ mIPSCs). This effect was prevented by CB 1 antagonism, but not type 2 cannabinoid receptor (CB 2) antagonism. After 2-3 weeks of intermittent ethanol exposure, these WIN inhibitory effects were attenuated, suggesting ethanol-induced impairments in CB 1 function. The CB 1 antagonist AM251 revealed a tonic eCB/CB 1 control of GABAergic transmission in the alcohol-naïve CeA that was occluded by calcium chelation in the postsynaptic cell. Chronic ethanol exposure abolished this tonic CB 1 influence on mIPSC, but not sIPSC, frequency. Finally, acute ethanol increased CeA GABA release in both naïve and ethanol exposed rats. Although CB 1 activation prevented this effect, the AM251-and ethanol-induced GABA release were additive, ruling out a direct participation of CB 1 signaling in the ethanol effect. Collectively, these observations demonstrate an important CB 1 influence on CeA GABAergic transmission and indicate that the CeA is particularly sensitive to alcohol-induced disruptions of CB 1 signaling.

Neurobiology of Stress, Jul 1, 2023

Cells

Alcohol use disorder (AUD) and anxiety disorders are frequently comorbid and share dysregulated n... more Alcohol use disorder (AUD) and anxiety disorders are frequently comorbid and share dysregulated neuroimmune-related pathways. Here, we used our established rat model of comorbid post-traumatic stress disorder (PTSD)/AUD to characterize the interleukin 18 (IL-18) system in the central amygdala (CeA). Male and female rats underwent novel (NOV) and familiar (FAM) shock stress, or no stress (unstressed controls; CTL) followed by voluntary alcohol drinking and PTSD-related behaviors, then all received renewed alcohol access prior to the experiments. In situ hybridization revealed that the number of CeA positive cells for Il18 mRNA increased, while for Il18bp decreased in both male and female FAM stressed rats versus CTL. No changes were observed in Il18r1 expression across groups. Ex vivo electrophysiology showed that IL-18 reduced GABAA-mediated miniature inhibitory postsynaptic currents (mIPSCs) frequencies in CTL, suggesting reduced CeA GABA release, regardless of sex. Notably, this p...

Molecular Psychiatry, 2020

Alcohol use disorder (AUD) and anxiety disorders are frequently comorbid and share mechanisms tha... more Alcohol use disorder (AUD) and anxiety disorders are frequently comorbid and share mechanisms that could be therapeutic targets. To facilitate mechanistic studies, we adapted an inhibitory avoidance-based "2-hit" rat model of posttraumatic stress disorder (PTSD) and identified predictors and biomarkers of comorbid alcohol (ethanol)/PTSD-like symptoms in these animals. Stressed Wistar rats received a single footshock on two occasions. The first footshock occurred when rats crossed into the dark chamber of a shuttle box. Forty-eight hours later, rats received the second footshock in a familiar (FAM) or novel (NOV) context. Rats then received 4 weeks of two-bottle choice (2BC) ethanol access. During subsequent abstinence, PTSD-like behavior responses, GABAergic synaptic transmission in the central amygdala (CeA), and circulating cytokine levels were measured. FAM and NOV stress more effectively increased 2BC drinking in males and females, respectively. Stressed male rats, especially drinking-vulnerable individuals (≥0.8 g/kg average 2-h ethanol intake with >50% ethanol preference), showed higher fear overgeneralization in novel contexts, increased GABAergic transmission in the CeA, and a profile of increased G-CSF, GM-CSF, IL-13, IL-6, IL-17a, leptin, and IL-4 that discriminated between stress context (NOV > FAM > Control). However, drinking-resilient males showed the highest G-CSF, IL-13, and leptin levels. Stressed females showed increased acoustic startle and decreased sleep maintenance, indicative of hyperarousal, with increased CeA GABAergic transmission in NOV females. This paradigm promotes key features of PTSD, including hyperarousal, fear generalization, avoidance, and sleep disturbance, with comorbid ethanol intake, in a sex-specific fashion that approximates clinical comorbidities better than existing models, and identifies increased CeA GABAergic signaling and a distinct prohematopoietic, proinflammatory, and pro-atopic cytokine profile that may aid in treatment.

Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethan... more Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethanol and genetic variations in the channel-forming α subunit have been nominally associated with alcohol use disorders. However, whether the direct action of ethanol at BK α influences the motivation to drink alcohol remains to be determined. In the present study, we sought to investigate the behavioral relevance of this molecular interaction by introducing in the mouse genome a point mutation known to render BK channels insensitive to ethanol while preserving their physiological function. The BK α K361N substitution prevented ethanol from reducing spike threshold in medial habenula neurons. However, it did not alter acute responses to ethanolin vivo, including ataxia, sedation, hypothermia, analgesia, and conditioned place preference.Furthermore, the mutation did not have reproducible effects on alcohol consumption in limited, continuous, or intermittent access home cage two-bottle choice...

Brain, Behavior, and Immunity, 2015

British Journal of Pharmacology