Adrenoceptor Research Articles

Locus Coeruleus and Noradrenergic Pharmacology in Neurodegenerative Disease.

Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α1-AR, α2-AR, and β-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.

Antiulcer mechanisms of the hydroalcoholic extract from Aztec marigolds' medicinal and edible flowers (Tagetes erecta L.).

The antiulcer mechanisms of the dry extract of T. erecta flowers (DETe) were studied here. The acute ulcers induced by acidified ethanol or indomethacin were reproduced in mice pretreated with DETe (3 - 300 mg/kg). The antiulcer activity of DETe was also verified in mice pretreated with NEM, L-NAME, indomethacin, or yohimbine. The antisecretory effect of DETe was verified in rats, and its anti-Helicobacter pylori activity was determined in vitro. DETe (300 mg/kg, p.o) reduced the ethanol- or indomethacin-induced ulcer by 49 and 93%, respectively. The pre-treatment with L-NAME, NEM or yohimbine abolished the gastroprotective effect of DETe. However, DETe did not change the volume, acidity, or peptic activity in rats and did not affect H. pylori. This study expands knowledge about the antiulcerogenic potential of DETe, evidencing the role of nitric oxide, non-protein sulfhydryl groups, α2 adrenergic receptors, and prostaglandins, but not antisecretory or anti-H. pylori properties.

A PAM of the α1A-Adrenergic receptor rescues biomarker, long-term potentiation, and cognitive deficits in Alzheimer’s disease mouse models without effects on blood pressure

α1-Adrenergic Receptors (ARs) regulate the sympathetic nervous system by the binding of norepinephrine (NE) and epinephrine (Epi) through different subtypes (α1A, α1B, α1D). α1A-AR activation is hypothesized to be memory forming and cognitive enhancing but drug development has been stagnant due to unwanted side effects on blood pressure. We recently reported the pharmacological characterization of the first positive allosteric modulator (PAM) for the α1A-AR with predictive pro-cognitive and memory properties. In this report, we now demonstrate the in vivo characteristics of Compound 3 (Cmpd-3) in two genetically-different Alzheimer’s Disease (AD) mouse models. Drug metabolism and pharmacokinetic studies indicate sufficient brain penetrance and rapid uptake into the brain with low to moderate clearance, and a favorable inhibition profile against the major cytochrome p450 enzymes. Oral administration of Cmpd-3 (3–9 mg/kg QD) can fully rescue long-term potentiation defects and AD biomarker profile (amyloid β-40, 42) within 3 months of dosing to levels that were non-significant from WT controls and which outperformed donepezil (1 mg/kg QD). There were also significant effects on paired pulse facilitation and cognitive behavior. Long-term and high-dose in vivo studies with Cmpd-3 revealed no effects on blood pressure. Our results suggest that Cmpd-3 can maintain lasting therapeutic levels and efficacy with disease modifying effects with a once per day dosing regimen in AD mouse models with no observed side effects.

Structures of Adrenoceptors.

The first structure of an adrenoceptor (AR), the human β2-adrenoceptor (hβ2AR) was published in 2007 and since then a total of 78 structures (up to June 2022) have been determined by X-ray crystallography and electron cryo-microscopy (cryo-EM) of all three βARs (β1, β2 and β3) and four out of six αARs (α1B, α2A, α2B, α2C). The structures are in a number of different conformational states, including the inactive state bound to an antagonist, an intermediate state bound to agonist and active states bound to agonist and an intracellular transducer (G protein or arrestin) or transducer mimetic (nanobody). The structures identify molecular details of how ligands bind in the orthosteric binding pocket (OBP; 19 antagonists, 18 agonists) and also how three different small molecule allosteric modulators bind. The structures have been used to define the molecular details of receptor activation and also the molecular determinants for transducer coupling. This chapter will give a brief overview of the structures, receptor activation, a comparison across the different subfamilies and commonalities of ligand-receptor interactions.

A review of neuroprotective mechanisms of dexmedetomidine

Dexmedetomidine (DEX) is a highly specific and effective α2-adrenergic receptor agonist. Due to its high protein binding rate, intravenous pumping can play a good role in sedation and hypnosis, analgesia, anti-anxiety, reducing inflammation, and so on, so it has been widely used in clinical anesthesia and basic research. In recent years, with the further study of dexmedetomidine, it has been found that it has a certain protective effect on nerve injury caused by various causes.

A-80426 suppresses CFA-induced inflammatory pain by suppressing TRPV1 activity via NFκB and PI3K pathways in mice

ObjectivesPain is associated with many circumstances, including inflammatory reactions, which arise from modification of the features of signaling pathways. α2-adrenergic receptor antagonists are widely utilized in narcosis. Here, the authors focused on the narcotic effect of A-80426 (A8) on Complete Freund's Adjuvant (CFA) injections-triggered chronic inflammation pain in WT and TRPV1-/- mice and explored whether its antinociceptive impact was modulated via Transient Receptor Potential Vanilloid 1 (TRPV1). MethodCFA with or without A8 was co-administered to the mice, which were categorized randomly into four groups: CFA, A8, control, and vehicle. Pain behaviors underwent evaluation through mechanical withdrawal threshold, abdominal withdrawal reflex, and thermal withdrawal latency of WT animals. ResultsQuantitative polymerase chain reaction revealed that inflammation-promoting cytokines (IL-1β, IL-6, and TNF-α) were upregulated in Dorsal Root Ganglion (DRG) and Spinal Cord Dorsal Horn (SCDH) tissues of WT animals. A8 administration reduced the pain behaviors and production of pro-inflammatory cytokines; however, this effect was significantly reduced in TRPV1-/- mice. Further analysis showed that CFA treatment reduced the TRPV1 expression in WT mice and A8 administration increased its expression and activity. The co-administration of SB-705498, a TRPV1 blocker, did not influence the pain behaviors and inflammation cytokines in CFA WT mice; however, SB-705498 the effect of A8 in WT mice. In addition, the TRPV1 block decreased the NFκB and PI3K activation in the Dorsal Root Ganglia (DRG) and Spinal Cord Dorsal Horn (SCDH) tissues of WT mice. ConclusionsTogether, A8 exerted a narcotic impact on CFA-supplemented mice via the TRPV1-modulated NFκB and PI3K pathway.

Dexmedetomidine Attenuates Methotrexate-Induced Neurotoxicity and Memory Deficits in Rats through Improving Hippocampal Neurogenesis: The Role of miR-15a/ROCK-1/ERK1/2/CREB/BDNF Pathway Modulation.

Methotrexate (MTX) is a widely used neurotoxic drug with broad antineoplastic and immunosuppressant spectra. However, the exact molecular mechanisms by which MTX inhibits hippocampal neurogenesis are yet unclear. Dexmedetomidine (Dex), an α2-adrenergic receptor agonist, has recently shown neuroprotective effects; however, its full mechanism is unexplored. This study investigated the potential of Dex to mitigate MTX-induced neurotoxicity and memory impairment in rats and the possible role of the miR-15a/ROCK-1/ERK1/2/CREB/BDNF pathway. Notably, no former studies have linked this pathway to MTX-induced neurotoxicity. Male Sprague Dawley rats were placed into four groups. Group 1 received saline i.p. daily and i.v. on days 8 and 15. Group 2 received Dex at 10 μg/kg/day i.p. for 30 days. Group 3 received MTX at 75 mg/kg i.v. on days 8 and 15, followed by four i.p. doses of leucovorin at 6 mg/kg after 18 h and 3 mg/kg after 26, 42, and 50 h. Group 4 received MTX and leucovorin as in group 3 and Dex daily dosages as in group 2. Bioinformatic analysis identified the association of miR-15a with ROCK-1/ERK1/2/CREB/BDNF and neurogenesis. MTX lowered hippocampal doublecortin and Ki-67, two markers of neurogenesis. This was associated with the downregulation of miR-15a, upregulation of its target ROCK-1, and reduction in the downstream ERK1/2/CREB/BDNF pathway, along with disturbed hippocampal redox state. Novel object recognition and Morris water maze tests demonstrated the MTX-induced memory deficiencies. Dex co-treatment reversed the MTX-induced behavioral, biochemical, and histological alterations in the rats. These neuroprotective actions could be partly mediated through modulating the miR-15a/ROCK-1/ERK1/2/CREB/BDNF pathway, which enhances hippocampal neurogenesis.

The Effect of Tamsulosin, Dutasteride Monotherapy and Tamsulosin-Dutasteride Combination on Prostate Smooth Muscle Contractility in BPH Model Wistar Strain Rattus Novergicus.

Following the c In the management of BPH, Tamsulosin is an example of a-adrenergic receptor blocker drug that is usually used. In addition, dutasteride is also a BPH drug that works as a group of 5 a reductase inhibitor. However, the weakness of long-term administration of a1-adrenergic receptor antagonists can result in upregulation of prostate smooth muscle cell contractility and expression of a-adrenergic mRNA receptors, resulting in hyperactivity and supersensitivity to a-agonists. Our study aimed to determine the effect of long-term administration of tamsulosin, dutasteride and tamsulosin-dutasteride combination on the contractility of prostate smooth muscle cells in BPH model rats. This study was designed using an experimental post test only method, control group design. It measured the contractility of prostate smooth muscle cells from samples obtained from the prostatic stroma of experimental animals adult male Rattus norvegicus Wistar strain induced BPH and administered tamsulosin 1 mg/kg/day, dutasteride 0.5 mg/kg/day, and a combination of continuous administration for 1, 6 and 12 consecutive days. Data were analyzed using one way ANOVA if the data distribution was normal or Kruskall Walis if the data distribution was abnormal. The effect of tamsulosin, dutasteride and the combination of tamsulosin with dutasteride on prostate smooth muscle cell contractility in experimental animals Rattus norvegicus Wistar strain showed that tamsulosin administration for six days, twelve days, and the combination of tamsulosin dutasteride for one day got statistically significant different result (p=0.016; p=0.006; p=0.029) compared to the negative control group. In addition, there was a difference between the tamsulosin and dutasteride combination group for 12 days compared to tamsulosin monotherapy for 6 days and 12 days (p=0.160; p=0.010). Continuous administration of monotherapy tamsulosin has an upregulation effect on the sixth to twelfth day. Decreased contractility of prostate smooth muscle cells occurs on the first day but will increase on the sixth to twelfth day. On the other hand, the results of our study also showed that the combination of tamsulosin and dutasteride gave the effect of reducing contractility and was most effective on day 12.

The differences in the adrenergic receptors of proximal urethra between sexes.

The bladder and urethra work as a physiologically functional unit to facilitate continence in the storage and voiding phase. Sex differences have been found in the urethral contraction in response to α-adrenergic receptor activation. This study aimed to investigate the role of adrenergic receptors in the proximal urethra of male and female mice. Urinary bladder and proximal urethral smooth muscle (USM) samples from male and female C57BL/6 mice were isolated and mounted in an organ bath. Acetylcholine-induced contraction of the urinary bladder was compared in male and female mice. Phenylephrine and norepinephrine (NE) induced little contraction at a lower concentration, but a relaxing phase of female proximal USM was observed at a higher concentration. This contraction profile was inhibited by NG-nitro-L-arginine, lidocaine, and capsaicin. In addition, the NE-induced contraction was greater in the incubation of propranolol than that of L-NNA or lidocaine. These results suggested that the β-adrenoceptor may be the dominant receptor of female proximal USM, and the activity of calcitonin gene-related peptide sensory nerves and nitrergic nerves may pose an anti-contraction effect on the proximal urethra in female mice. β-adrenoceptor may be the dominant receptor of female proximal USM. The use of β-adrenergic receptor blocker agents might have the potential for the treatment of female voiding dysfunction.

The Effect Of Continuously Dutasteride Monotherapy on The Expression Of Protein Kinase C-Alpha Enzyme In BPH Model Of Wistar Strain Rattus Novergicus Rat.

Benign prostate hyperplasia (BPH) is frequently found in the elderly and significantly impacts the quality of life. One of the risk factors that induce BPH is the androgen hormone. One of the effective medications in reducing the severity of Lower Urinary Tract Symptoms caused by BPH is the α-adrenergic receptor 5α-reductase inhibitor. The study aims to see the effect of long-term dutasteride on the expression of the PKC-α enzyme in prostatic stromal tissue in the BPH Model of Wistar strain Rattus norvegicus rats. This study was an experimental, post-test-only, control group design that used randomization in sample selection. The objective is to measure the expression of PKC-α enzyme from prostate tissue of an adult male Wistar Strain of Rattus Novergicus rat that was given testosterone to induce BPH and given dutasteride in 1,3 and 6 days continuously. Data is shown in mean±SD, and all of the data were analyzed using the software SPSS 21st version with the One Way ANOVA Statistical method after fulfilling the normality test and variant homogeneity test. Data analysis with confidence rate 95% and a=0,05. There was a decrease of PKC-α enzyme and prostate weight in dutasteride monotherapy in 1,3,6 days compared to the positive control, and the lowest value was on the sixth day (SD ± 2876.8). There was a constant decrease of PKC-α enzyme from the first day until the sixth day. In conclusion, long-term dutasteride monotherapy could significantly decrease the level of PKC-α enzyme. There was no upregulation of the PKC-α enzyme in the long term of dutasteride monotherapy.

The Effect of Long-Term Tamsulosin Monotherapy and Tamsulosin - Dutasteride Combination Therapy on PKC-α Enzyme Expression in Prostate Stromal Tissue.

The α-adrenergic receptor antagonist is the most effective medical therapy to reduce the dynamic component in patients with BPH. However, long-term administration of receptor antagonists can cause upregulation of mRNA receptor expression, resulting in tolerance of drug effectiveness. PKC-α is involved in the process of prostate smooth muscle contraction through activation of the voltage-gated Ca2+ conducted canal, influenced by androgen hormones, especially testosterone, and has an isoform with Twist1, a transcription factor that plays a role in up-regulation of androgen receptors. The aim of the study was to compare the effect of long-term tamsulosin monotherapy and tamsulosin - dutasteride combination therapy in PKC-α enzyme expression in prostate stromal tissue of Rattus norvegicus rats of Wistar strain. Out of 80 samples of Rattus norvegicus rats were divided into 8 groups with different interventions: negative control group, positive control group, tamsulosin monotherapy administration for 1 day, 3 day, and 6 day groups, and tamsulosin - dutasteride combination therapy for 1 day, 3 day, and 6 day groups. BPH was induced with 3 mg/kg of testosterone proprionate for 3 weeks, continued with drugs administration according to intervention grouping. Prostate stromal tissue was taken and prepared for PKC-α enzyme measurement with ELISA method. There was a significant difference (p<0.05) in the effect of tamsulosin monotherapy and tamsulosin-dutasteride combination therapy on the PKC-α expression. There was a strong positive relationship between the duration of tamsulosin-dutasteride combination therapy on the PKC-α expression, which means the longer the duration of the combination of tamsulosin-dutasteride combination the higher the PKC-α expression. Administration of long-term tamsulosin - dutasteride combination therapy causes upregulation PKC-α expression more than tamsulosin only.

Evaluation of the effects of phenylephrine and prazosin injection into basolateral amygdala on the post-stress experience of memory retrieval in rats

The present study explored the effect of α1-adrenergic receptors in the basolateral amygdala (BLA) on memory formation in the hippocampus under repeated stress. Male rats received injections of the α1-adrenergic receptor agonist (phenylephrine) or antagonist (prazosin) bilaterally into the BLA five min before foot-shock stress, and emotional and spatial memory and in-vivo long-term potentiation (LTP) in the Cornu Ammonis (CA1) region of the hippocampus were examined. Foot-shock stress impaired performance in emotional and spatial memory tests. However, it had no significant effect on any of the LTP parameters in the hippocampus. Intra-BLA phenylephrine injection significantly impaired emotional and spatial memory performance in stressed animals. On the other hand, administration of intra-BLA prazosin significantly reduced emotional and spatial memory in the control (intact) animals. Neither of the two drugs had any significant effects on LTP parameters. Prazosin effectively impaired memory in the control, but not in the stressed rats. Stress appears to have suppressed the effect of prazosin, and it seems to be a significantly stronger stimulus than prazosin. Taken together, these findings provide new insights into the effects of α1-adrenergic receptors in the BLA on memory storage, during the stress experience.

Novel Arylpiperazine Derivatives of Salicylamide with α1-Adrenolytic Properties Showed Antiarrhythmic and Hypotensive Properties in Rats.

Cardiovascular diseases remain one of the leading causes of death worldwide. Unfortunately, the available pharmacotherapeutic options have limited effectiveness. Therefore, developing new drug candidates remains very important. We selected six novel arylpiperazine alkyl derivatives of salicylamide to investigate their cardiovascular effects. Having in mind the beneficial role of α1-adrenergic receptors in restoring sinus rhythm and regulating blood pressure, first, using radioligand binding assays, we evaluated the affinity of the tested compounds for α-adrenergic receptors. Our experiments revealed their high to moderate affinity for α1- but not α2-adrenoceptors. Next, we aimed to determine the antiarrhythmic potential of novel derivatives in rat models of arrhythmia induced by adrenaline, calcium chloride, or aconitine. All compounds showed potent prophylactic antiarrhythmic activity in the adrenaline-induced arrhythmia model and no effects in calcium chloride- or aconitine-induced arrhythmias. Moreover, the tested compounds demonstrated therapeutic antiarrhythmic activity, restoring a normal sinus rhythm immediately after the administration of the arrhythmogen adrenaline. Notably, none of the tested derivatives affected the normal electrocardiogram (ECG) parameters in rodents, which excludes their proarrhythmic potential. Finally, all tested compounds decreased blood pressure in normotensive rats and reversed the pressor response to methoxamine, suggesting that their hypotensive mechanism of action is connected with the blockade of α1-adrenoceptors. Our results confirm the antiarrhythmic and hypotensive activities of novel arylpiperazine derivatives and encourage their further investigation as model structures for potential drugs.

The mechanism of antidepressant action of a new 3-substituted thiethane-1,1-dioxide derivative in tests of neuropharmacological interaction

Introduction: The present study is aimed at investigation of the mechanism of action of a new 3-substituted thi­etane-1,1-dioxide derivative (N-199/1) exhibiting antidepressant properties, in several tests of neuropharmaco­logical interaction.&#x0D; Materials and methods: To study the mechanism of action of N-199/1, its effect on 5-hydroxytryptophan (5-HTP)-induced head-twitch response (50 mg/kg and 300 mg/kg), haloperidol-induced catalepsy (1 mg/kg), arecoline-induced tremor (6 mg/kg), picrotoxin-induced seizures (6 mg/kg) and hypothermia, induced by apomorphine (10 mg/kg) or L-3,4-dihydroxyphenylalanine (L-DOPA, 140 mg/kg), was assessed when administered singly to white outbred male mice at a dose of 2 mg/kg.&#x0D; Results and discussion: N-199/1 reduced the number of head twitches, induced by 5-HTP (300 mg/kg), by 83% 45 min after 5-HTP injection; decreased the duration of haloperidol catalepsy by 1–32 s 15–45 min after haloperidol injection; attenuated L-DOPA-induced hypothermia by 0.7 °С and apomorphine-induced hypothermia by 0.6 °С at the timepoint of 30 min; reduced the duration and severity of arecoline tremor and did not affect the convulsive effect of picrotoxin.&#x0D; Conclusion: N-199/1 acts on serotonergic, noradrenergic, dopaminergic and cholinergic neurotransmission and does not affect neuronal reuptake of monoamines or monoamine oxidase. The mechanism of action of N-199/1 is probably due to stimulation of serotonergic 5HT1A-receptors and/or blockade of 5HT2A/2C-receptors and/or α2-adrenergic receptors; dopaminergic and cholinergic receptors may also be involved.&#x0D; Graphical abstract:

Treatment of prolonged clonidine-induced autonomic instability with midodrine: a case report about a new approach or a cautionary tale?

Abstract Background Clonidine is a centrally acting α2 adrenergic and imidazoline-1 receptor agonist that can cause somnolence, bradycardia, and hypotension within several hours of ingestion. Less well-described but observed by us locally is the observation that patients presenting after large overdoses including clonidine can have prolonged autonomic instability. As a result, they may require many days in hospital before recovery. We have previously used midodrine as an indirect antagonist with good effect; however, there are no previous reports of its use for this indication. Case presentation We present the case of a young female patient who developed prolonged autonomic instability following a large overdose of clonidine (coingested with smaller doses of escitalopram + lisdexamfetamine) that was treated with midodrine but complicated by a type 2 non-ST segment elevated myocardial infarction. Conclusion Midodrine seems to ameliorate this protracted instability and may provide a means to decrease hospital length of stay in appropriate individuals.

Correlation between Adrenoceptor Expression and Clinical Parameters in Degenerated Lumbar Intervertebral Discs

Despite advanced knowledge of the cellular and biomechanical processes of intervertebral disc degeneration (IVDD), the trigger and underlying mechanisms remain unclear. Since the sympathetic nervous system (SNS) has been shown to exhibit catabolic effects in osteoarthritis pathogenesis, it is attractive to speculate that it also influences IVDD. Therefore, we explored the adrenoceptor (AR) expression profile in human IVDs and correlated it with clinical parameters of patients. IVD samples were collected from n = 43 patients undergoing lumbar spinal fusion surgery. AR gene expression was analyzed by semi-quantitative polymerase chain reaction. Clinical parameters as well as radiological Pfirrmann and Modic classification were collected and correlated with AR expression levels. In total human IVD homogenates α1A-, α1B-, α2A-, α2B-, α2C-, β1- and β2-AR genes were expressed. Expression of α1A- (r = 0.439), α2A- (r = 0.346) and β2-AR (r = 0.409) showed a positive and significant correlation with Pfirrmann grade. α1A-AR expression was significantly decreased in IVD tissue of patients with adjacent segment disease (p = 0.041). The results of this study indicate that a relationship between IVDD and AR expression exists. Thus, the SNS and its neurotransmitters might play a role in IVDD pathogenesis. The knowledge of differential AR expression in different etiologies could contribute to the development of new therapeutic approaches for IVDD.

Dexmedetomidine Attenuates Lipopolysaccharide-Induced Sympathetic Activation and Sepsis via Suppressing Superoxide Signaling in Paraventricular Nucleus.

Sympathetic overactivity contributes to the pathogenesis of sepsis. The selective α2-adrenergic receptor agonist dexmedetomidine (DEX) is widely used for perioperative sedation and analgesia. We aimed to determine the central roles and mechanisms of DEX in attenuating sympathetic activity and inflammation in sepsis. Sepsis was induced by a single intraperitoneal injection of lipopolysaccharide (LPS) in rats. Effects of DEX were investigated 24 h after injection of LPS. Bilateral microinjection of DEX in the paraventricular nucleus (PVN) attenuated LPS-induced sympathetic overactivity, which was attenuated by the superoxide dismutase inhibitor DETC, cAMP analog db-cAMP or GABAA receptor antagonist gabazine. Superoxide scavenger tempol, NADPH oxidase inhibitor apocynin, adenylate cyclase inhibitor SQ22536 or PKA inhibitor Rp-cAMP caused similar effects to DEX in attenuating LPS-induced sympathetic activation. DEX inhibited LPS-induced superoxide and cAMP production, as well as NADPH oxidase, adenylate cyclase and PKA activation. The roles of DEX in reducing superoxide production and NADPH oxidase activation were attenuated by db-cAMP or gabazine. Intravenous infusion of DEX inhibited LPS-induced sympathetic overactivity, NOX activation, superoxide production, TNF-α and IL-1β upregulation in the PVN and plasma, as well as lung and renal injury, which were attenuated by the PVN microinjection of yohimbine and DETC. We conclude that activation of α2-adrenergic receptors with DEX in the PVN attenuated LPS-induced sympathetic overactivity by reducing NADPH oxidase-dependent superoxide production via both inhibiting adenylate cyclase-cAMP-PKA signaling and activating GABAA receptors. The inhibition of NADPH oxidase-dependent superoxide production in the PVN partially contributes to the roles of intravenous infusion of DEX in attenuating LPS-induced sympathetic activation, oxidative stress and inflammation.

Characterization of a novel positive allosteric modulator of the α1A-Adrenergic receptor

α1-Adrenergic Receptors (ARs) are G-protein Coupled Receptors (GPCRs) that regulate the sympathetic nervous system via the binding and activation of norepinephrine (NE) and epinephrine (Epi). α1-ARs control various aspects of neurotransmission, cognition, cardiovascular functions as well as other organ systems. However, therapeutic drug development for these receptors, particularly agonists, has been stagnant due to unwanted effects on blood pressure regulation. We report the synthesis and characterization of the first positive allosteric modulator (PAM) for the α1-AR based upon the derivation of the α1A-AR selective imidazoline agonist, cirazoline. Compound 3 (Cmpd-3) binds the α1A-AR with high and low affinity sites (0.13pM; 54 ​nM) typical of GPCR agonists, and reverts to a single low affinity site of 100 ​nM upon the addition of GTP. Comparison of Cmpd-3 versus other orthosteric α1A-AR-selective imidazoline ligands reveal unique properties that are consistent with a type I PAM. Cmpd-3 is both conformationally and ligand-selective for the α1A-AR subtype. In competition binding studies, Cmpd-3 potentiates NE-binding at the α1A-AR only on the high affinity state of NE with no effect on the Epi-bound α1A-AR. Moreover, Cmpd-3 demonstrates signaling-bias and potentiates the NE-mediated cAMP response of the α1A-AR at nM concentrations with no effects on the NE-mediated inositol phosphate response. There are no effects of Cmpd-3 on the signaling at the α1B- or α1D-AR subtypes. Cmpd-3 displays characteristics of a pure PAM with no intrinsic agonist properties. Specific derivation of Cmpd-3 at the R1 ortho-position recapitulated PAM characteristics. Our results characterize the first PAM for the α1-AR and holds promise for a first-in-class therapeutic to treat various diseases without the side effect of increasing blood pressure intrinsic to classical orthosteric agonists.

Histopathological evaluation of the effects of dexmedetomidine against pituitary damage ınduced by X-ray irradiation

Background: The present study, aimed to investigate the potential negative effects of x-ray radiation and the effects of the α2-adrenergic receptor agonist dexmedetomidine on the pituitary gland. Methods: Twenty-four Sprague-Dawley rats were divided into three groups: Rats in Group 1 (control group). Group 2 (X-ray irradiation) and group 3 (X-ray irradiation + Dexmedetomidine) were given a total of 10 Gy external beam total body irradiation. Group 3 was given a single intraperitoneal dose of 200 µg/kg dexmedetomidine 30 minutes before RT. Results: In sections obtained from the x-ray irradiation group, we observed many necrotic in adenohypophysis and neurohypophysis. In addition, there were extensive oedematous areas and vascular congestions due to the necrotic cells in both the adenohypophysis and neurohypophysis. In contrast, we observed a reduction in necrotic chromophobic and chromophilic cells in adenohypophyseal tissue and a reduction in necrotic pituicytes in neurohypophyseal tissue in the dexmedetomidine treatment group. In addition, we determined lower caspase-3 and TUNEL expression in the dexmedetomidine treatment group compared with the x-ray irradiation group. Dexmedetomidine reduced x-ray radiation-induced pituitary damage by preventing apoptosis. Conclusions: The present study demonstrated the use of dexmedetomidine in situations related to radiation toxicity and offers the potential for a comprehensive study.

The Effect of α2-Adrenoreceptors Blockade on the Isolated Rat Heart during the Formation of Sympathetic Innervation.

We studied the effects of the α2-adrenergic receptor antagonist yohimbine (10-9-10-6 M) on inotropy, chronotropy, and coronary flow in the Langendorff-isolated heart from 3- and 6-week-old rats. Yohimbine affected all the studied functional parameters of the isolated heart. The force of contraction of the left ventricular myocardium, HR, and coronary flow decreased at all studied concentrations of the antagonist. The maximum chronotropic effect was observed in the heart from 6-week-old rats in the presence of 10-6 M yohimbine in the perfused solution and in the heart from 3-week-old rats in the presence of 10-9 M yohimbine. The minimum chronotropic and inotropic effect was recorded in the hearts from 6-week-old animals after application of 10-9 M α2-adrenergic receptor blocker and in the hearts from 3-week-old animals at yohimbine concentration of 10-7 M. The least pronounced decrease in coronary flow in 3- and 6-week-old rats was observed at the minimum concentration of yohimbine.