Browsing by Author "Ravindran Revand"

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Algogen-induced vasosensory reflexes modulate short-term heart rate variability parameters in experimental rat models
(De Gruyter Open Ltd, 2022) Ravindran Revand; Sanjeev K. Singh
Objectives: The present work was designed to study the modulatory effects of algogen-induced vasosensory reflex responses on short-term heart rate variability (HRV) parameters in naïve and vagotomized rat models. Methods: In this study, vasosensory reflex responses were elicited by instilling algogens (bradykinin/histamine), a component of inflammatory mediators into a local segment of medium-sized peripheral blood vessel (femoral artery) while a continuous electrocardiogram (ECG) was recorded. Short-term (5 min) ECG segments obtained from original recordings were examined in detail and relevant data of HRV parameters were pooled. Time domain and frequency domain analyses were performed using dedicated software (LabChart 8, AD Instruments®, Australia) and results were analyzed. Results: Bradykinin-induced vasosensory reflexes caused significant alterations in both time domain and frequency domain HRV parameters as compared to the time-matched saline control group. Instillation of bradykinin caused a transient increase in NN interval, RMSSD, TSP, HF power (HFP) along with a decrease in the standard deviation of all normal NN intervals (SDNN), SDNN/RMSSD, LF power (LFP), LFP/HFP. Histamine produced a similar pattern of responses, but HRV alterations were less pronounced compared to those with bradykinin. Further analysis revealed that algogen-induced vasosensory reflex responses caused an increase in the parasympathetic influence on the heart accompanied by a decrease in sympathetic influence. In addition, HRV modulation by algogen-induced vasosensory reflexes was significantly attenuated in vagotomized rats, illustrating the principal role of vagus in the reflex HRV modulation. Conclusions: The present study proposes a novel hypothesis regarding the cardio-protective role of inflammatory mediators during acute stress, by potentiating the vagal impact and attenuating the sympathetic impact on the heart. © 2021 Walter de Gruyter GmbH, Berlin/Boston.
GPIIb/IIIa Receptor Targeted Rutin Loaded Liposomes for Site-Specific Antithrombotic Effect
(American Chemical Society, 2023) Vishnu Priya; Sanjeev K. Singh; Ravindran Revand; Sandip Kumar; Abhishesh Kumar Mehata; Paulraj Sushmitha; Sanjeev Kumar Mahto; Madaswamy S. Muthu
Rutin (RUT) is a flavonoid obtained from a natural source and is reported for antithrombotic potential, but its delivery remains challenging because of its poor solubility and bioavailability. In this research, we have fabricated novel rutin loaded liposomes (RUT-LIPO, nontargeted), liposomes conjugated with RGD peptide (RGD-RUT-LIPO, targeted), and abciximab (ABX-RUT-LIPO, targeted) by ethanol injection method. The particle size, ζ potential, and morphology of prepared liposomes were analyzed by using DLS, SEM, and TEM techniques. The conjugation of targeting moiety on the surface of targeted liposomes was confirmed by XPS analysis and Bradford assay. In vitro assessment such as blood clot assay, aPTT assay, PT assay, and platelet aggregation analysis was performed using human blood which showed the superior antithrombotic potential of ABX-RUT-LIPO and RGD-RUT-LIPO liposomes. The clot targeting efficiency was evaluated by in vitro imaging and confocal laser scanning microscopy. A significant (P < 0.05) rise in the affinity of targeted liposomes toward activated platelets was demonstrated that revealed their remarkable potential in inhibiting thrombus formation. Furthermore, an in vivo study executed on Sprague Dawley rats (FeCl3model) demonstrated improved antithrombotic activity of RGD-RUT-LIPO and ABX-RUT-LIPO compared with pure drug. The pharmacokinetic study performed on rats demonstrates the increase in bioavailability when administered as liposomal formulation as compared to RUT. Moreover, the tail bleeding assay and clotting time study (Swiss Albino mice) indicated a better antithrombotic efficacy of targeted liposomes than control preparations. Additionally, biocompatibility of liposomal formulations was determined by an in vitro hemolysis study and cytotoxicity assay, which showed that they were hemocompatible and safe for human use. A histopathology study on rats suggested no severe toxicity of prepared liposomal formulations. Thus, RUT encapsulated nontargeted and targeted liposomes exhibited superior antithrombotic potential over RUT and could be used as a promising carrier for future use. © 2023 American Chemical Society. All rights reserved.
Intra-arterial instillation of a nociceptive agent modulates cardiorespira-tory parameters involving 5-ht3 and trpv1 receptors in anesthetized rats
(Bentham Science Publishers, 2021) Sanjeev K. Singh; M.S. Muthu; Ravindran Revand; Maloy B. Mandal
Background: Since long back, it has been a matter of discussion regarding the role of peripheral blood vessels in the regulation of cardiorespiratory (CVR) system. Objective: The role of 5-HT3 and TRPV1 receptors present on perivascular nerves in elicitation of CVR reflexes was examined after intra-arterial instillation of bradykinin in urethane anesthetized rats. Materials and Methods: Femoral artery was cannulated retrogradely and was utilized for the instil-lation of saline/agonist/antagonist and recording of blood pressure (BP), using a double ported 24G cannula. BP, respiration and ECG were recorded for 30 min after bradykinin (1 μM) in the absence or presence of antagonists. Results: Instillation of bradykinin produced immediate hypotensive (40%), bradycardiac (17%), tachypnoeic (45%) and hyperventilatory (96%) responses of shorter latencies (5-8 s) favoring the neural mechanisms in producing the responses. In lignocaine (2%) pretreated animals, bradykin-in-induced hypotensive (10%), bradycardiac (1.7%), tachypnoeic (13%) and hyperventilatory (13%) responses attenuated significantly. Pretreatment with ondansetron (100 μg/kg), 5-HT3-antag-onist attenuated the hypotensive (10%), bradycardiac (1.7%), tachypnoeic (11%) and hyperventila-tory (11%) responses significantly. Pretreatment with capsazepine (1 mg/kg), transient receptor potential vanilloid 1-antagonist blocked the hypotensive (5%), bradycardiac (1.2%), tachypnoeic (6%) and hyperventilatory (6%) responses significantly. Conclusion: In conclusion, presence of a nociceptive agent in the local segment of an artery evokes vasosensory reflex responses modulating CVR parameters involving TRPV1 and 5-HT3 receptors present on the perivascular sensory nerve terminals in anesthetized rats. © 2021 Bentham Science Publishers.
Ipsilateral somatic nerves mediate histamine-induced vasosensory reflex responses involving perivascular afferents in rat models
(Nature Research, 2021) Ravindran Revand; Sanjeev K. Singh
Reflex cardiorespiratory alterations elicited after instillation of nociceptive agents intra-arterially (i.a) are termed as ‘vasosensory reflex responses’. The present study was designed to evaluate such responses produced after i.a. instillation of histamine (1 mM; 10 mM; 100 mM) and to delineate the pathways i.e. the afferents and efferents mediating these responses. Blood pressure, electrocardiogram and respiratory excursions were recorded before and after injecting saline/histamine, in a local segment of femoral artery in urethane anesthetized rats. Paw edema and latencies of responses were also estimated. Separate groups of experiments were conducted to demonstrate the involvement of somatic nerves in mediating histamine-induced responses after ipsilateral femoral and sciatic nerve sectioning (+NX) and lignocaine pre-treatment (+Ligno). In addition, another set of experiments was performed after bilateral vagotomy (+VagX) and the responses after histamine instillation were studied. Histamine produced concentration-dependent hypotensive, bradycardiac, tachypnoeic and hyperventilatory responses of shorter latencies (2–7 s) favouring the neural mechanisms in eliciting the responses. Instillation of saline (time matched control) in a similar fashion produced no response, excluding the possibilities of ischemic/stretch effects. Paw edema was absent in both hind limbs indicating that the histamine did not reach the paws and did not spill out into the systemic circulation. +NX, +VagX, +Ligno attenuated histamine-induced cardiorespiratory responses significantly. These observations conclude that instillation of 10 mM of histamine produces optimal vasosensory reflex responses originating from the local vascular bed; afferents and efferents of which are mostly located in ipsilateral somatic and vagus nerves respectively. © 2021, The Author(s).
Perivascular histamine receptors mediate vasosensory reflex responses elicited by thermal nociceptive stimuli in anaesthetised rat models
(Scientific Scholar, 2021) Ravindran Revand; Sanjeev K. Singh
Objectives: Reflex responses elicited by intra-arterial (i.a) instillation of nociceptive agents are known as vasosensory reflex responses. The present study was designed to demonstrate the vasosensory reflex responses evoked by thermal nociceptive stimuli in anaesthetised rat models and to examine the role of perivascular histamine receptors in mediating these responses. Materials and Methods: In this study, saline at different temperatures (0°C/30°C/55°C) was instilled retrogradely into the femoral artery to stimulate the perivascular nociceptive terminals and the respiratory movements, BP and ECG were recorded for 10 min. Experiments were performed in four groups of rats. Two groups were dedicated to study the temperature-induced reflex cardiorespiratory (CVR) responses after i.a instillation of cold (0°C) and warm saline (55°C). The responses in these groups were compared with the responses after instillation of normal saline at room temperature (30°C) in a separate group of rats that served as time matched control group. Another group of rats was pre-treated with pheniramine and the responses elicited by warm saline were studied. Results: Instillation of warm saline produced immediate (2–6 s) hyperventilatory, hypotensive and bradycardiac responses which were short-lived, while equivolume of normal saline at room temperature did not. Cold saline also elicited the CVR changes of similar quality as that of warm saline but of lesser quantity which were not significantly different from the control group. Pre-treatment with pheniramine significantly attenuated the warm saline-induced reflex responses. Conclusion: Activation of perivascular sensory nerve terminals by thermal nociceptive stimuli elicits vasosensory reflex responses altering CVR parameters. Perivascular histamine receptors play a significant role in mediating the temperature-induced vasosensory reflex responses. ©2021 Published by Scientific Scholar on behalf of Indian Journal of Physiology and Pharmacology
Physiological Basis of Lower Limb Edema
(Springer Nature, 2022) Sanjeev K. Singh; Ravindran Revand
Edema can be defined as the accumulation of excess fluid in the interstitial or intercellular spaces of the body. Edema is usually caused due to disturbances in the mechanisms that govern exchange of water and solutes between the intravascular and the interstitial fluid compartments, at the capillary microcirculation level. The capillary blood flow and fluid exchange are compactly regulated by intrinsic and extrinsic apparatuses like capillary endothelial substances and autonomic innervations, respectively. The Starling forces, namely hydrostatic and osmotic pressure, play fundamental role in determining the fluid movements across the capillary wall. Increased capillary hydrostatic pressure or increased interstitial osmotic pressure favors outward fluid shift from capillaries-a process named filtration, while decreased capillary hydrostatic pressure or decreased interstitial osmotic pressure favors absorption, where fluid moves into the capillaries. Prolonged standing, reduced physical activity, consumption of low protein diet, pregnancy, and rapid ascent to high altitudes are some of the physiological causes of peripheral edema. On the other hand, endocrine disorders like myxedema, Cushing syndrome, and failure of vital organs like the heart, liver, and kidneys contribute to the systemic pathological etiologies of edema formation. Localized limb pathologies like lymphatic obstruction, deep vein thrombosis, dermatitis, and lipedema should also be kept in mind while discussing the causes of peripheral edema. Drugs like calcium channel blockers, corticosteroids, estrogens, progesterones, and vasodilators like minoxidil and hydralazine are known to cause peripheral edema as one of their adverse effects. A thorough history and relevant physical examination supplemented with laboratory and radiological investigations constitute the cornerstone in the diagnosis and management of patients presenting with lower limb edema in a clinical setting. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022.
Retrograde cannulation of femoral artery: A novel experimental design for precise elicitation of vasosensory reflexes in anesthetized rats
(Elsevier B.V., 2020) Ravindran Revand; Sanjeev K. Singh
Vasosensory reflex responses are elicited by instillation of nociceptive agents in a segment of peripheral blood vessel. A novel method for the stimulation of perivascular afferents was designed by retrograde cannulation of femoral artery, using a 24G, double ported polyethylene cannula. The vertical port of which was used to inject the algogen into the artery and horizontal port to measure the BP continuously, as this port was connected to the pressure transducer. Previously, separate carotid artery cannulation was used for the BP recording. But our experimental design excluded the need for carotid artery cannulation that might compromise the circulation to the CNS centers mediating cardiorespiratory reflex responses. After cannulation, the proximal end of femoral artery became an end artery and the drugs were instilled retrogradely. The volume of chemicals was kept minimal (100 µl) and the ipsilateral femoral vein was also ligated. These measures made sure that the instilled drug remained in a local segment of femoral artery and did not spill out to the systemic circulation. Further, there was no increase in the water content of ipsilateral paw as compared to the contralateral paw. This finding also substantiates our proposition regarding minimal systemic spillage. • The femoral artery is cannulated by a double ported cannula. • This cannula helps instillation of algogen and BP measurement simultaneously. • Retrograde instillation helps to deposit the algogen in a local segment of femoral artery. © 2020
Subthreshold Doses of Inflammatory Mediators potentiate One Another to Elicit Reflex Cardiorespiratory Responses in Anesthetized Rats
(Bentham Science Publishers, 2024) Ravindran Revand; Sanjeev K. Singh; Madaswamy S. Muthu
Background: Reflex cardio-vascular and respiratory (CVR) alterations evoked by intra-arterial instillation of nociceptive agents are termed vasosensory reflexes. Such responses elicited by optimal doses of inflammatory mediators have been described in our earlier work. Objective: The present study was designed to evaluate the interactions between subthreshold doses of inflammatory mediators on perivascular nociceptive afferents in urethane anesthetized rats. Methods: Healthy male adult rats (Charles-Foster strain) were anesthetized with an intraperitoneal injection of urethane. After anesthesia, the right femoral artery was cannulated. Respiratory movements, blood pressure, and electrocardiogram were recorded. The interactions between sub-threshold doses of algogens in the elicitation of vasosensory reflex responses were studied by in-stillation of bradykinin (1 nM) and histamine (100 µM) into the femoral artery one after the other, in either temporal combination in separate groups of rats. The CVR responses obtained in these groups were then compared with the responses produced by 100 µM histamine and 1 nM brady-kinin in saline-pretreated groups, which served as control. Results: Subthreshold doses of histamine elicited transient tachypnoeic, hyperventilatory, hypo-tensive, and bradycardiac responses, in rats pretreated with subthreshold doses of bradykinin [p < 0.01, two-sided Dunnett’s test] but not in saline pretreated groups [p > 0.05, two-sided Dunnett’s test]. Similar responses were elicited by bradykinin after histamine pretreatment compared to the saline-pretreated group. Furthermore, CVR responses produced by histamine in the bradykinin-pretreated group were greater in magnitude as compared to bradykinin-induced responses in the histamine-pretreated group [p < 0.05, two-sided Dunnett’s test]. Conclusion: The present study demonstrates that both bradykinin and histamine potentiate one another in the elicitation of vasosensory reflex responses, and bradykinin is a better potentiator than histamine at the level of perivascular nociceptive afferents in producing reflex CVR changes. © 2024 Bentham Science Publishers.