Iz Shahid

Orexin A in rat rostral ventrolateral medulla is pressor, sympatho-excitatory, increases barosensitivity and attenuates the somato-sympathetic reflex.

BACKGROUND AND PURPOSE The rostral ventrolateral medulla (RVLM) maintains sympathetic nerve activity (SNA), and integrates adaptive reflexes. Orexin A‐immunoreactive neurones in the lateral hypothalamus project to the RVLM. Microinjection of orexin A into RVLM increases blood pressure and heart rate. However, the expression of orexin receptors, and effects of orexin A in the RVLM on splanchnic SNA (sSNA), respiration and adaptive reflexes are unknown.

Antinociceptive and sedative effects of the bark of Cerbera odollam Gaertn.

The crude methanolic extract of the bark of Cerbera odollam Gaertn. was evaluated for its possible antinociceptive and neuropharmacological activities in animal models. At the dose of 250 and 500 mg/kg body weight, the extract showed a significant antinociceptive effect in acetic acid induced writhing in mice comparable to that produced by aspirin, used as standard drug (P

Intrathecal orexin A increases sympathetic outflow and respiratory drive, enhances baroreflex sensitivity and blocks the somato-sympathetic reflex

BACKGROUND Intrathecal (i.t.) injection of orexin A (OX‐A) increases blood pressure and heart rate (HR), but the effects of OX‐A on sympathetic and phrenic, nerve activity, and the baroreflex(es), somato‐sympathetic and hypoxic chemoreflex(es) are unknown.

Intrathecal neuromedin U induces biphasic effects on sympathetic vasomotor tone, increases respiratory drive and attenuates sympathetic reflexes in rat.

BACKGROUND Neuromedin U (NMU) is a brain–gut peptide that plays regulatory roles in feeding, anxiety, smooth muscle contraction, blood flow, pain and adrenocortical function via two receptors, the NMU receptor 1 and NMU receptor 2. NMU has several known functions in the periphery, but its role in central cardiorespiratory regulation remains poorly understood.

Evaluation of antimicrobial, cytotoxic, thrombolytic, diuretic properties and total phenolic content of Cinnamomum tamala

Background: The leaves of Cinnamomum tamala are aromatic, carminative, stimulant, diuretic, diaphoretic, lactagogue, and deobstruent. Other parts of the plant are also used as traditional remedies for various diseases. Aim: The aim of our study was to carry out the evaluation of the preliminary phytochemical and some pharmacological properties including cytotoxicity, antibacterial and antifungal sensitivity, total phenolic content, clot lysis and diuretic potential of the leaves of C. tamala. Materials and Methods: Phytochemical screening of ethanol extract was carried out by standard chromogenic reagents and total phenolic content was estimated in term of gallic acid equivalent by using Folin Ciocalteu’s reagent. Brine shrimp lethality assay method was used to determine the degree of cytotoxicity. Antibacterial and antifungal sensitivity test was performed using disc diffusion method in agar medium and minimum inhibitory concentration was determined by micro dilution method. Clot lysis and diuretic potential were compared with streptokinase and furosemide, respectively. Statistical Analysis: The results were statistically interpreted using Student’s “ t” test. Results: The extract contained alkaloids, steroids, tannins and reducing sugars. Total phenolic content was found to be 276 gallic acid equivalent/100 g of dried plant material. In brine shrimp lethality assay, it showed moderate toxicity (LC50 = 40 μg/ml and LC90 = 160 μg/ml). The extract inhibited growth of tests bacteria and fungi with significant zones of inhibition. Highest activity was observed against the bacteria Salmonella typhi and the fungus Aspergillus niger. In‑vitro clot lysis action of extract was comparable with streptokinase (48.22 ± 2.98%) and maximum effect (24.75 ± 1.27%) was found at a dose of 10 mg/ml. The extract showed diuretic activity which responded 29.16% and 37.50% diuretic activity in comparison with control (water) which indicates the plant mild diuretic activity. Conclusion: The results depicted that traditional uses of the plant are rational, however, advanced researches are needed to identify the active components as well as mechanism of action. Key words: Antibacterial, antifungal, Cinnamomum tamala, cytotoxicity, diuretic, total phenolic content, thrombolytic

Anti-inflammatory, antinociceptive and diuretic activities of Amoora cucullata Roxb.

The crude methanolic extract of the leaves of Amoora cucullata Roxb. was investigated for its possible anti-inflammatory activity using carrageenin induced rat paw edema model and cotton pellet implantation method in rat. The extract was also studied for its antinociceptive activity using acetic acid induced writhing model in mice. At the doses of 200 and 400 mg/kg body weight, the extract showed significant anti-inflammatory activity in both models. At the same doses, the extract also significantly reduced the number of acetic acid-induced abdominal constriction (writhing) in mice. The crude extract also showed significant diuretic activity in albino mice.

Neuromedin U causes biphasic cardiovascular effects and impairs baroreflex function in rostral ventrolateral medulla of spontaneously hypertensive rat.

Neuromedin U (NMU) causes biphasic cardiovascular and sympathetic responses and attenuates adaptive reflexes in the rostral ventrolateral medulla (RVLM) and spinal cord in normotensive animal. However, the role of NMU in the pathogenesis of hypertension is unknown. The effect of NMU on baseline cardiorespiratory variables in the RVLM and spinal cord were investigated in urethane-anaesthetized, vagotomized and artificially ventilated male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Experiments were also conducted to determine the effects of NMU on somatosympathetic and baroreceptor reflexes in the RVLM of SHR and WKY. NMU injected into the RVLM and spinal cord elicited biphasic response, a brief pressor and sympathoexcitatory response followed by a prolonged depressor and sympathoinhibitory response in both hypertensive and normotensive rat models. The pressor, sympathoexcitatory and sympathoinhibitory responses evoked by NMU were exaggerated in SHR. Phrenic nerve amplitude was also increased following intrathecal or microinjection of NMU into the RVLM of both strains. NMU injection into the RVLM attenuated the somatosympathetic reflex in both SHR and WKY. Baroreflex sensitivity was impaired in SHR at baseline and further impaired following NMU injection into the RVLM. NMU did not affect baroreflex activity in WKY. The present study provides functional evidence that NMU can have an important effect on the cardiovascular and reflex responses that are integrated in the RVLM and spinal cord. A role for NMU in the development and maintenance of essential hypertension remains to be determined.

Differential cardiorespiratory and sympathetic reflex responses to microinjection of neuromedin U in rat rostral ventrolateral medulla

The rostral ventrolateral medulla (RVLM) regulates sympathetic vasomotor outflow and reflexes. Intracerebroventricular neuromedin U (NMU) increases sympathetic nerve activity (SNA), mean arterial pressure (MAP), and heart rate (HR), but the central nuclei that mediate these effects are unknown. In urethane-anesthetized, vagotomized, and artificially ventilated male Sprague-Dawley rats (n = 36) the effects of bilateral microinjection of NMU (50 nl, each side) into RVLM on cardiorespiratory variables, somatosympathetic reflex, arterial baroreflex, and chemoreflex were investigated. Microinjection of NMU into RVLM elicited a hypertension, tachycardia, and an increase in splanchnic SNA (SSNA) and lumbar SNA (LSNA) at lower doses (25 and 50 pmol). At higher dose (100 pmol), NMU caused a biphasic response, a brief hypertension and sympathoexcitation followed by prolonged hypotension and sympathoinhibition. The peak excitatory and inhibitory response was found at 100 pmol NMU with an increase in MAP, HR, SSNA, and LSNA of 36 mm Hg, 20 beats per minute, 34%, and 89%, respectively, and a decrease of 33 mm Hg, 25 beats per minute, 42%, and 52%, respectively, from baseline. NMU, in the RVLM, also increased phrenic nerve amplitude and the expiratory period and reduced the inspiratory period. NMU (100 pmol) attenuated the somatosympathetic reflex and the sympathoexcitatory and respiratory responses to hypoxia and hypercapnia. After NMU injection in RVLM, the maximum gain of the SSNA baroreflex function curve was increased, but that of the LSNA was reduced. The present study provides functional evidence for a complex differential modulatory activity of NMU on the cardiovascular and reflex responses that are integrated in the RVLM.

Vasostatin I (CgA17-76) vasoconstricts rat splanchnic vascular bed but does not affect central cardiovascular function.

Vasostatin I (CgA(1-76)) is a naturally occurring biologically active peptide derived from chromogranin A (CgA), and is so named for its inhibitory effects on vascular tension. CgA mRNA is expressed abundantly in sympathoexcitatory catecholaminergic neurons of the rostral ventrolateral medulla (RVLM). CgA microinjection into the RVLM decreases blood pressure (BP), heart rate (HR) and sympathetic nerve activity (SNA). Proteolytic fragments of CgA are thought to be responsible for the cardiovascular effects observed. We hypothesised that vasostatin I is one of the fragments responsible for the central effects of CgA. We examined the role of a vasostatin I fragment, CgA(17-76) (VS-I((CgA17-76))), containing the portion important for biological effects. The effects of VS-I((CgA17-76)) delivered by intrathecal injection, or microinjection into the RVLM, on cardio-respiratory function in urethane anaesthetised, vagotomised, mechanically ventilated Sprague-Dawley rats (n=21) were evaluated. The effects of intrathecal VS-I((CgA17-76)) on the somato-sympathetic, baroreceptor and peripheral chemoreceptor reflexes were also examined. At the concentrations used (10, 100 or 200 μM, intrathecal; or 5 μM, RVLM microinjection) VS-I((CgA17-76)) produced no change in mean arterial pressure, HR, splanchnic SNA, phrenic nerve amplitude or phrenic nerve frequency. All reflexes examined were unchanged following intrathecal VS-I((CgA17-76)). In the periphery, VS-I((CgA17-76)) potentiated the contractile effects of noradrenaline on rat mesenteric arteries (n=6), with a significant left-shift in the dose response curve to noradrenaline (3.7×10(-7) vs 7.7×10(-7)). Our results indicate that VS-I((CgA17-76)) is active in the periphery but not centrally, and is not a central modulator of cardiorespiratory function and physiological reflexes.

Free radical scavenging activity of some Mangroves available in Bangladesh

The crude alcoholic extracts of various parts of five different Bangladeshi mangrove plants (Amoora cucullata, Caesalpinia bonducella, Cerbera odollam, Derris uliginosa and Sonneratia caseolaris) were screened in-vitro for anti-oxidant activity using the 1,1-diphenyl-2-picryldydrazyl-hydrate (DPPH) free radical scavenging assay. Of all of them, the ethanolic extracts of the leaves of Derris uliginosa and Sonneratia caseolaris showed potential antioxidant activity (: 94.406 and 26.30 mg/ml respectively) whereas the ethanolic extracts of aerial parts of Derris uliginosa, barks of Cerbera odollam and leaves and stems of Caesalpinia bonducella showed moderate activity (: 125.89, 211.35 and 301.99 mg/ml respectively). Mild anti-oxidant activity was observed with the methanolic extract of leaves of Amoora cucullata and ethanolic extracts of fruits of Cerbera odollam.