Pharmacological characterization of the presynaptic activity of tityus serrulatus venom in the rat anococcygeus muscle

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOScorpion venoms are known to cause peripheral nerve stimulation with enhanced autonomic responses. This study, therefore, examined the effects of Tityus serrulatus venom (TSV) on adrenergic, cholinergic and nitrergic nerve fibers using the rat anococcygeus muscle. The contractile effects of TSV (1 mug/ml) and electrical field stimulation were markedly reduced by phentolamine (5 muM), prazosin (0.1 muM), guanethidine (30 muM) and tetrodotoxin (TTX, l muM), whereas imipramine (3 muM) enhanced these responses. The responses to tyramine (10 muM) were partially reduced by guanethidine and completely blocked by phentolamine, prazosin and imipramine. Atropine (1 muM) fully prevented carbachol (CCh, 30 muM)-induced contractions without affecting those mediated by TSV. Neostigmine significantly potentiated TSV-and ACh-evoked contractions, whereas hexamethonium had no effect. The relaxant responses induced by EFS and TSV (3 mug/ml) were completely blocked by L-NAME (100 muM), ODQ (1 muM) or TTX (1 muM). Addition of L-arginine (1 mM) reversed the effect of L-NAME. Thus, the motor and inhibitory responses of TSV in the rat anococcygeus muscle are mediated by prejunctional mechanisms dependent on Na+ channel activation, causing the stimulation of NA and NO release from adrenergic and nitrergic nerve fibers, respectively425451460FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçã

Vascular effects of long-term propranolol administration after chronic nitric oxide blockade

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOLong-term propranolol treatment reduces arterial blood pressure in hypertensive individuals mainly by reducing peripheral vascular resistance, but mechanisms underlying their vasodilatory effect remain poorly investigated. This study aimed to investigate whether long-term propranolol administration ameliorates the impairment of relaxing responses of aorta and mesenteric artery from rats made hypertensive by chronic nitric oxide (NO) deficiency, and underlying mechanisms mediating this phenomenon. Male Wistar rats were treated with N-omega-Nitro-L-arginine methyl ester (L-NAME; 20 mg/rat/day) for four weeks. DL-Propranolol (30 mg/rat/day) was given concomitantly to L-NAME in the drinking water. Treatment with L-NAME markedly increased blood pressure, an effect largely attenuated by DL-propranolol. In phenylephrine-precontracted aortic rings, the reduction of relaxing responses for acetylcholine (0.001-10 mu M) in L-NAME group was not modified by DL-propranolol, whereas in mesenteric rings the impairment of acetylcholine-induced relaxation by L-NAME was significantly attenuated by DL-propranolol. In mesenteric rings precontracted with KCl (80 MM), DL-propranolol failed to attenuate the impairment of acetylcholine-induced relaxation by L-NAME. The contractile responses to extracellular CaCl2 (1-10 mM) were increased in L-NAME group, and co-treatment with DL-propranolol reduced this response in both preparations in most Ca2+ concentrations used. The NO2/NO3 plasma levels and superoxide dismutase (SOD) activity were reduced in L-NAME-treated rats, both of which were significantly prevented by DL-propranolol. In conclusion, propranolol-induced amplification of the relaxation to acetylcholine in mesenteric arteries from L-NAME-treated rats is sensitive to depolarization. Additional mechanisms involving blockade of Ca2+ entry in the vascular smooth muscle and increase in NO bioavailability contributes to beneficial effects of long-term propranolol treatmentElsevier5712-3189196FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçãoAmsterd

Superoxide anion production by NADPH oxidase plays a major role in erectile dysfunction in middle-aged rats: prevention by antioxidant therapy

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOPrevalence of erectile dysfunction (ED) increases progressively with aging, but the ED pathophysiology at its early stages is still poorly investigated. Aim. This study aimed to evaluate the functional and molecular alterations of erectile function at middle age, focusing on the contribution of oxidative stress in erectile tissue for the ED. Methods. Young (3.5-month) and middle-aged (10-month) male Wistar rats were used. Rat corpus cavernosum (RCC) was dissected free and mounted in 10-mL organ baths containing Krebs solution. Intracavernosal pressure (ICP) in anesthetized rats was evaluated. Main Outcome Measures. Concentrationresponse curves to endothelium-dependent and endothelium-independent agents, as well as to electrical field stimulation (EFS), were obtained in RCC strips. Measurement of cyclic guanosine monophosphate (cGMP) and expressions of neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS), gp91phox and superoxide dismutase-1 (SOD-1) expressions in RCC were evaluated. Results. ICP was significantly reduced in middle-aged compared with young rats. RCC relaxations to acetylcholine (108 to 102M), sodium nitroprusside (108 to 102M), sildenafil (109 to 105M), BAY 41-2272 (109 to 105M), and EFS (432Hz) were decreased in middle-aged group, which were nearly normalized by apocynin (NADPH oxidase inhibitor; 104M) or SOD (75U/mL). Prolonged treatment with apocynin (85mg/rat/day, 4 weeks) also restored the impaired relaxations in middle-aged rats. Relaxations to 8-bromoguanosine 3,5-cyclic monophosphate sodium salt (8-Br-cGMP; 108 to 3x104M) remained unchanged between groups. Basal and stimulated cGMP production were lower in middle-aged group, an effect fully restored by apocynin and SOD. Protein expression of nNOS and phosphorylated eNOS (p-eNOS) (Ser-1177) reduced, whereas gp91phox mRNA expression increased in RCC from middle-aged rats. Conclusions. ED in middle-aged rats is associated with decreased NO bioavailability in erectile tissue due to upregulation of NADPH oxidase subunit gp91phox and downregulation of nNOS/p-eNOS. Antioxidant therapies may be a good pharmacological approach to prevent ED at its early stages. Silva FH, Monica FZ, Bau FR, Brugnerotto AF, Priviero FBM, Toque HA, and Antunes E. Superoxide anion production by NADPH oxidase plays a major role in erectile dysfunction in middle-aged rats: Prevention by antioxidant therapy104960971FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçã

Vasorelaxing effects of propranolol in rat aorta and mesenteric artery: a role for nitric oxide and calcium entry blockade

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOPropranolol has been prescribed successfully to patients with cardiovascular diseases, but the exact mechanisms by which it reduces peripheral vascular resistance have been poorly investigated. 2. The present study was designed to investigate the relaxing effects of propranolol in the rat isolated aorta and mesenteric artery, focusing on the contribution of the nitric oxide (NO)-cGMP pathway and calcium entry blockade. Relaxation responses to propranolol were obtained in precontracted rat aortic and mesenteric artery rings. 3. DL-Propranolol (10-100 mu mol/L) produced concentration-dependent relaxations in the aorta and mesenteric artery rings with intact endothelium. The isomers D- and L-propranolol produced relaxation responses that were equipotent to the racemic mixture. 4. Metoprolol (10-100 mu mol/L) produced slight relaxations, whereas atenolol (10-100 mu mol/L) had no relaxant activity. 5. The NO inhibitor N-G-nitro-L-arginine methyl ester (100 mu mol/L) and the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (1 mu mol/L), as well as removal of the endothelium, significantly reduced the relaxation responses induced by the lower concentrations of propranolol without affecting maximal responses. In addition, DL-propranolol markedly increased cGMP levels in endothelium-intact preparations. 6. In Ca2+-free Krebs' solution, DL-propranolol (10-100 mu mol/L) caused marked rightward shift in the concentration-response curves to CaCl2, with a decrease of maximal responses in tissues with either intact or denuded endothelium. Nifedipine (1 mu mol/L) in combination with DL-propranolol virtually abolished the CaCl2-induced contractile responses. 7. The relaxation responses induced by DL-propranolol were significantly reduced in aortic and mesenteric rings precontracted with phorbol-12,13-dibutyrate (1 mu mol/L). 8. In conclusion, DL-propranolol relaxes arterial smooth muscle by mechanisms involving activation of the NO-cGMP pathway and calcium influx blockade, independent of beta-adrenoceptor blockade335-6448455FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçã

Chronotropic Response Of β-adrenergic-, Muscarinic-, And Calcitonin Gene-related Peptide-receptor Agonists In Right Atria From Neonatal Capsaicin-treated Rats

We evaluated the potency of isoproterenol, carbachol, pilocarpine and calcitonin gene-related peptide (CGRP) in the rat right atria at 30, 60 and 90 days after neonatal capsaicin treatment. Neonatal rats were pretreated on the second day of life with capsaicin (50 mg/kg). The capsaicin pretreatment caused a five-fold rightward shift at the pEC50 level on the concentration-response curves to isoproterenol in 30-day-old rats. Propranolol (10 mg/kg, given 15 min prior to capsaicin treatment) prevented this subsensitivity. No changes in the potency of isoproterenol were observed at 60 and 90 days after capsaicin pretreatment. The potency and maximal responses of CGRP in the right atria in 30-day-old rats were significantly higher than in 60- and 90-day-old rats; however, no differences were found between control and capsaicin groups. The potency and maximal responses to carbachol and pilocarpine were not changed in all groups. The neonatal capsaicin treatment reduced by about 74% the CGRP content in the heart in all groups. In summary, capsaicin treatment in newborn rats produces a desensitization of chronotropic response mediated by β-adrenoceptors in isolated right atria from 30-day-old rats possibly due to a massive release of catecholamines. © 2002 Elsevier Science Ireland Ltd. All rights reserved.3253147150Alving, K., Matran, R., Lundberg, J.M., Capsaicin-induced local effector responses, autonomic reflexes and sensory neuropeptide depletion in the pig (1991) Naunyn-Schmiedeberg's Arch. Pharmacol., 343, pp. 37-45Amerini, S., Rubino, A., Mantelli, L., Ledda, F., α-Adrenoceptor modulation of the efferent function of capsaicin-sensitive sensory neurones in guinea-pig isolated atria (1992) Br. J. Pharmacol., 105, pp. 947-953Armour, J.A., Yuan, B.X., Butler, C.K., Cardiac responses elicited by peptides administered to canine intrinsic cardiac neurons (1990) Peptides, 11, pp. 753-761Bonish, H., Further studies on the extraneuronal uptake and metabolism of isoprenaline in the perfused rat heart (1978) Naunyn-Schmiedeberg's Arch. Pharmacol., 303, pp. 121-131Hoover, D.B., Effects of substance P on rate and perfusion pressure in the isolated guinea pig heart (1989) J. Pharmacol. Exp. Ther., 252, pp. 179-184Jancsó, N., Kiraly, E., Jancsó-Gabor, A., Pharmacologically induced selective degeneration of chemosensitive primary sensory neurons (1977) Nature, 270, pp. 741-743Jancsó, N., Kiraly, E., Joo, F., Such, G., Nagy, A., Selective degeneration by capsaicin of a subpopulation of primary sensory neurons in the adult rat (1985) Neurosci. Lett., 59, pp. 209-214Marfurt, C.F., Ellis, L.C., Jones, M.A., Sensory and sympathetic nerve sprouting in the rat cornea following neonatal administration of capsaicin (1993) Somatosensory Motor Res., 10, pp. 377-398Miyake, H., Inaba, N., Kato, S., Takeuchi, K., Increased susceptibility of rat gastric mucosa to ulcerogenic stimulation with aging. Role of capsaicin-sensitive sensory neurons (1996) Dig. Dis. Sci., 41, pp. 339-345Rubino, A., Burnstock, G., Capsaicin-sensitive sensory-motor nerves in the control of cardiovascular function (1996) Cardiovasc. Res., 31, pp. 467-479Rubino, A., Ralevic, V., Burnstock, G., Sympathetic neurotransmission in isolated rat atria after sensory-motor denervation by neonatal treatment with capsaicin (1997) J. Pharmacol. Exp. Ther., 282, pp. 671-675Seyedi, N., Maruyama, R., Levi, R., Bradykinin activates a cross-signaling pathway between sensory and adrenergic nerve endings in the heart: A novel mechanism of ischemic norepinephrine release? (1999) J. Pharmacol. Exp. Ther., 290, pp. 656-663Simone, D.A., Nolano, M., Johnson, T., Wendelschafer-Crabb, G., Kennedy, W.R., Intradermal injection of capsaicin in humans produces degeneration and subsequent reinnervation of epidermal nerve fibers: Correlation with sensory function (1998) J. Neurosci., 18, pp. 8947-8959Stiles, G.L., Caron, M.G., Lefkowitz, R.J., Beta-adrenergic receptors: Biochemical mechanisms of physiological regulation (1984) Physiol. Rev., 64, pp. 661-743Szallasi, A., Blumberg, P.M., Vanilloid (capsaicin) receptors and mechanisms (1999) Pharmacol. Rev., 51, pp. 159-211Zanesco, A., Costa, S.K.P., Riado, S.R., Nathan, L.P., Oliveira, C.F., De Luca, I.M.S., Antunes, E., De Nucci, G., Modulation of coronary flow and cardiomyocytes size by sensory fibers (1999) Hypertension, 34, pp. 790-79

Nitric oxide release from human corpus cavernosum induced by a purified scorpion toxin

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOTo investigate the effects of a purified scorpion toxin (Ts3) on human corpus cavernosum (HCC) in vitro. Scorpion venoms cause a massive release of neurotransmitters that contribute to the clinical symptoms resulting from envenomation. Methods. HCC strips were mounted in organ baths containing Krebs solution. After equilibration, the tissues were precontracted with phenylephrine (10 mumol/L). The relaxations caused by Ts3 (30 nmol/L) were compared with those induced by electrical field stimulation (1 to 20 Hz) and nitric oxide (NO, 1 to 100 mumol/L). Results. The addition of Ts3 evoked long-lasting relaxations of precontracted HCC strips, and exogenously applied NO and electrical field stimulation caused short-lived responses. The NO synthesis inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME; 100 mumol/L) reduced by 87% +/- 2% the Ts3-induced relaxations; this inhibition was reversed by pretreating the tissues with L-arginine (1 mmol/L). The relaxant responses mediated by Ts3 were blocked to a similar degree by the soluble guanylyl cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3,-alquinoxalin-1-one] (10 mumol/L). In contrast, the addition of the phosphodiesterase type 5 inhibitor sildenafil (0.1 mumol/L) significantly enhanced Ts3-evoked relaxations by 78% +/- 4%. The sodium channel blocker tetrodotoxin (1 mumol/L) completely blocked the relaxant responses elicited by both Ts3 and electrical field stimulation, without significantly affecting those elicited by NO. Conclusions. The results indicate that Ts3 relaxes the HCC through the release of NO from nitrergic nerves. The elucidation of this mechanism is useful for the development of new therapeutic strategies to treat priapism after scorpion envenomation or to modulate sodium channel activity in the case of penile dysfunction631184189FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçã

Progression of micturition dysfunction associated with the development of heart failure in rats : model of overactive bladder

Heart failure (HF) has a strong association with the development of lower urinary tract symptoms, especially overactive bladder (OAB); although this condition remains poorly investigated. In this study, we assess the aortocaval fistula (ACF) model as a novel experimental model of micturition dysfunction, associated with HF, focused on the molecular and functional studies to evaluate the autonomic nervous system and urinary bladder remodeling. Male rats were submitted to ACF for HF induction. Echocardiography, cystometric, histomorphometry and molecular analysis, as well as concentration-response curves to carbachol and ATP and frequency-response curves to electrical field stimulation (EFS) were evaluated in Sham and HF (4- and 12-weeksendpoint) groups. Compared to SHAM, HF groups exhibited progressive increases in the left ventricle (LV) mass and fractional shortening which indicates cardiac dysfunction, although HF was characterized only after 12 weeks by the reduced ejection fraction. For micturition function, HF groups presented increased non-voiding contractions (NVC) and decreased bladder capacity; however, when comparing HF groups, these urinary parameters were significantly impaired over the weeks (12-weeks). The contractile responses induced by CCh, ATP and EFS were greater in detrusor muscle (DSM) from HF rats. mRNA expression for muscarinic receptors (M2 and M3) was higher in DSM only after 12 weeks of ACF, in addition to MMP9 and TGF-beta. Histomorphometric revealed increased urothelium thickness in both HF groups, whereas DSM thickness occurred only after 12 weeks. Thus, the ACF model induced cardiac dyfunction with progressive micturition dysfunction over the weeks, characterized by increased DSM contractile mechanisms as well as extracellular matrix remodeling in the urinary bladder, representing a useful tool to evaluate the OAB associated with HF226107116FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2011/21095-