1. Compared with the effects of adenosine 5' triphosphate (ATP) on the nervous system, the actions of pyrimidine nucleosides and their 5'-nucleotides, such as uridine 5' triphosphate (UTP), have received less attention. In part, this is because there is a need for a selective antagonist for responses mediated by UTP-activated receptors. The objective of this study was to discover such an antagonist. 2. Superior cervical ganglia isolated from male rats were superfused with a physiological salt solution. Responses to alpha,beta-methylene-ATP (alpha,beta-Me-ATP), potassium, adenosine and UTP were determined before and in the presence of 1-300 microM methyl orange. 3. Methyl orange at 1-100 microM did not alter resting potential or depolarizing responses to alpha,beta-Me-ATP, potassium, or adenosine-evoked hyperpolarizations, but at 10 and 100 microM methyl orange significantly antagonized UTP-evoked depolarizations (P < 0.05). 4. Although the antagonistic effects of methyl orange were not dramatic, this is the first report of a putative pyrimidinoceptor antagonist. These observations also support the idea of distinct receptors for UTP and ATP on rat superior cervical ganglia.
1. We have examined the effects of 17beta-oestradiol on spontaneous spikes and contractions to noradrenaline in rat portal vein. 2. The 17beta-oestradiol (10 microM) significantly reduced the maximum height of spontaneous spike contractions and significantly reduced the maximum contraction to noradrenaline (10 microM) in portal vein from both male and female rats. 3. The protein synthesis inhibitor cycloheximide (10 microM) did not significantly affect the inhibitory actions of 17beta-oestradiol (10 microM) against spontaneous spike contractions and contractions to noradrenaline. 4. In summary, 17beta-oestradiol diminishes spontaneous spike contractions and the contractile response to noradrenaline in rat portal vein, by a non-genomic action.
1 It has been shown that magnetic fields (MFs) affect a variety of biological effects in animal brains. There have been few experiments on the effects of MFs on sleep. Therefore, we investigated whether extremely low frequency (ELF) MFs affect the sleep induced by clonidine, a central alpha(2) -adrenoceptor agonist. Clonidine produced dose-related increase of the sleeping time and dose-related decrease of the onset time in 2-day-old chicks.2 Exposure of chicks to MFs (5, 10, 20 G; for 3, 6, 9, 12 h) significantly increased the clonidine-induced sleep time as a direct function of intensity and duration of MF application. Clonidine reduced noradrenaline or tyrosine in the brain, an effect which was not further changed in animals exposed to MF.3 To determine whether the gamma amino butyric acid A (GABA(A) )/benzodiazepine (BZD) receptor system is involved in the decrease in clonidine-induced sleep caused by activation of central alpha(2) -adrenergic systems, we examined exposure of chicks to the effects of the BZD receptor antagonist flumazenil (0.5 mg kg(-1) , i.p.) and GABA(A) antagonist bicuculline (0.1 mg kg(-1) , i.p.) on clonidine-induced sleep. Bicuculline and flumazenil inhibited the increase of clonidine-induced sleep time by MFs. Clonidine or MFs did not change GABA levels in the brain.4 These results suggest that MFs can increase clonidine-induced sleep via a change of GABA(A) and BZD receptor system irrespective of the concentration of GABA or noradrenaline in the brain of 2-day-old chicks.
1. The present study investigates the effect of short-term experimental diabetes of 14-days duration on the beta-adrenoceptor subtypes of the rat heart. 2 .beta-adrenoceptor-mediated functional responses to submaximal doses of isoprenaline were enhanced in Langendorff-perfused hearts from diabetic rats, manifested as greater changes in tension, heart rate and rates of tension development (+dT/dt) and decline (-dT/dt). 3. Radioligand binding data demonstrated that total cardiac beta-adrenoceptor density and affinity for [3H]-dihydroalprenolol was unchanged by diabetes, although a decrease in beta1-adrenoceptor density and increase in beta2-adrenoceptor density was observed. 4. In conclusion, hearts from 14-day streptozotocin-induced diabetic rats demonstrate a number of alterations within the beta-adrenoceptor system. However, the enhanced beta-adrenoceptor-mediated responses to isoprenaline were not caused by an overall increase in density of beta-adrenoceptors, but were accompanied by changes in the ratio of the beta-adrenoceptor subtypes.
1. It is well established that presynaptic adenosine A1-receptor activation inhibits acetylcholine (ACh) release in the guinea-pig ileum. The present study extends this observation and examines a possible role for endogenous adenosine in modulating cholinergic nerve function. 2. The actions of the adenosine uptake blocker, dipyridamole, the adenosine deaminase inhibitor, erythro-9(2-hydroxy-3-nonyl)adenine (EHNA) and the A1-receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) were examined on electrically evoked neurogenic, cholinergic twitch contractions of the guinea-pig ileum. Some additional studies measuring [3H]-ACh release were also performed. 3. Adenosine and the selective A1-receptor agonist, 2-chloroadenosine (2-CA), inhibited electrically evoked contractions and, in the case of 2-CA, [3H]-ACh release. The actions were antagonized by DPCPX. At low concentrations, dipyridamole and EHNA enhanced the effect of adenosine causing a leftward shift of the concentration-response curve. In contrast, inhibition induced by 2-CA was unaffected by either dipyridamole or EHNA. 4. When applied alone at higher concentrations, EHNA and dipyridamole produced a concentration-dependent suppression of cholinergic neurotransmission. In both cases, the effect could be reversed by DPCPX. At the same concentration, DPCPX alone produced a small but consistent increase in twitch height and [3H]-ACh release. 5. The data confirm the existence of inhibitory presynaptic adenosine A1-receptors modulating cholinergic nerve function in the guinea-pig ileum and suggests that these receptors can be activated by endogenous adenosine released either as adenosine itself or as an ATP metabolite.
1. Alcohol-induced asthma is characterized by worsening of asthmatic symptoms after alcohol ingestion. Acetaldehyde, a metabolite of ethanol, is thought to be a main factor of alcohol-induced asthma. Although airway sensory nerves are known to be activated in asthma, there have been no studies investigating the role of tachykinins in the airway response to acetaldehyde. The purpose of the present study was to evaluate the involvement of tachykinins on acetaldehyde-induced bronchoconstriction in guinea-pigs. 2. After capsaicin desensitization or intravenous administration of 10 mg kg(-1) FK224, a NK1 and NK2 dual antagonist, airway responses to ascending doses (2.5-20 mg ml(-1)) of inhaled acetaldehyde was examined using a modified Konzett-Rössler method in guinea-pigs. 3. Inhalation of acetaldehyde induced bronchoconstriction in a dose-dependent manner. The FK224 failed to reduce the acetaldehyde-induced bronchoconstriction. Pretreatment with capsaicin did not alter the bronchoconstriction induced by acetaldehyde at a dose of 2.5-10 mg ml(-1). Pretreatment with capsaicin slightly, but significantly, inhibited bronchoconstriction induced by 20 mg ml(-1) of acetaldehyde. 4. The present results suggest that tachykinins are not involved in acetaldehyde-induced bronchoconstriction in guinea-pigs.
1. It has been postulated that stimulation of myocardial alpha-adrenoceptors is one of the primary mediators of the dysrhythmias which occur during periods of myocardial ischaemia and reperfusion. This study examines arrhythmogenesis during coronary artery occlusion and reperfusion in isolated perfused rat hearts from control animals and from rats with enhanced myocardial alpha-adrenoceptor responsiveness. 2. Rats were administered propylthiouracil (PTU) in their drinking water for 8 weeks. This treatment resulted in an enhanced responsiveness of isolated left atria to the alpha-adrenoceptor agonist phenylephrine compared with atria from control animals. 3. In Langendorff-perfused isolated hearts, the spontaneous rate of contraction was significantly lower in the PTU-pretreated group than in either age-matched or weight-matched controls. Occlusion of the left anterior descending artery (LAD) for 25 min resulted in ventricular tachycardia (VT) of similar incidence and duration in all groups and ventricular fibrillation (VF) in both control groups but not the PTU-pretreated group. 4. Following the 25-min ischaemic period the myocardium was reperfused for 10 min. The incidence and duration of VT and VF during this period was similar in all groups except that the duration of VF in the PTU-pretreated group was significantly lower than in controls. 5. In perfused hearts paced at 4 Hz, the incidence and duration of dysrhythmias during ischaemia and reperfusion was again similar in all groups, only the duration of VF being affected (reduced) by PTU-pretreatment. 6. In conclusion, this study does not lend support to the hypothesis that myocardial alpha-adrenoceptors have a primary role in arrhythmogenesis, but the data would support a role for these receptors in myocardial protection.
1. The neuropeptide substance P (SP) exerts an excitatory effect on sympathetic neurones by inhibiting a time- and voltage-dependent potassium current. During prolonged application of SP, the response desensitizes. The changes in kinetics of the SP response in single neurones after desensitization have been studied in an attempt to gain some insight as to the molecular mechanism of desensitization in live, functioning neurones. 2. Desensitization to SP resulted in subsequent SP responses being smaller, but the time course was unchanged in desensitized cells compared with non-desensitized cells. 3. Experimental manipulations were performed to decrease receptor and G protein function for comparison to desensitization. Intracellular application of GDPbetaS, to decrease G protein function, led to successive responses to agonist becoming smaller and slower. When functional muscarinic receptors were decreased by extracellular application of propylbenzilylcholine mustard (PrBCM), the response to muscarine became smaller, but the time course was unchanged compared with the change in time course produced by PrBCM vehicle alone. 4. The results have also been compared with simulations from a mathematical model of drug-receptor-G protein interactions. Under a constrained set of conditions, the model predicts that decreasing the size of the G protein pool will decrease both the magnitude and the time course of the response to agonist. Decreasing receptor levels results in a more efficient decrease in the magnitude of the response but no change in the time course of the response. 5. These data provide evidence that desensitization of the response to SP in single neurones results from a decrease in functional receptors.
1. The modulatory effects of agonists and antagonists of prejunctional alpha2-adrenoceptors on the electrical field stimulation (EFS, 0.3 ms, 12 V)-induced release of endogenous noradrenaline (NA) and the cotransmitter adenosine 5' triphosphate (ATP) were measured in endothelium-denuded segments of canine inferior mesenteric artery and compared with effects in mesenteric vein. The overflow of NA and ATP was evoked by long-duration (2 min) EFS at low frequency (4 Hz) and high frequency (16 Hz) of stimulation and was analysed using HPLC techniques with electrochemical detection and fluorescence detection, respectively. 2. The EFS-evoked overflow of both NA and ATP was significantly reduced by tetrodotoxin (1 microM) and guanethidine (10 microM) in the artery and vein. Desipramine (10 microM), a blocker of neuronal uptake of NA, increased the EFS (4 and 16 Hz)-evoked overflow of NA in both artery and vein. EFS-evoked overflow of NA in vein exceeded the NA overflow in artery at both 4 and 16 Hz in control preparations as well as in the presence of desipramine. However, the EFS-evoked overflow of ATP was equal in the artery and vein. 3. Stimulation of alpha2-adrenoceptors with clonidine (0.1 microM) and oxymethazoline (0.3 microM) reduced the EFS evoked overflow of NA in both artery and vein at 4 Hz, whereas the NA overflow at 16 Hz remained unchanged in both blood vessels. The overflow of ATP as well as of ADP (and hence ATP:ADP ratio) was unaffected by the alpha2-adrenoceptor agonists in the artery and vein. 4. In artery, blockade of alpha2-adrenoceptors with yohimbine at a concentration of 0.1 microM caused no effect on the NA overflow neither at 4 Hz nor at 16 Hz of EFS. Yohimbine at a concentration of 1 microM increased the overflow of NA at 4 Hz but not 16 Hz of EFS. In vein, however, yohimbine (0.1 and 1 microM) increased NA overflow at both 4 and 16 Hz of stimulation. Idazoxan (1 microM) increased the NA overflow in artery only at 4 Hz, whereas in vein idazoxan increased the NA overflow at both 4 and 16 Hz. No changes of EFS-evoked ATP overflow were observed in the presence of 0.1 microM yohimbine in both artery and vein. Greater concentration of yohimbine (i.e. 1 microM) increased the overflow of ATP in both the artery and vein only at 4 Hz EFS. Idazoxan (1 microM) enhanced the ATP overflow only at 16 Hz in vein. The overflow of ADP was affected by both yohimbine and idazoxan in a similar manner to the ATP overflow so that the ATP:ADP ratios were not changed. 5. In conclusion, sympathetic nerves in both mesenteric arteries and veins appear to release ATP along with NA. Release of NA in veins exceeds release of NA in arteries, whereas both the canine artery and vein release equal amount of ATP. At long-duration nerve stimulation (as might occur during stress) the alpha2-adrenoceptors appear to rather modulate release of NA than release of the cotransmitter ATP. The prejunctional autoinhibition of NA release is more effective at lower frequencies of nerve stimulation. The alpha2-adrenoceptor-mediated neuromodulation plays a greater role in veins than arteries. Quantitative differences in alpha2-adrenoceptor-mediated neuromodulation in the arteries and veins may participate to differing contributions of mesenteric blood vessels to the control of blood flow and volume distribution in splanchnic circulation.
1. The actions of a morpholinocatechol (UK42620) were studied in rat isolated atria preparations consisting of spontaneously beating left and right atrial pairs. 2. UK42620 produced positive inotropic and chronotropic responses and, in atria that were incubated with [(3)H]-noradrenaline, it also produced a massive increase in the release of radioactivity. 3. These actions of UK42620 were similar to those of tyramine and were blocked by the beta-adrenoceptor antagonist propranolol (0.3 microM) and by the neuronal uptake blocker desipramine (1 microM). 4. In the presence of desipramine, UK42620 but not tyramine produced a decrease in the stimulation-induced efflux of radioactivity that was antagonized by idazoxan. 5. Thus, UK42620 had prejunctional alpha(2)-adrenoceptor activity like that of clonidine- and tyramine-like activity releasing large amounts of noradrenaline.
1 The effects of stress in rats were evaluated by measuring changes in body weight and in responsiveness to noradrenaline (NA) in the isolated vas deferens and atria after the animals had been exposed to restraint or restraint and isolation.2 Animals which were subjected to restraint alone (1 h day(-1) for 3, 7 or 28 days) had a significantly reduced rate of body weight gain. This effect was not potentiated by the additional stress of isolation.3 Restraint alone did not produce significant changes in the responsiveness of the vas deferens to NA. However, adding isolation to restraint, as an additional stress, produced a further leftward shift of the NA dose-response curve for the vas deferens, so that there was a significant increase in sensitivity compared with control.4 There was a significant rightward shift in the NA dose-response curves or reduction in sensitivity in the atria from animals which had been restrained for 7 or 28 days. Isolation did not produce a further rightward shift in the NA dose-response curve.5 The results from this study indicate that the stress associated with repeated restraint reduces the rate of weight gain and reduces the responsiveness of the atria to NA. The responsiveness of the vas deferens to NA was increased by stress, but the combined effect of isolation and restraint was required to produce a significant effect. The differences in the effects of stress on these tissues could be associated with differences in presynaptic receptor populations.
1. The current study addressed how acute colitis, induced in male Sprague-Dawley rats by the administration of dextran sulphate sodium (DSS) in their drinking water, may affect some functional properties of the longitudinal muscle layer of the distal colon. 2. Dextran sulphate sodium was provided at a concentration of 3% for 3 or 7 days, or 5% for 7 days, and the rats were thereafter killed. Specimens of the distal colon were taken for histology or for organ bath experiments. 3. The colitis score increased significantly with increasing dose of DSS administered. At 5% concentration, there was sometimes even transmural inflammation. Functionally, there was a progressive increase in optimal preload (P(o)) for the contractile response to carbachol (1 microM), in relation to the severity of the colitis. At 5% DSS, the magnitude of the response to carbachol at P(o) was significantly increased compared with control rats. Such an effect could not be verified when, instead, K+ (60 mM) was used as a spasmogen. 4. It is concluded, that the colitis score increased in severity progressively with increasing amounts of DSS administered. The longitudinal muscle layer was functionally affected by the inflammation. Thus, there was a progressive increase in optimal preload for muscle contraction. Moreover, severe colitis resulted in an increase of the contractile response to carbachol, while a significant increase in the response to depolarization with K+ could not be found.
1. An oxazolo(3,2-a)pyridine derivative P5, described chemically as (+/-)-ethyl-7-(3-nitrophenyl)-5,8a-dimethyl-6-methoxycarbonyl-2,3,8,8a-tetrahydro-7H-oxazolo[3,2-a]pyridin-8-carboxylate, is a novel compound that has been synthesized as a possible antihypertensive prodrug of the 1,4-dihydropyridine type. Its antihypertensive activity was described in a previous study by the authors (Morán, Martin, Velasco, Martin, San Roman, Caballero, Puebla, Medarde & San Feliciano, 1997). 2. The aim of this work was to establish in vivo, the possible mechanisms participating in this antihypertensive action. Accordingly, we examined the effect of P5 on the pressor responses induced in pithed rats by noradrenaline (an alpha1-, alpha2- and beta-adrenoceptor agonist), xylazine (an alpha2-adrenoceptor agonist), methoxamine (an alpha1-adrenoceptor agonist), angiotensin I, angiotensin II, L-NAME (a nitric oxide synthase inhibitor) and BayK 8644 (a calcium channel agonist) and compared them with those of nifedipine, used as the reference drug. 3 Intravenous (i.v.) administration of P5 (2.5-10 mg kg(-1)) inhibited the pressor responses to noradrenaline (1 microg kg(-1)), xylazine (80 microg kg(-1)), angiotensin I (0.5 microg kg(-1)), angiotensin II (0.5 microg kg(-1)), BayK 8644 (30 microg kg(-1)) and L-NAME (10 mg kg(-1)). Nifedipine (10 microg kg(-1), i.v.) reduced the pressor responses to all these agonists and also to methoxamine (2 microg kg(-1)). 4. However, P5 was more effective than nifedipine in inhibiting these responses and its inhibitory effect lasted longer. Intravenous infusion of calcium gluconate (1 ml kg(-1) min(-1)) reversed the reduction in the pressor responses as a result of nifedipine. The effects of P5 were only reversed at 2-3 h after administration. 5 These results suggest that P5 has a strong capacity to inhibit the pressor responses to several agonists after its i.v. administration and that such effects are related to its potent antihypertensive activity.
1 Originally, the so-called 'adrenaline hypothesis' related the release of noradrenaline (NA) to stimulation of presynaptic beta2-receptors in nerve endings; now it confers a possible role to adrenaline taken up then released by nerves endings. It represents a potentially useful therapeutic pathway. The present study aims to investigate the effects of formoterol, a highly selective beta2-adrenoceptor agonist. 2 It was carried out in freely moving rats, the isotope dilution technique being used to measure the NA spill over rate (NA-SOR) and metabolic clearance rate (MCR). 3 A series of three results are reported. (a) When compared with adrenaline on equimolar basis, formoterol (2.3 micro kg-1 min-1) increased NA-SOR while mean arterial blood pressure was decreased and heart rate increased. Thus, it was difficult to separate a direct presynaptic effect from indirect baroreflex-dependent activation of the sympathetic system. (b) When formoterol was infused at 1 ng kg-1 min-1, a dose empirically defined to induce no haemodynamic effect, NA-SOR was significantly increased, while NA-MCR remained unchanged. (c) The NA-SOR response to formoterol was not amplified by the presynaptic alpha2-adrenoceptor blocker, yohimbine, in contrast to the NA-SOR response to adrenaline. 4 In conclusion, formoterol, a beta2-adrenoceptor agonist, is shown to increase the release and plasma concentration of NA while its clearance was not changed.
1. Permeabilization of cells mediated by P2X(7) receptors occurs to varied degrees in native and heterologous expression systems. Previous studies on P2X(7) receptors in parotid acinar cells suggested that ATP does not permeabilize these cells. 2. Modification of the assay conditions showed that ATP permeabilizes freshly dissociated rat parotid acinar cells to the fluorescent dye YOPRO-1. 3. The pharmacological and physiological properties of this effect indicate that permeabilization is mediated by the P2X(7) receptor. Adenosine 5'-triphosphate (ATP) and 3'-O-(4-benzoyl)benzoyl adenosine 5'-triphosphate (BzBzATP) were effective agonists with EC(50) values of 49.3 and 0.6 microM, respectively. 4. Permeabilization was best observed in low divalent cation concentrations and at physiological temperatures. Previous studies failed to detect permeabilization because of the sensitivity of this effect to temperature and divalent cations. 5. An important consideration in understanding the effect of divalent cations is that the fluorescence of YOPRO-1/nucleic acid complexes is directly quenched by addition of divalent cations. This must be considered if quantitative study of the interaction of divalent cations with P2X(7) receptors is carried out using fluorescent DNA-binding dyes. 6. In summary, our data show that P2X(7) receptors in parotid acinar cells can form large pores in the plasma membrane. This property likely contributes to signalling and may be cytotoxic and have particular significance in damaged or inflamed salivary glands.
1. Adenosine 5' triphosphate (ATP) (0.5-500 microM) or muscarine (0.1-1.0 microM) suppressed M-current/conductance (IM/gM) in B-cells of bullfrog sympathetic ganglion. Both agonists suppressed steady-state M-conductance (gM) at -30 mV and there was either no change or a slight increase in the time constants for gM activation (tau(a) at -30 mV) and deactivation (tau(d) at -50 mV). 2. It has previously been shown that experimental elevation of intracellular Ca2+ concentration ([Ca2+]i) suppresses gM and this is associated with decreases in both tau(a) and tau(d). As these changes in kinetics differ from those we observe with agonist application, our results cast doubt on the hypothesis that elevation of [Ca2+]i is involved in the transduction mechanism for ATP- or muscarine-induced gM suppression.
1 Despite the growing social interest in human urinary tract disorders, the aetiology of detrusor instability remains poorly understood. Myogenic and neural impairment of detrusor activity caused by CNS or autonomic injuries can results in dysfunctions of normal voiding of the bladder such as urinary incontinence.2 The contractility of human detrusor smooth muscle is critically dependent on acetylcholine-induced muscarinic receptor activation. Biochemical and functional in vivo and in vitro studies suggest the presence of an heterogeneous population of muscarinic receptor subtypes (M-1 -M-4 ) localized at muscular and neutral sites. There is increasing evidence on the prejunctional auto- and hetero-regulation of acetylcholine release from parasympathetic nerve endings in modulating detrusor muscle contraction during micturition.3 Activation of P2X purinoreceptors closely associated with the parasympathetic varicosities seems to be implicated to varying extent in the contractility in normal or instable human detrusor. Interestingly, P2X(1) subtype expression on smooth muscle increases considerably in the symptomatically obstructed bladder. A striking absence of P2X(3) and P2X(5) subtypes was observed in the cholinergic innervation of detrusor from patients with urgent incontinence. Thus, it is likely that alteration of the neural acetylcholine control can play a critical role in pathological states.4 If the failures in storage and voiding can be recognized urodynamically, considerable difficulties remain in investigating the underlying functional changes especially because the study of the pathophysiology requires techniques that can be justified in animals but not in humans.5 Recently, to solve this problem an alternative technique using human smooth muscle cells in culture has been developed. Human cell lines may be relevant in investigating the molecular pathways in physiological and pathological conditions.6 The potential development of novel molecular therapeutic strategies such as gene therapy and tissue engineering is also discussed.
1 The objective was to determine the role of muscarinic receptor subtypes in mediating contraction of the human detrusor smooth muscle in vitro. 2 Contractile responses of human detrusor muscle strips to carbachol were obtained in the absence and presence of a range of muscarinic antagonists (pirenzepine, methoctramine, 4-diphenylacetoxy-N-methyl piperidine methiodide (4-DAMP), tropicamide, oxybutynin and tolterodine). Affinity estimates (pKB values) were calculated for the antagonists and correlated with values at the cloned muscarinic receptor subtypes quoted in the literature. 3 Pirenzepine, methoctramine and tropicamide drugs that have high affinities at M1, M2 and M4-receptors, respectively, all had low affinities on the human detrusor (pKB values of 6.8, 6.9 and 6.5, respectively), whilst the M3-selective antagonist 4-DAMP had a high affinity (9.5). Schild plots for all four antagonists had slopes of unity indicating an action at a single receptor. Oxybutynin and tolterodine also acted as competitive antagonists with affinity estimates of 7.6 and 8.1, respectively. 4 When the antagonist affinities obtained on the bladder were plotted against the values published for these antagonists at the cloned muscarinic receptor subtypes, the best correlations were obtained for the m3- and m5-muscarinic receptor subtypes. 5 These data suggest that direct contractile responses of the human detrusor muscle to muscarinic receptor stimulation in vitro are mediated solely via the M3-muscarinic receptor subtype with no contribution from the major M2-receptor population.
1. In this study, the analysis of spontaneous baroreflex sensitivity (BRS) was applied to the dynamic assessment of cardiac anticholinergic drug effect in healthy male volunteers. 2. The anticholinergic effects of single intravenous (i.v.) injections of atropine (10 microg kg(-1)), glycopyrrolate (5 microg kg(-1)) and scopolamine (5 microg kg(-1)), as well as a 2-h infusion of glycopyrrolate (5 microg kg(-1) h(-1)) were investigated. Baroreflex sensitivity, a validated measure of cardiac parasympathetic reflex regulation, was repeatedly measured from 5-min recordings of electrocardiogram (ECG) and continuous blood pressure by using the sequence technique, a method based on detection of spontaneous fluctuations in blood pressure and heart rate. 3. Single injections of atropine, glycopyrrolate and scopolamine decreased the mean BRS by 71 +/- 32, 68 +/- 23 and 27 +/- 45%, respectively, whereas the slow glycopyrrolate infusion gradually decreased BRS (up to 83 +/- 11% reduction) and increased both systolic (SAP) and diastolic arterial pressures (DAP) (on an average, by 9 mmHg). 4. During the withdrawal of the parasympathetic blockade (indicated by increasing BRS), the proportion of baroreflex sequences in the recordings increased transiently from 10 up to 20-25%, probably reflecting the restoration of the baroreflex integrity and the baroreflex-induced attempt to counteract the blood pressure increase. 5. The sequence method to study BRS seems to be feasible in the assessment of cardiac anticholinergic drug effects, and it also provides good time resolution for the dynamic measurements.
1. The aim of our study was to ascertain the possible differences and/or similarities in natural tachykinin activity in vitro on lower urinary tract of large-sized animals as compared with data obtained in laboratory animals. 2. Besides tachykinins normally present in mammals, namely substance P (SP), neurokinin A (NKA) and neurokinin B (NKB), we tested non-mammalian tachykinins, such as eledoisin (ELED), physalaemin (PHYS), kassinin (KASS) and PG-kassinin II (PG-KASS II). 3. NKA, KASS and ELED were found to be the most potent peptides in contracting detrusor strips from porcine bladder. In particular, NKA showed a pD2 of 7.14, whereas KASS and ELED showed pD2 values of 7.20 and 7.22, respectively. The activity of NKB and PG-KASS II corresponded to 72.4 and 55.0% respectively of that of NKA. SP and PHYS activity corresponded to only 2% of that of NKA. 4. NKA (pD2 7.92) was the most active peptide in contracting bladder neck tissues as well. ELED and KASS were found to have lower, similar pD2 values (7.62 and 7.70, respectively), whereas NKB and PG-KASS II were much less active (pD2 7.12 and 6.74, respectively). Moreover, SP and PHYS showed an activity range lower than 2% of that of NKA. 5. The reported results confirm that, on pig vesical neck and detrusor, NK1 receptors represent a minority as compared with NK2 and NK3 receptors. By contrast, the presence of NK2 receptors is demonstrated by a greater potency of NKA. The presence of NK3 receptors both on detrusor and neck is evidenced by NKB activity and by results achieved with PG-KASS II.
