Negative crosstalk between M1 and M2 muscarinic autoreceptors involves endogenous adenosine activating A1 receptors at the rat motor endplate

At the rat motor nerve terminals, activation of muscarinic M₁ receptors negatively modulates the activity of inhibitory muscarinic M₂ receptors. The present work was designed to investigate if the negative crosstalk between muscarinic M₁ and M₂ autoreceptors involved endogenous adenosine tonically activating A₁ receptors on phrenic motor nerve terminals. The experiments were performed on rat phrenic nerve-hemidiaphragm preparations loaded with [³H]-choline (2.5 μCi/ml). Selective activation of muscarinic M₁ and adenosine A₁ receptors with 4-(N-[3-clorophenyl]-carbamoyloxy)-2-butyryltrimethylammonium (McN-A-343, 3 μM) and R-N⁶-phenylisopropyladenosine (R-PIA, 100 nM), respectively, significantly attenuated inhibition of evoked [³H]-ACh release induced by muscarinic M₂ receptor activation with oxotremorine (10 μM). Attenuation of the inhibitory effect of oxotremorine (10 μM) by R-PIA (100 nM) was detected even in the presence of pirenzepine (1 nM) blocking M₁ autoreceptors, suggesting that suppression of M₂-inhibiton by A₁ receptor activation is independent on muscarinic M₁ receptor activity. Conversely, the negative crosstalk between M₁ and M₂ autoreceptors seems to involve endogenous adenosine tonically activating A₁ receptors. This was suggested, since attenuation of the inhibitory effect of oxotremorine (10 μM) by McN-A-343 (3 μM) was suppressed by the A₁ receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (2.5 nM), and by reducing extracellular adenosine with adenosine deaminase (0.5 U/mL) or with the adenosine transport blocker, S-(p-nitrobenzyl)-6-thioinosine (NBTI, 10 μM). The results suggest that the negative crosstalk between muscarinic M₁ and M₂ autoreceptors involves endogenous adenosine outflow via NBTI-sensitive (es) nucleoside transport system channelling to the activation of presynaptic inhibitory A₁ receptors at the rat motor endplate.     

Clinical and morphological features of a non-invasive papillary urothelial carcinoma, evolving from a urothelial inverted papilloma of the bladder

The work presents the clinical and morphological aspects in a case of a non-invasive papillary urothelial carcinoma low grade developed on a bladder inverted papilloma from a patient aged 38 years. the tumour is distinguished by setting up at young age, female sex, by location on the side wall of the bladder and by rare association with inverted urothelial papilloma.     

Efficacy and Safety of a New Streptokinase Regimen with Enoxaparin in Acute Myocardial Infarction

OBJECTIVE: To compare a new streptokinase regimen combined with either enoxaparin or unfractionated heparin (UFH) and the traditional streptokinase regimen combined with UFH in patients with acute myocardial infarction (AMI). METHODS: 412 patients (<75 years), hospitalized within 6 hours of the onset of chest pain, were allocated thrombolytic therapy by the treating physician: streptokinase 0.75 MU/10 minutes, repeated if no coronary reperfusion after one dose, plus enoxaparin 40 mg intravenously followed by 1 mg/kg bodyweight subcutaneously at 12-hour intervals for 5-7 days (n = 102); the same streptokinase regimen plus UFH 1000 IU/60 minutes intravenously for 48-72 hours ( n = 106); or streptokinase 1.5 MU/60 minutes plus the same UFH regimen (n = 204). All patients received 250-325 mg aspirin/day. Coronary reperfusion rates, 30-day mortality and hemorrhagic complications were recorded. RESULTS: Coronary reperfusion rates with 0.75 streptokinase + enoxaparin (78.4%) and 0.75 streptokinase + UFH (74.5%) were significantly higher than those with 1.5 streptokinase + UFH (62.2%), but there was no significant difference between the groups receiving the new regimen. Overall 30-day mortality (6.3%) was significantly lower than with 1.5 streptokinase + UFH (12.7%) ( p = 0.037). The incidence of major and minor hemorrhagic events was similar in all groups. CONCLUSIONS: The accelerated streptokinase regimen was well tolerated and resulted in a significantly higher coronary reperfusion rate and significantly lower mortality compared with the traditional regimen. The 0.75 streptokinase + enoxaparin combination was at least as efficacious as the 0.75 streptokinase + UFH combination and is preferred because of its ease of administration and predictable anticoagulant effect.     

Activation of P2Y6 receptors increases the voiding frequency in anaesthetized rats by releasing ATP from the bladder urothelium

BACKGROUND AND PURPOSE

Despite the abundant expression of the UDP-sensitive P2Y₆ receptor in urothelial cells and sub-urothelial myofibroblasts its role in the control of bladder function is not well understood.

EXPERIMENTAL APPROACH

We compared the effects of UDP and of the selective P2Y₆ receptor agonist, PSB0474, on bladder urodynamics in anaesthetized rats; the voided fluid was tested for ATP bioluminescence. The isolated urinary bladder was used for in vitro myographic recordings and [³H]-ACh overflow experiments.

KEY RESULTS

Instillation of UDP or PSB0474 into the bladder increased the voiding frequency (VF) without affecting the amplitude (A) and the duration (Δt) of bladder contractions; an effect blocked by the P2Y₆ receptor antagonist, MRS2578. Effects mediated by urothelial P2Y₆ receptors required extrinsic neuronal circuitry as they were not detected in the isolated bladder. UDP-induced bladder hyperactvity was also prevented by blocking P2X3 and P2Y₁ receptors, respectively, with A317491 and MRS2179 applied i.v.. UDP decreased [³H]-ACh release from stimulated bladder strips with urothelium, but not in its absence. Inhibitory effects of UDP were converted into facilitation by the P2Y₁ receptor antagonist, MRS2179. The P2Y₆ receptor agonist increased threefold ATP levels in the voided fluid.

CONCLUSIONS AND IMPLICATIONS

Activation of P2Y₆ receptors increased the voiding frequency indirectly by releasing ATP from the urothelium and activation of P2X3 receptors on sub-urothelial nerve afferents. Bladder hyperactivity may be partly reversed following ATP hydrolysis to ADP by E-NTPDases, thereby decreasing ACh release from cholinergic nerves expressing P2Y₁ receptors.     

Determinants of HIV Infection Among Female Sex Workers in Two Cities in the Republic of Moldova: The Role of Injection Drug Use and Sexual Risk

In 2009–2010, females who reported having vaginal, anal or oral sex in exchange for money in the previous year, ≥16 years, and living in either Chisinau (n = 299) or Balti (n = 359), Moldova, were recruited into a respondent driven sampling survey. One fifth reported ever injecting drugs and over 30 % ever had sexual intercourse with men who inject drugs. In both cities, condom use with permanent and casual partners was much lower than condom use with commercial partners. In Chisinau, 6.9 % and in Balti, 24.7 % tested positive for HIV; 18 and 23.7 % had antibodies to hepatitis C; 9.1 and 8.9 % had antibodies to HBV; and, 8.4 and 6.1 % tested positive for syphilis. HIV seropositive FSW in either city were more likely to have ever injected drugs and to be infected with HCV. Limited government initiative and drastic reductions in international funding will likely impact urgently needed HIV prevention and harm reduction services targeting FSW in Moldova.     

Modulation by adenosine of both muscarinic M1-facilitation and M2-inhibition of [3H]-acetylcholine release from the rat motor nerve terminals

The crosstalk between adenosine and muscarinic autoreceptors regulating evoked [3H]-acetylcholine ([3H]-ACh) release was investigated on rat phrenic nerve-hemidiaphragm preparations. Motor nerve terminals possess facilitatory M1 and inhibitory M2 autoreceptors that can be activated by McN-A-343 (1-30 microm) and oxotremorine (0.3-100 microm), respectively. The muscarinic receptor antagonist, dicyclomine (3 nm-10 microm), caused a biphasic (inhibitory/facilitatory) effect, indicating that M1-facilitation prevails during 5 Hz stimulation trains. Concomitant activation of AF-DX 116-sensitive M2 receptors was partially attenuated, as pretreatment with M1 antagonists, muscarinic toxin 7 (MT-7, 0.1 nm) and pirenzepine (1 nm), significantly enhanced inhibition by oxotremorine. Activation of A2A-adenosine receptors with CGS 21680C (2 nm) (i) potentiated oxotremorine inhibition, and (ii) shifted McN-A-343-induced facilitation into a small inhibitory effect. Conversely, the A1-receptor agonist, R-N6-phenylisopropyl adenosine (R-PIA, 100 nm), attenuated the inhibitory effect of oxotremorine, without changing facilitation by McN-A-343. Synergism between A2A and M2 receptors is regulated by a reciprocal interaction with facilitatory M1 receptors, which may be prevented by pirenzepine (1 nm). During 50 Hz-bursts, facilitation (M1) of [3H]-ACh release by McN-A-343 disappeared, while the inhibitory (M2) effect of oxotremorine became predominant. This muscarinic shift results from the interplay with A2A receptors, as it was precluded by the selective A2A receptor antagonist, ZM 241385 (10 nm). In conclusion, when the muscarinic M1 positive feedback loop is fully operative, negative regulation of ACh release is mediated by adenosine A1 receptors. During high frequency bursts, tonic activation of A2A receptors promotes M2 autoinhibition by braking the M1 receptor operated counteraction.