Comparison of the effects of intravenous alfentanil and esmolol on the cardiovascular response to double-lumen endobronchial intubation.

We compared the effect of alfentanil 10 microg.kg-1 and esmolol 1.5 mg.kg-1 on the cardiovascular responses to laryngoscopy and double-lumen endobronchial intubation in two groups of 20 ASA 2-3 patients undergoing pulmonary surgery, in a randomised double-blind study. Arterial pressure and heart rate decreased after induction of anaesthesia and increased after intubation in both groups (p < 0.05) but remained at or below baseline values, and changes were comparable in both groups. Plasma catecholamine concentrations decreased after induction of anaesthesia in both groups (p < 0.05). Epinephrine concentrations increased in the esmolol group after intubation (p < 0.05) but remained below baseline in the alfentanil group (p < 0.05). Norepinephrine concentrations increased significantly in both groups after intubation but were higher in the esmolol group (p < 0.05). Although both esmolol 1.5 mg.kg-1 and alfentanil 10 microg.kg-1 similarly attenuated the arterial pressure and heart rate response to endobronchial intubation, plasma catecholamine concentrations increased in the esmolol group to values greater than previously reported after tracheal intubation.

Effects of nociceptin and endomorphin 1 on the electrically stimulated human vas deferens.

AIMS: To examine the effects of nociceptin (NC) and endomorphin 1 (EM1) on electrical field stimulation (EFS)-induced contractions of the human vas deferens (hVD). METHODS: Concentration-response curves to NC and EM1 were constructed in the absence and in presence of peptidase inhibitors (PI). In some experiments a NC receptor antagonist, [Phe1psi(CH2-NH)Gly2]NC(1-13)NH2 [F/G], 10 microM) or naloxone (1 microM) were included. RESULTS: All data are mean(95%CI). In the presence of PI, NC inhibited twitches (Emax = 67(44,90)%; pEC50 = 7.28(6.95,7.61)). NC inhibition was sensitive to [F/G]. EM1 also inhibited twitches both in the absence (Emax = 82(73,91)% pEC50 = 7.07(6.92,7.22)) and presence (Emax = 83(76,90)%; pEC50 = 7.00(6.91, 7.09)) of PI. EM1 inhibition was sensitive to naloxone. CONCLUSIONS: These data suggest that hVD express NC and opioid receptors that inhibit neurogenic contractions.

Lidocaine added to a tracheostomy tube cuff reduces tube discomfort.

PURPOSE: To examine whether lidocaine diffusion across an endotracheal tube cuff affects tracheostomy tube discomfort. METHODS: Two tracheostomy tube cuffs were inflated with 5 ml lidocaine 4% solution and air at 20 cmH2O, and then placed in 20 ml distilled water at 37 degrees C. After vigorous stirring, 100 microl of this water was then sampled immediately then 1, 2, 4, 8, 24 hr later to measure lidocaine concentration by high-performance liquid chromatography. Sixteen patients undergoing tracheostomy following oral cancer resection were randomly assigned to two groups: lidocaine (n=8) and placebo (n=8). A tracheostomy tube cuff was inflated with 5 ml lidocaine 4% or saline 0.9% and air to a cuff pressure of 20 cmH2O, in the lidocaine and placebo groups respectively. Tube discomfort was evaluated using a visual analogue scale at 0, 0.5, 1, 2 and 4 hr after lidocaine or saline administration. Neither analgesics nor sedatives was given during the evaluation period. RESULTS: Lidocaine time-dependently diffused across the tracheostomy tube cuff. Thirty and 60 min after cuff inflation lidocaine concentrations in the water bath reached approximately 8 and 17 microg x ml(-1) representing 160 and 340 microg in 20 ml of water, respectively. The VAS decreased from 53.5 +/- 10.6 to 25.1 +/- 9.8 mm (P < 0.01) 0.5 hr following lidocaine administration which continued until the end of evaluation period. In the placebo group, VAS did not change. CONCLUSION: Lidocaine diffusion across the tracheostomy tube cuff reduces tube discomfort.

Cardiovascular and catecholamine responses during endovascular and conventional abdominal aortic aneurysm repair.

OBJECTIVES: To compare changes in plasma catecholamines, acid-base status and cardiovascular dynamics in patients undergoing endovascular or conventional infrarenal abdominal aortic aneurysm (AAA) repair under standard general anaesthesia. DESIGN: Prospective cohort study. MATERIALS: 30 patients scheduled for elective infrarenal AAA repair. METHODS: Plasma epinephrine and norepinephrine concentrations, acid-base status and cardiovascular measurement were compared before surgery, and 5 min after aortic clamping and clamp release (conventional group) or occlusion and release (endovascular group) in patients undergoing endovascular (n = 15) or conventional AAA repair (n = 15). RESULTS: Arterial pH (p < 0.005) and base deficit (p < 0.05) increased, and plasma bicarbonate decreased (p < 0.005) during aortic cross-clamping in the conventional group. pH decreased further (p < 0.005), and base deficit and pCO2 increased (both p < 0.005) after clamp release. These changes were significantly greater than during endovascular repair, in whom within-group changes were not statistically significant. Values were similar in the two groups 30 min after reperfusion. Plasma epinephrine concentrations increased during conventional surgery (p < 0.05) and were greater than in the endovascular group (p < 0.05). Plasma norepinephrine concentrations increased during surgery in both groups but the changes were not statistically significant. CONCLUSIONS: Plasma catecholamine concentrations, changes in cardiovascular variables and acid-base status were increased during conventional compared with endovascular AAA repair.

Quantal calcium release in electropermeabilized SH-SY5Y neuroblastoma cells perfused with myo-inositol 1,4,5-trisphosphate.

Continuous perfusion of immobilized electropermeabilized SH-SY5Y neuroblastoma cells was utilised as a novel approach to the assessment of incremental activation and inactivation of myo-inositol 1,4,5-trisphosphate (IP3)-induced calcium (Ca2+) mobilisation (IICM). SH-SY5Y cells when stimulated with sub-optimal IP3 exhibited a rapid concentration dependent activation of Ca2+ mobilization followed by a partial inactivation. Although this partial inactivation allowed net Ca2+ mobilized to be stringently returned to basal levels, a concentration-dependent depletion of the store was maintained while ever perfusion with the stimulating IP3 concentration was sustained. This partial inactivation of IP3-induced quantal Ca2+ release (QCR) was only compromised if cells, with replete Ca2+ stores, were perfused with supra-maximally effective concentrations of IP3 (5-10 microM). Thus, at supra-optimal IP3 concentrations, a reproducible plateau of Ca2+ release lying 50-150 nM above the basal Ca2+ concentration was observed. Feedback on IP3R sensitivity by gross cytosolic Ca2+ levels could be eliminated as the sustained and exclusive mediator of incremental activation/inactivation cycle of IICM in SH-SY5Y cells, since released Ca2+ was perfused away from the immobilized cells. Thus, while ever the cells were continuously perfused with IP3, impressive incremental inactivation was apparent. Additionally, IP3R partial agonists were found to exhibit lower intrinsic activity for both activation and inactivation of QCR, suggesting that ligand-induced inactivation of the IP3R was more important than inactivation mechanisms reliant on either Ca2+ flux through the channel and/or calcium store depletion. Therefore, we suggest that, in perfused SH-SY5Y cells, the most parsimonious explanation of our data is that IP3 binding probably activates and then partially inactivates its receptor in a concentration-dependent fashion to produce the QCR phenomenon.

Recovery of respiratory ciliary function after depression by inhalation anaesthetic agents: an in vitro study using nasal turbinate explants.

We have developed a human tissue preparation suitable for measurement of cilia beat frequency derived from nasal turbinates. Cilia beat frequency of turbinate explants from 11 patients did not change significantly over a 10-day observation period while maintained in an incubator, with mean cilia beat frequency of 13.1 (SEM 0.3) Hz to 14.4 (0.2) Hz (ANOVA for repeated measures, P = 0.168). We have used this preparation to investigate recovery of ciliary function after depression by inhalation anaesthetic agents. Eight or nine turbinate explants were exposed to three times the minimum alveolar concentration (MAC) of halothane, enflurane or isoflurane for a period of 1 h and thereafter to a period of air washout. After exposure to the inhalation agent there was a significant reduction in cilia beat frequency with all three agents: halothane 14.3 (0.4) Hz to 9.5 (0.3) Hz; enflurane 13.7 (0.6) Hz to 10.5 (0.5) Hz;isoflurane 15.9 (0.6) Hz to 10.6 (0.3) Hz. Cilia beat frequency returned to values after air washout that were not significantly different from baseline after 90 min of washout of halothane and 60 min of washout of enflurane and isoflurane (repeated measures ANOVA, unpaired t test; P = 0.01 at 60 min and P = 0.31 at 90 min washout for halothane; P = 0.83 at 60 min washout for enflurane; P = 0.26 at 60 min washout for isoflurane).

Synthetic phosphorothioate-containing analogues of inositol 1,4,5-trisphosphate mobilize intracellular Ca2+ stores and interact differentially with inositol 1,4,5-trisphosphate 5-phosphatase and 3-kinase.

Intracellular Ca2+ stores in permeabilized SH-SY5Y neuroblastoma cells were mobilized by D-myo-inositol 1,4,5-trisphosphate [D-Ins(1,4,5)P3] and two of its synthetic analogues, DL-myo-inositol 1,4-bisphosphate 5-phosphorothioate (DL-InsP3-5S) and DL-myo-inositol 1,4,5-trisphosphorothioate (DL-InsP3S3). The concentrations of D-Ins(1,4,5)P3, DL-InsP3-5S, and DL-InsP3S3 required for half-maximal release were 0.11, 0.8, and 2.5 microM, respectively. All agents were full agonists, releasing 55-60% of sequestered 45Ca2+. D-Ins(1,4,5)P3-induced mobilization of Ca2+ was transient, and Ca2+ reuptake followed D-Ins(1,4,5)P3 metabolism closely. DL-InsP3S3-induced mobilization was persistent, consistent with the resistance of this analogue to metabolic enzymes. In contrast, DL-InsP3-5S-induced Ca2+ mobilization was followed by reuptake of Ca2+, albeit at a slower rate than that seen with D-Ins(1,4,5)P3. DL-InsP3-5S and DL-InsP3S3 were resistant to D-Ins(1,4,5)P3 5-phosphatase and potently inhibited the enzyme, with Ki values of 6.8 and 1.7 microM, respectively. DL-InsP3S3 was resistant to D-Ins(1,4,5)P3 3-kinase and was a very weak inhibitor of the enzyme (Ki = 230 microM). The ability of DL-InsP3-5S to inhibit D-Ins(1,4,5)P3 phosphorylation (apparent Ki = 5 microM) and its loss of Ca(2+)-releasing ability on incubation with D-Ins(1,4,5)P3 3-kinase suggest that this analogue may undergo phosphorylation to inositol 1,3,4-trisphosphate 5-phosphorothioate. These differential and complementary properties of DL-InsP3-5S and DL-InsP3S3 may be useful in dissecting the roles of D-Ins(1,4,5)P3 and D-myo-inositol 1,3,4,5-tetrakisphosphate in Ca2+ homeostasis.

Interaction of synthetic D-6-deoxy-myo-inositol 1,4,5-trisphosphate with the Ca2(+)-releasing D-myo-inositol 1,4,5-trisphosphate receptor, and the metabolic enzymes 5-phosphatase and 3-kinase.

The ability of D-6-deoxy-myo-inositol 1,4,5-trisphosphate [6-deoxy-Ins(1,4,5)P3], a synthetic analogue of the second messenger D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], to mobilise intracellular Ca2+ stores in permeabilised SH-SY5Y neuroblastoma cells was investigated. 6-Deoxy-Ins(1,4,5)P3 was a full agonist (EC50 = 6.4 microM), but was some 70-fold less potent than Ins (1,4,5)P3 (EC50 = 0.09 microM), indicating that the 6-hydroxyl group of Ins(1,4,5)P3 is important for receptor binding and stimulation of Ca2+ release, but is not an essential structural feature. 6-Deoxy-Ins(1,4,5)P3 was not a substrate for Ins (1,4,5)P3 5-phosphatase, but inhibited both the hydrolysis of 5-[32P]+ Ins (1,4,5)P3 (Ki 76 microM) and the phosphorylation of [3H]Ins(1,4,5)P3 (apparent Ki 5.7 microM). 6-Deoxy-Ins (1,4,5)P3 mobilized Ca2+ with different kinetics to Ins(1,4,5)P3, indicating that it is probably a substrate for Ins (1,4,5)P3 3-kinase.

Coupling of muscarinic receptors to the mobilization of intracellular Ca2+ stores in permeabilized SH-SY5Y human neuroblastoma cells.

Intracellular stores of Ca2+ were mobilized transiently by carbachol in suspensions of electrically permeabilized SH-SY5Y cells. The kinetics and the dose-dependence of this mobilization paralleled carbachol-induced increases in inositol 1,4,5-trisphosphate (InsP3) mass [for both parameters EC50 (concn. giving half-maximal response) = 60-70 microM]. Guanosine 5'-[gamma-thio]triphosphate enhanced the maximal effect and the potency of carbachol on Ca2+ mobilization and InsP3 mass, but caused separation of the dose-response curves (EC50 = 0.6 microM and 5.6 microM respectively). These data show that functional coupling of muscarinic receptors to Ca2+ mobilization can be maintained after permeabilization, reveal major effects of guanine nucleotides on agonist-induced Ca2+ mobilization and provide a basis for explanation of discrepancies between agonist potency on InsP3 concentration and Ca2+ mobilization in intact cells.

Inositol 1:2-cyclic,4,5-trisphosphate is only a weak agonist at inositol 1,4,5-trisphosphate receptors.

The activity of inositol 2,4,5-trisphosphate and inositol 1:2-cyclic,4,5-trisphosphate relative to inositol 1,4,5-trisphosphate was examined by two assays; firstly, in a binding assay using rat cerebellar membranes, and secondly, in a Ca2+-mobilization assay using permeabilized Swiss 3T3 cells. In both assays the first two phosphates have a potency at least an order of magnitude less than inositol 1,4,5-trisphosphate. The possible reasons for differences between these results and previous data are discussed, as are the implications for any putative physiological role for the cyclic trisphosphate.

Stereospecific mobilization of intracellular Ca2+ by inositol 1,4,5-triphosphate. Comparison with inositol 1,4,5-trisphosphorothioate and inositol 1,3,4-trisphosphate.

The stereo specificity of myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to mobilize Ca2+ from an intracellular store has been examined in permeabilized rat pituitary-tumour GH3 and Swiss 3T3 cells. A comparison of D-Ins(1,4,5)P3 with the synthetic enantiomer L-Ins(1,4,5)P3 and the racemate DL-Ins(1,4,5)P3 clearly demonstrates the marked stereospecificity of the response. Whereas D-Ins(1,4,5)P3 released 30-50% of non-mitochondrially-bound Ca2+ with a EC50 (concentration producing 50% of maximal response) of 200 nM, the L isomer was both substantially less potent and efficacious. A high concentration of the L isomer (10 microM) did not significantly shift the dose-response curve for the D isomer in Swiss 3T3 cells, suggesting that the less active isomer is probably a very weak agonist. Other studies revealed, in contrast with previous work, that the other naturally occurring isomer, D-Ins(1,3,4)P3, was essentially inactive in releasing Ca+, whereas a novel 5-phosphatase-resistant analogue, DL-myo-inositol 1,4,5-trisphosphorothioate, was a relatively potent full agonist in GH3 cells. These data reveal, for the first time, the stereoselectivity of the intracellular receptor associated with Ca2+ release. They also provide evidence for the activity of the novel phosphorothioate analogue of Ins(1,4,5)P3, but suggest that D-Ins(1,3,4)P3 is not involved in cellular Ca2+ mobilization.

Endogenous dopamine release from rat striatal slices and its regulation by D-2 autoreceptors: effects of uptake inhibitors and synthesis inhibition.

The effects of various dopaminergic drugs on the spontaneous and veratrine-stimulated release of endogenous dopamine (DA) from superfused rat striatal slices have been examined using a high-sensitivity HPLC system. The DA uptake inhibitor nomifensine greatly increased both veratrine-stimulated and spontaneous DA release, whilst the effects of the more potent and selective inhibitor GBR 12921 were much smaller. The DA agonists pergolide and LY 171555 reduced both spontaneous and veratrine-stimulated DA release; conversely, the D-2 selective antagonist l-sulpiride stereospecifically increased spontaneous and veratrine-stimulated release, and blocked the effects of pergolide and LY 171555. Inhibition of DA synthesis did not directly influence the actions of either pergolide or sulpiride. These studies indicate that nomifensine may have a DA-releasing action in addition to its uptake blocking action, the regulation of endogenous DA release by D-2 autoreceptors shows properties similar to those reported previously for radiolabelled DA release, with the novel finding that spontaneous release is also regulated, the autoreceptors do not appear to selectively influence newly synthesised DA release.

Release of endogenous dopamine and cholecystokinin from rat striatal slices: effects of amphetamine and dopamine antagonists.

The release of immunoreactive cholecystokinin (CCK) and dopamine was monitored simultaneously from superfused rat striatal slices. Exposure of the tissue to medium containing elevated K+ or veratrine, induced a marked release of both substances. The addition of dopamine (10(-7) and 10(-6) M), the dopamine agonist pergolide (10(-7) M), the D2-antagonist sulpiride (1 microM) or the D1-antagonist (SCH 23390) had no significant effect on basal overflow or on evoked release of CCK. On the other hand, preincubation of striatal slices with D-amphetamine (10(-5) M) enhanced basal and veratrine-stimulated dopamine release but markedly suppressed evoked CCK release. Sulpiride blocked this action of amphetamine whereas SCH 23390 was ineffective. The data suggests that whereas it is difficult to observe any effects of exogenous dopamine agonists or antagonists on evoked CCK release, endogenously released dopamine appears to interact with D2-receptors to suppress evoked CCK release from rat striatal slices.

Differences between the release of radiolabelled and endogenous dopamine from superfused rat brain slices: effects of depolarizing stimuli, amphetamine and synthesis inhibition.

Direct comparisons between radiolabelled and endogenous dopamine (DA) release from superfused rat brain slices have been made. Striatal slices were prelabelled with [3H]dopamine ([3H]DA), then superfused at 0.5 ml/min and the released catecholamines analyzed by HPLC with electrochemical detection and the radioactivity present in superfusate fractions also counted. Two successive 50 mM K+ pulses released similar amounts of endogenous DA from striatal slices, but the second pulse released 50% less [3H]DA than the first. A K+ gradient (5-53 mM) released relatively more [3H]DA compared to endogenous DA at lower K+ than at higher K+ concentrations. Blockade of DA synthesis in vitro by 50 microM a-methyl-p-tyrosine greatly reduced K+-induced endogenous DA release without any major effect on [3H]DA release. Amphetamine (10 microM) greatly increased both basal DA release and release induced by a 5 microM veratrine pulse, but its effects were 3-4 times greater on endogenous than on [3H]DA release. Although a-methyl-p-tyrosine reduced both basal and veratrine-stimulated endogenous DA release from non-prelabelled tissue by over 50% in either the presence or absence of amphetamine, it did not decrease endogenous DA release from prelabelled tissue. These studies indicate that labelled and endogenous amine release do not always occur in parallel, and that major causes of discrepancy between them may include the presence of a large newly-synthesized component in endogenous release and the uneven distribution of labelled amine within endogenous releasable pools. The results also suggest that the prelabelling process itself may alter the pools contributing to subsequent endogenous release. In the light of these studies, the assumption that labelled amine release provides an accurate marker for endogenous release should be reconsidered.