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D J Rowbotham

Publications and source records attributed to D J Rowbotham.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effect of halothane on K+ and carbachol stimulated [3H]noradrenaline release and increased [Ca2+]i in SH-SY5Y human neuroblastoma cells.

We have examined the effects of the volatile general anaesthetic agent, halothane, on K+ and carbachol stimulated [3H]noradrenaline release and associated increases in intracellular Ca2+ in a cultured human neuroblastoma cell line, SH-SY5Y. K+ (but not carbachol) stimulated [3H]noradrenaline release, and the increase in intracellular Ca2+ concentration was entirely extracellular Ca2+ dependent. Halothane produced a dose-dependent reduction in K+ evoked release of [3H]noradrenaline with significant inhibition (17%) occurring from 1.26 atm%. Basal and carbachol evoked release were unaffected. Halothane also produced a dose-dependent reduction in K+ evoked increases (measured at the peak) in intracellular Ca2+ with significant inhibition (29%) occurring from 0.88 atm%. K+ plateau, basal and carbachol evoked increases in intracellular Ca2+ were unaffected. These data suggest that halothane reduced Ca2+ entry through voltage-sensitive Ca2+ channels and implicate this important class of ion channel in the mechanism of anaesthesia.

Anesthetics, Inhalation↗
PubMed1996

mu- and kappa-opioids inhibit K+ evoked glutamate release from rat cerebrocortical slices.

We have examined the effects of a range of opioid receptor subtype selective agonists on K+ evoked glutamate release from perfused rat cerebrocortical slices. Dual application (S1 and S2) of K+ (46 mM) evoked dual monophasic glutamate release profiles. When areas under the release curves were calculated an S2/S1 ratio for control slices of 1.07 +/- 0.08 (n = 75) was obtained, this was reduced by 80% with EGTA (0.1 mM) treatment confirming the presence of a Ca2+ regulated release process, Morphine produced a dose-dependent inhibition of the S2/S1 ratio. At 1 microM this amounted to 78 +/- 12% (mean +/- SEM; n = 6). (D-Ala2,MePhe4,gly(ol)5)enkephalin (DAMGO; 60 +/- 12%, n = 6 at 1 microM), and spiradoline (53 +/- 14% at 1 and 71 +/- 11% at 100 microM, both n = 6) also inhibited glutamate release in a cyprodime (10 microM) and norbinaltorphimine (10 microM) reversible manner. (D-Pen2.5) enkephalin (DPDPE; 1 microM) was ineffective. All agents tested did not affect basal glutamate release. Collectively these data implicate a role for mu and kappa opioids in the control of evoked glutamate release and their potential for neuroprotective therapy.

Analgesics↗
PubMed1996

Effects of propofol and thiopentone on potassium- and carbachol-evoked [3H]noradrenaline release and increased [Ca2+]i from SH-SY5Y human neuroblastoma cells.

We have examined the effects of two intravenous anaesthetic induction agents, propofol and thiopentone, on K+ and carbachol evoked [3H]noradrenaline release from a human neuroblastoma cell line, SH-SY5Y. In this model, we have previously demonstrated that K+ evoked [3H]noradrenaline release was dependent on Ca2+ entry and carbachol evoked release was extracellular Ca(2+)- independent. Propofol inhibited K+ (100 mM)-evoked (IC50 of 42 +/- 11 microM), but not carbachol (1 mM)-evoked, [3H]noradrenaline release. Thiopentone inhibited both K+- and carbachol-evoked release with IC50 values of 116 +/- 15 microM and 169 +/- 39 microM, respectively. These inhibitory effects were not due to changes in the release dynamics, as assessed using perfused cells. Furthermore, thiopentone inhibition of carbachol-evoked release was not due to muscarinic receptor antagonism. Both propofol and thiopentone caused noncompetitive inhibition of K+-stimulated Ca2+ influx, with IC50 values of 127 +/- 7 microM and 121 +/- 10 microM, respectively. These effects were not due to interaction with GABAA receptors, but suggest that both compounds block voltage-sensitive Ca2+ channels. Thiopentone, but not propofol, inhibited carbachol-stimulated increased intracellular Ca2+ concentrations in the presence and absence of extracellular Ca2+. However, thiopentone had no effect on carbachol-stimulated inositol (1,4,5)-triphosphate formation, suggesting that thiopentone may directly inhibit Ca2+ release from intracellular stores.

Calcium↗
PubMed1996

Dose requirements, efficacy and side effects of morphine and pethidine delivered by patient-controlled analgesia after gynaecological surgery.

We have compared the dose requirements and side effects of morphine with those of pethidine when administered by patient-controlled analgesia in 40 patients (ASA I-II, 20-65 yr) after elective total abdominal hysterectomy. Patients were allocated randomly, in a double-blind manner, to receive either morphine (bolus dose 2 mg, lockout time 10 min) or pethidine (bolus dose 20 mg, lockout time 10 min) for postoperative pain relief. Mean 24-h morphine and pethidine consumption was 70 (SEM 6.2) mg and 660 (67.8) mg, respectively (ratio 1:9.4). There were no significant differences in postoperative sedation, nausea, pain relief and patient satisfaction (VAS 0-100 mm), and requirements for antiemetics. Four patients receiving pethidine were withdrawn because of postoperative confusion and one receiving morphine because of intractable nausea and vomiting. The 95% confidence interval for this difference between the groups for VAS scores of sedation, nausea and pain were approximately 30 mm.

Adult↗
PubMed1996

The effect of pre-incisional infiltration with lignocaine on postoperative pain after molar teeth extraction under general anaesthesia.

In a double-blind, placebo-controlled investigation, we studied the effects of pre-operative inferior alveolar nerve blockade and local anaesthetic intra-oral infiltration upon postoperative pain following third molar teeth extraction under general anaesthesia. Thirty six patients (12 male), mean (range) age 25.7 (18-40) years received an injection of 2% lignocaine 2 ml with 1:200,000 adrenaline around the inferior alveolar nerve and tissues adjacent to the third molar tooth on one side and of normal saline 2 ml in a similar fashion to the other side. We measured the pain on each side of the mandible on the 1st, 4th and 11th days after surgery using a visual analogue scale. The visual analogue pain score on the lignocaine and saline sides were 25/100 and 26/100 on day 1, 23/100 and 22/100 on day 4 and 0/100 and 1/100 on day 11. This study has a power of 80% to detect differences at the 5% level of significance of 11/100 on days 1 and 4 and 7/100 on day 11. We found no significant difference in the visual analogue scores between the lignocaine side and the saline side at any stage after the procedure.

Adolescent↗
PubMed1996

Nociceptin induced inhibition of K+ evoked glutamate release from rat cerebrocortical slices.

Nociceptin, an endogenous ligand for the orphan receptor ORL1, has recently been described. In this study we have shown that nociception inhibits 46 mM K(+)-stimulated glutamate release from rat perfused cerebrocortical slices with an IC50 of 51 nM. At 100 nM the inhibition amounted to 68 +/- 14% and was naloxone (10 microM)-insensitive excluding an activation of mu, delta and kappa opioid receptors. These data demonstrate the functional coupling of ORL1 in glutamatergic neurones and implicates a role for nociceptin in glutamatergic neurotransmission.

Amino Acid Sequence↗
PubMed1996

Cisapride. Drug interactions of clinical significance.

Cisapride is a prokinetic agent which restores motility of the gastrointestinal tract in conditions of decreased bowel transit. It may also alter the absorption of coadministered drugs. The absorption of morphine, diazepam, cyclosporin, alcohol (ethanol) and levodopa are increased. Initial absorption of cimetidine and raniditine is also increased, but overall absorption is lower due to increased bowel transit. The absorption of digoxin, propranolol and the anticoagulants warfarin and phenprocoumon appears unaffected by cisapride, although increase thrombotest values were seen with acenocoumarol (nicoumalone). Drug interactions leading to increased plasma concentrations of cisapride may produce an increase in adverse effects. The most important of these is QT interval prolongation and ventricular arrhythmias. Phenytoin does not appear to affect protein binding of cisapride. Cisapride metabolism is inhibited by the antifungals ketoconazole, fluconazole, itraconazole and miconazole, and by the antibacterials erythromycin, troleandomycin and clarithromycin. Cisapride should not be coadministered with these drugs. Cimetidine produces a small increase in cisapride plasma concentrations, which may be due to inhibition of metabolism. Cisapride absorption is unaffected by other antacids. Atropine may reverse the cisapride-induced increase in peristalsis. Prescribers should remain vigilant to the presence of these and other, as yet unreported, reactions.

Cisapride↗
PubMed1995

Glutamate uptake is not a major target site for anaesthetic agents.

We have examined the effects of thiopentone, propofol and ketamine 3-300 mumol litre-1, 3.6%, 2.4 rat MAC of isoflurane, 3.0%, 2.4 rat MAC of halothane and morphine 0.1-10 mumol litre-1 on uptake of [3H]glutamate into rat cerebrocortical and cerebellar synaptosomes. Corticol and cerebellar synaptosomes took up [3H]glutamate in a time-, concentration-, Na(+)-dependent and L-transpyrrolidine-2,4-dicarboxylate inhibitory manner. The Km and Vmax values for uptake were 8.6 mumol litre-1 and 1.7 nmol/min/mg protein and 2.2 mumol litre-1 and 0.7 nmol/min/mg protein in cortical and cerebellar preparations, respectively. At clinically relevant concentrations none of the agents tested influenced the uptake process. Our data suggest that the uptake of glutamate is not a major target site for anaesthetic or analgesic agents.

Anesthetics, Dissociative↗
PubMed1995

Do nitrous oxide and halothane influence opioid receptor binding in SH-SY5Y human neuroblastoma cells?

The site of interaction of opioids and inhalation anaesthetic agents is unknown, but may be at the level of the opioid receptor. In this study we have used SH-SY5Y human neuroblastoma cells, which express both mu and delta receptors, to examine the effects of halothane on the receptor binding profiles of [3H]diprenorphine (DPN), an opioid receptor antagonist, and [3H] [D-Ala2,MePhe4, Gly(ol)5]enkephalin (DAMGO), a mu receptor selective agonist. Binding of [3H]DPN and [3H]DAMGO was performed at 37 degrees C for 60 min in the presence of air, nitrous oxide (75%) or air containing halothane (0.5-5.0% v/v). Compared with air controls, neither 75% nitrous oxide nor 0.5, 1.0, 2.0 and 5.0% halothane influenced DPN binding variables. Binding of [3H]DAMGO was unaffected by 1.0% halothane, but 5.0% halothane reduced the affinity, with a modest increase in Kd (1.15 (0.16) to 1.7 (0.2) nmol litre-1) without effect on Bmax. Our data suggest that the site of opioid and volatile anaesthetic interaction is not at the opioid receptor.

Analgesics↗
PubMed1995

Inhibition by halothane of potassium-stimulated acetylcholine release from rat cortical slices.

1. Cholinergic neurones in the basal forebrain are linked to cortical activation and arousal. 2. The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) would significantly reduce depolarization-evoked acetylcholine (ACh) release from rat cortical slices. 3. ACh release was measured from rat cortical slices by a chemiluminescent technique. 4. Depolarization-evoked ACh release was inhibited significantly by halothane with an IC50 of 0.38%. This value equates to 0.3 MAC (the minimum alveolar concentration at which no movement occurs to a standard surgical stimulus in 50% of subjects) for the rat. 5. The potent effect of halothane on ACh release suggests that this mechanism may be a target for the action of volatile anaesthetic agents. This in vitro effect on ACh release is consistent with effects of halothane reported in vivo.

Acetylcholine↗
PubMed1994

Fentanyl inhibits the release of [3H]noradrenaline from SH-SY5Y human neuroblastoma cells.

We have examined the effect of fentanyl on [3H]noradrenaline release in a human neuroblastoma cell preparation, SH-SY5Y. Fentanyl produced a significant, concentration-dependent inhibition of [3H]noradrenaline release with IC50 values of 5.5 x 10(-6) mol litre-1 and 15.5 x 10(-6) mol litre-1 for carbachol- and potassium-evoked release, respectively. The small difference in IC50 between the two evoking stimuli may be explained by the weak binding affinity of fentanyl to muscarinic receptors (Ki = 570 nmol litre-1). The minimum concentrations at which a significant effect was observed were 0.3 x 0.10(-6) mol litre-1 and 10.0 x 10(-6) mol litre-1 for carbachol- and potassium-evoked release, respectively; these values are considerably in excess of the serum concentration of fentanyl required to produce analgesia. Naloxone failed to antagonize the fentanyl inhibition and, furthermore, morphine and an enkephalin had no effect on evoked release, implying a non-opioid receptor mediated effect.

Atropine↗
PubMed1994

Choline acetyltransferase activity of rat synaptosomes is sensitive to enflurane, but not halothane or isoflurane.

We have examined the activity of choline acetyltransferase (ChAT) in rat cortical synaptosomes in the presence of three volatile anaesthetic agents: enflurane, halothane and isoflurane. The Michaelis constant Km, for choline was reduced significantly (P = 0.012) in the presence of 6.5% enflurane (3 rat MAC) compared with control samples exposed to carrier air only, while maximum reaction velocity (Vmax) remained unaltered. The reduction in Km was also significant at enflurane concentrations of 4.4% (2 rat MAC) (P = 0.043) and 2.2% (1 rat MAC) (P = 0.043). Halothane 3% (2.5 rat MAC) and 4.5% isoflurane (3 rat MAC) had no effect on either kinetic property. If present in vivo, an enflurane-induced alteration in acetylcholine metabolism, through modified ChAT, may contribute to the convulsive properties of this anaesthetic.

Anesthetics↗
PubMed1994

Volatile anesthetic agents inhibit choline uptake into rat synaptosomes.

BACKGROUND: Acetylcholine is an excitatory neurotransmitter associated with the maintenance of consciousness. Choline uptake is the rate-limiting step in acetylcholine synthesis and may be a target for the action of volatile anesthetic agents. METHODS: [Methyl-3H]choline uptake was investigated using rat cortical synaptosomes. The preparation was exposed to air, as control, or equipotent partial pressures (2.4 rat MAC) of enflurane, halothane or isoflurane. In addition, the dose-response relation for halothane on [methyl-3H]choline uptake was studied. RESULTS: The maximum rate of uptake was reduced significantly by 24% in the presence of enflurane (5.5%, 2.4 rat MAC) and isoflurane (3.5%, 2.4 rat MAC) and by 38% in the presence of halothane (3%, 2.4 rat MAC) with no change in Michaelis constant in the presence of each agent. A linear relation between the inhibition of [methyl-3H]choline uptake and the concentration of halothane was observed up to 3% halothane above which there was no further inhibition. The concentration of halothane resulting in half-maximum inhibition of total choline uptake was 1.5%. CONCLUSIONS: Noncompetitive inhibition of [methyl-3H]choline uptake by volatile anesthetic agents has been demonstrated in the in vitro synaptosome preparation. If present in vivo reduction in anesthetic-sensitive choline uptake may reduce the presynaptic availability of acetylcholine and hence contribute to the process of anesthesia.

Anesthetics↗
PubMed1994

Studies on the mechanism of [3H]-noradrenaline release from SH-SY5Y cells: the role of Ca2+ and cyclic AMP.

1. The roles of both Ca2+ and adenosine 3':5'-cyclic monophosphate (cyclic AMP) in carbachol and K(+)-stimulated [3H]-noradrenaline release from SH-SY5Y human neuroblastoma cells were examined. 2. Both carbachol and K+ caused a time- and dose-related stimulation of [3H]-noradrenaline release. The release event in perfused cells was monophasic. Half-maximum stimulation measured in statically incubated (3 min) cells was 38 +/- 4 microM and 63 +/- 4 mM respectively. K+ (100 mM, added)-evoked release was greater than that produced by carbachol (1 mM). 3. Both carbachol and K+ caused a time- and dose (measured at 3 min)-related stimulation of cyclic AMP formation with half-maximum stimulation occurring at 5 +/- 1 microM and 49 +/- 2 mM respectively. In contrast to its effects on release, carbachol produced a greater stimulation of cyclic AMP formation than K+. 4. K(+)-stimulated [3H]-noradrenaline release was entirely dependent on Ca2+ entry as 2.5 mM Ni2+ abolished release. However, carbachol-evoked (1 mM) release appeared to be unaffected by Ni2+ pretreatment. 5. These data suggest that in SH-SY5Y cells, elevated cyclic AMP levels are not directly involved in [3H]-noradrenaline release. In addition, carbachol-stimulated release is largely independent of extracellular Ca2+ possibly implying a role for intracellular stored Ca2+ in the release process.

Calcium↗