Sir,—In a recent report, Hirabayashi and colleagues [1] showed that subarachnoid administration of hyperbaric amethocaine (tetracaine) produced an unexpectedly higher level of analgesia in adolescents than in adults. The authors postulated that when adolescents lie in the supine horizontal position, the thoracic kyphotic curvature decreases because of the flexibility of their vertebral columns ...

Relatively low concentrations of methylxanthines increase spontaneous twitching in cultured muscle fibers; they also cause a second activity, escalation, which is the initiation and undiminished propagation of visible waves. The effect on twitching is abolished by depolarizing concentrations of K(+) or by tetrodotoxin; the effect on escalation is not. Escalation is prevented by removal of exter...

Procaine (1 X 10(-5)-1 X 10(-4) M), dibucaine (1 X 10(-5)-1 X 10(-4) M) and tetracaine (1 X 10(-6)-1 X 10(-5) M) caused an increase followed by a decrease in the rate of spontaneous afferent (A) discharges (D) accompanied with a decrease in the flow rate of perfusion solution from the pulmonary vein in the isolated lung of the bullfrog, but these local anesthetics only decreased the rate of A.D...

Etomidate, one of the most potent general anesthetics used clinically, acts at micromolar concentrations as an anesthetic and positive allosteric modulator of gamma-aminobutyric acid responses, whereas it inhibits muscle-type nicotinic acetylcholine receptors (nAChRs) at concentrations above 10 microm. We report here that TDBzl-etomidate, a photoreactive etomidate analog, acts as a positive all...

Positive allosteric modulators (PAMs) of a7 nicotinic acetylcholine receptors can enhance ion channel currents and downstream effects of a7 stimulation. We investigated the approach of using noncompetitive antagonists to regulate a7 receptor function, potentially distinguishing effects requiring ion channel currents from signaling induced by nonconducting states. Three small readily reversible ...

During the winter months, high doses of acetylcholine produced positive inotropic action without any chronotropic action on the perfused atropinised frog heart, in 5 out of 24 preparations. In the remaining preparations acetylcholine failed to produce any action and positive inotropic effect of acetylcholine on these preparations was noticed if they were perfused with the medium containing exce...

Positive allosteric modulators (PAMs) of a7 nicotinic acetylcholine receptors can enhance ion channel currents and downstream effects of a7 stimulation. We investigated the approach of using noncompetitive antagonists to regulate a7 receptor function, potentially distinguishing effects requiring ion channel currents from signaling induced by nonconducting states. Three small readily reversible ...

Intramembrane charge movements were studied in intact, voltage-clamped frog (Rana temporaria) skeletal muscle fibers in external solutions made increasingly hypertonic by addition of sucrose. The marked dependence of membrane capacitance on test potential persisted with increases in extracellular sucrose concentration between 350 and 500 mM. Charge movements continued to show distinguishable ea...