An inhibitory effect of ethanol on adrenergic neuromuscular transmission in the guinea-pig vas deferens

Effects of ethanol on adrenergic neuromuscular transmission were investigated in the isolated vas deferens of the guinea-pig. The contractile responses to adrenergic nerve stimulation were depressed by ethanol in a concentration-dependent, reversible manner at a concentration range between 25 and 500 mM. Ethanol also depressed the contractions induced by exogenous noradrenaline. The resting membrane potentials recorded intracellularly from the smooth muscle cells were not affected by the alcohol. The excitatory junction potentials (EJPs) evoked by nerve stimulation decreased in amplitude, but the facilitation phenomena observed with repetitive stimulation remained unaltered. Ethanol slightly increased the frequency of the spontaneous EJPs, but decreased their amplitude. The extracellularly recorded action potentials from the small sympathetic nerve bundles innervating the vas deferens were suppressed by high concentrations of ethanol (more than 200 mM). These results indicate that ethanol inhibits adrenergic neuromuscular transmission in the vas deferens probably through depressing the sensitivity of the postsynaptic membrane to the transmitter and a block of axonal conduction in the presynaptic nerve terminals.

In vivo effect of methylmercury on protein synthesis in peripheral nervous tissues of the rat

The in vivo rates of protein synthesis in the peripheral nervous tissues of methylmercury-treated rats (10 mg/kg/day, for 7 days) have been estimated with improved methods by the injection of a large amount of [1-14C]valine of low specific activity. Protein synthesis activity in the dorsal root ganglia was inhibited to the extent of 60% of the control as early as day 5 and this continued to the symptomatic period (day 15) on which crossing of hind limbs, a typical sign of organomercurial poisoning, was observed in the animals. The sciatic nerves and dorsal roots increased protein synthesis by 56% at the symptomatic period. These increases in protein synthesis may be due to the stimulation of reactivity of Schwann's cells. On the contrary, the protein synthesis in the ventral roots showed a gradual decrease as the intoxication proceeded and decreased to 73% of the control at the symptomatic period, being similar to the case of brain. The double-labeling studies with sodium dodecyl sulfate/polyacrylamide gel electrophoresis exhibited that methylmercury inhibited the synthesis of the dorsal root ganglion proteins non-uniformly in various apparent molecular sizes, especially on day 10.

The inhibitory action of acetaldehyde on the tonic component of the potassium-induced contracture in the guinea-pig taenia caeci

The effect of acetaldehyde on the contractile responses induced by potassium-rich solution was studied in the guinea-pig taenia caeci. Acetaldehyde at a concentration between 1 and 50 mM reduced the tonic contraction induced by a high potassium solution containing a normal concentration of CaCl2 without affecting the phasic one. The phasic contraction was depressed only slightly at a very high concentration of acetaldehyde (100 mM). The tonic component increased with increasing external Ca concentration, and the reduction of this tonic contraction by acetaldehyde was greater at high Ca concentrations. In Ca-free, K-rich solution, carbachol induced a transient contraction. This carbachol-induced contraction in the absence of external Ca was markedly depressed at the second application of carbachol, but it reappeared after exposure to a Ca-containing solution. In this condition acetaldehyde did not affect these carbachol-responses, while it decreased a slow rise of tension during exposure of Ca. These results suggest that acetaldehyde inhibits the entry of external calcium without having an appreciable effect on the release of Ca and on the filling of the internal stores with Ca.

Effects of acetaldehyde on the membrane potential and membrane resistance of the identified neurons in the abdominal ganglion of Aplysia kurodai

Actions of acetaldehyde on membrane potentials and membrane resistances of Aplysia neurons were studied using an intracellular recording and current injection technique. Several functionally different neurons in the abdominal ganglion of A. kurodai were identified on the basis of their morphological and electrophysiological characteristics. Application of between 5 and 50 mM acetaldehyde produced depolarization of the membrane, in all types of cells investigated. This depolarization was accompanied by an increase in the rate of spike discharge. The amplitude and the rates of rise and fall of the action potential were reduced and the duration of the spike was prolonged. Acetaldehyde had no significant effect on the input resistances of ganglion cells. These actions of the aldehyde were observed to be similar in the completely isolated neuron-soma preparation separated from the neighbouring cells or synapses.

Effects of acetaldehyde on the membrane resistance in the smooth muscle of the guinea-pig taenia caecum

The action of acetaldehyde on the membrane resistance of the guinea-pig taenia caecum was investigated with a double sucrose-gap method in different ionic environments. Application of acetaldehyde (10--20 mM) produced hyperpolarization, block of spike discharge and reduction of the membrane resistance. The reduction of the membrane resistance by acetaldehyde was potentiated by increasing the external K+ concentration and by replacement of Cl- with NO3-; it was reduced by lowering the external K+ concentration and by replacement of Cl- with benzenesulfonate. Replacement of NaCl with Tris-Cl, sucrose, or LiCl had no appreciable effect on the action of acetaldehyde on the membrane resistance. It therefore seemed likely that acetaldehyde increased the membrane conductance for K+ and Cl- more than for Na+. Although this action of acetaldehyde was similar to the alpha-action of catecholamine, the decrease of the membrane resistance and hyperpolarization induced by acetaldehyde remained unchanged in the presence of phentolamine.

The action of acetaldehyde on the intracellular electrical activities of the guinea-pig taenia coli

The effect of acetaldehyde on the membrane potential and the membrane resistance of the guinea-pig taenia coli has been studied with an intracellular recording technique. Application of acetaldehyde in the concentration of between 5 and 20 mM produces reduction or elimination of the spontaneous spike activity and hyperpolarization of the membrane. The amplitude and the rates of rise and fall of the action potential are reduced by the drug. The duration of the spike is slightly prolonged. Acetaldehyde also reduces the amplitude of the evoked action potential produced by externally applied cathodal stimulation in twice hypertonic solution. Electronic potentials induced by anodal current are reduced both in size and time course by acetaldehyde during the stage of hyperpolarization.

Effects of acetaldehyde on electrical and mechanical activities of guinea-pig taenia coli

The effect of acetaldehyde on the electrical and mechanical activities of the isolated segment of taenia coli from guinea-pigs has been studied using a sucrose-gap method. Application of acetaldehyde produces relaxation of the muscle, which is accompanied by reduction or cessation of spontaneous spike activity and hyperpolarization of the membrane. The hyperpolarization becomes smaller with lowering the temperature. These actions of acetaldehyde are not modified by adrenergic and cholinergic receptor blocking agents nor by tetrodotoxin and ouabain. Acetaldehyde also reduces the evoked activities produced by KCl, BaCl2, acetylcholine or electrical stimulation. The nonadrenergic inhibitory junction potential is reduced by acetaldehyde. When external Ca++ is replaced with Sr++ or Ba++, the action of acetaldehyde is suppressed. Addition of Mn++ eliminates the action of the aldehyde. Acetaldehyde relaxes the muscle when administered after fully developed membrane depolarization induced by K2SO4.

Demonstration of intracytoplasmic glycogen of megakaryocytes and blood platelets by means of the periodic acid-thiocarbohydrazide-silver proteinate method

The glycogen of megakaryocytes and blood platelets has been investigated in glutaraldehyde and osmium tetroxide fixed tissues by the periodic acid-thiocarbohydrozide-silver proteinate method (PA-TCH-SP). The PA-TCH-SP method involves the staining of intracytoplasmic glycogens more densely than the routine lead citrate method. Glycogen having a mean particle diameter of 21.1 nm has been shown localizing in the matrix of mature megakaryocytes, while that of glycogen in the platelets was 26.2 nm. The staining pattern of the glycogen in blood platelets was classified into three groups according to staining intensity. It is found that the PA-TCH-SP method is a very suitable one for the demonstration of intracytoplasmic glycogen from the viewpoints of reaction specificity, reproducibility, fineness of reaction products, sufficiency of electron density, and experimental cost. This method is also a very useful one for differentiating intracytoplasmic glycogens and ribosomes.