Nerves from spider crabs anid squid fluoresce when staiined with Acridine Orange. The intenisity of fluorescence increases during nerse conduction. Prolongation of the electric response in the squid axon is associated with a fluorescence change of similar duration. These findings suggest that the physicochemical properties of the macromolecules around the dye molecules in the nerve membrane drastically change during the process of nerve conduction.

Acridines↗

PubMed1969

Binding of adenosine 5'-monophosphate and substrate by rabbit liver fructose 1,6-diphosphatase.

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Adenine Nucleotides↗

PubMed1969

Transient changes in extrinsic fluorescence of nerve produced by electric stimulation.

NERVES STAINED WITH ONE OF THE FOLLOWING FLUOROCHROMES WERE FOUND TO RESPOND TO ELECTRIC STIMULATION WITH TRANSIENT CHANGES IN THE FLUORESCENT LIGHT: acridine orange, acridine yellow, 8-anilinonaphthalene-1-sulfonate, auramine O, 1-dimethylaminonaphthalene-5-sulfonyl chloride, fluorescein isothiocyanate, LSD, pyronin B, pyronin Y, rhodamine B, rhodamine G, rose bengal, and 2-toluidinylnaphthalene sulfonate. The properties of covalently bonded fluorochromes in the nerve and the behavior of fluorochromes introduced into the axon interior were studied. By measuring fluorescence polarization, direct evidence was obtained showing a decrease in intramembrane viscosity during the action potential.

Acridines↗

PubMed1969

Acceleratory synapses on pacemaker neurons in the heart ganglion of a stomatopod, Squilla oratoria.

The pacemaker neurons of the heart ganglion are innervated from the CNS through two pairs of acceleratory nerves. The effect of acceleratory nerve stimulation was examined with intracellular electrodes from the pacemaker cells. The major effects on the pacemaker potential were an increase in the rate of rise of the spontaneous depolarization and in the duration of the plateau. The aftereffect of stimulation could last for minutes. No clear excitatory postsynaptic potential (EPSP) was observed, however. On high frequency stimulation, a small depolarizing response (the initial response) was sometimes observed, but the major postsynaptic event was the following slow depolarization, or the enhancement of the pacemaker potential (the late response). With hyperpolarization the initial response did not significantly change its amplitude, but the late response disappeared, showing that the latter has the property of the local response. The membrane conductance did not increase with acceleratory stimulation. The injection of depolarizing current increased the rate of rise of the spontaneous depolarization, but only slightly in comparison with acceleratory stimulation, and did not increase the burst duration. It is concluded that the acceleratory effect is not mediated by the EPSP but is due to a direct action of the transmitter on the pacemaker membrane.

Animals↗