Metabolic regulations of the rhythmic activity in pacemaker neurons. III. Neutralization of the pentylenetetrazol effect in regularly beating Aplysia neurons by metabolic modifiers.
In regular beating pacemaker neurons isolated from the sea hare Aplysia californica, 30-50 mM pentylenetetrazol (PTZ) induces spike doublets and triplets, multi-spike bursts, and paroxysmal depolarizing shifts. The development of the characteristic PTZ-induced changes in impluse pattern is preceded by a transient increase in discharge frequency and a reduction in after-hyperpolarization. According to earlier findings, the rhythmic spike activity of pacemaker neurons is governed by a phosphofructokinase-fructose-1,6-diphosphatase-mediated substrate cycle, the activation of which leads to the appearance of spike bursts. Inhibitory modifiers of this neuronal substrate cycle, such as citrate, ATP, and 3-phosphoglycerate, are able to neutralize the changes in the impluse characteristics occurring as the result of PTZ action. Since the reinitiated single-spike trains reverted again to the PTZ pattern following the further addition of activating modifiers, such as fructose-1,6-diphosphate or fructose-6-phosphate, it appears likely that PTZ exerts an influence on the metabolic reactions driving the rhythmic spike activity. In contrast to the reversible effects of the metabolic modifiers the conventional anti-convulsants, phenobarbital and pentobarbital, merely block all spike activity.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002951:Citrates / Q000494:pharmacology; D005636:Fructosephosphates / Q000494:pharmacology; D005724:Ganglia / Q000187:drug effects* / Q000378:metabolism; D005988:Glyceric Acids / Q000494:pharmacology; D008974:Mollusca / Q000502:physiology*; D010424:Pentobarbital / Q000494:pharmacology; D010433:Pentylenetetrazole / Q000494:pharmacology*; D010507:Periodicity; D010634:Phenobarbital / Q000494:pharmacology
D002951:Citrates; D005636:Fructosephosphates; D005988:Glyceric Acids; D000255:Adenosine Triphosphate; D010424:Pentobarbital; D010433:Pentylenetetrazole; D010634:Phenobarbital