title: Metabolic regulations of the rhythmic activity in pacemaker neurons. III. Neutralization of the pentylenetetrazol effect in regularly beating Aplysia neurons by metabolic modifiers.
abstract: 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.
mesh_terms: 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
chemical_list: D002951:Citrates; D005636:Fructosephosphates; D005988:Glyceric Acids; D000255:Adenosine Triphosphate; D010424:Pentobarbital; D010433:Pentylenetetrazole; D010634:Phenobarbital