The effects of GABA and glutamate, their ionotropic agonists and antagonists on hydras ectodermal and endodermal pacemaker systems were studied. GABA decreased ectodermal body contraction-bursts (CBs) and the number of pulses in a burst (P/CB) and endodermal rhythmic potentials (RPs); tentacle pulses (TPs) were not affected. The GABAA agonist, muscimol and the benzodiazapine receptor agonist, diazepam, mimicked the effects of GABA on the endodermal system. The GABAA antagonist, bicuculline, counteracted GABAs effects. Low concentrations of glutamate increased CBs, and RPs. Higher concentrations required Con A to produce the same effect on CBs and P/CB. TPs were increased by high concentrations of glutamate and kainate. The ionotropic glutamate agonist, AMPA also required Con A to increase CBs and RPs. The effects of AMPA were antagonized by NBQX, which, per se, decreased CBs. The results indicate that GABA and glutamate, acting on their ionotropic receptors, modify the impulses of hydras pacemaker systems. On the whole GABA decreased the outputs of both ectodermal and endodermal impulse generating systems, while glutamate increased them.
GABA and glutamate receptors are involved in modulating pacemaker activity in hydra
Pierobon P
2003
Abstract
The effects of GABA and glutamate, their ionotropic agonists and antagonists on hydras ectodermal and endodermal pacemaker systems were studied. GABA decreased ectodermal body contraction-bursts (CBs) and the number of pulses in a burst (P/CB) and endodermal rhythmic potentials (RPs); tentacle pulses (TPs) were not affected. The GABAA agonist, muscimol and the benzodiazapine receptor agonist, diazepam, mimicked the effects of GABA on the endodermal system. The GABAA antagonist, bicuculline, counteracted GABAs effects. Low concentrations of glutamate increased CBs, and RPs. Higher concentrations required Con A to produce the same effect on CBs and P/CB. TPs were increased by high concentrations of glutamate and kainate. The ionotropic glutamate agonist, AMPA also required Con A to increase CBs and RPs. The effects of AMPA were antagonized by NBQX, which, per se, decreased CBs. The results indicate that GABA and glutamate, acting on their ionotropic receptors, modify the impulses of hydras pacemaker systems. On the whole GABA decreased the outputs of both ectodermal and endodermal impulse generating systems, while glutamate increased them.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.