Endogenous anticonvulsant mechanisms represent a reliable and currently underdeveloped strategy against recurrent seizures and may recall novel original therapeutics. Here, we investigated whether the intensification of the astroglial Glu-GABA exchange mechanism by application of the GABA precursor putrescine (PUT) may be effective against convulsive and non-convulsive seizures. We explored the potential of PUT to inhibit spontaneous spike-and-wave discharges (SWDs) in WAG/Rij rats, a genetic model of absence epilepsy. Significant shortening of SWDs in response to intraperitoneally applied PUT has been observed, which could be antagonized by blocking GAT-2/3-mediated astrocytic GABA release with the specific inhibitor SNAP-5114. Direct application of exogenous GABA also reduced SWD duration, suggesting that PUT-triggered astroglial GABA release through GAT-2/3 may be a critical step in limiting seizure duration. PUT application also dose-dependently shortened seizure-like events (SLEs) in the low-[Mg²⁺] in vitro model of temporal lobe epilepsy. SNAP-5114 reversed the antiepileptic effect of PUT in the in vitro model as well, further confirming that PUT reduces seizure duration by triggering glial GABA release. In accordance, we observed that PUT specifically reduces the frequency of excitatory synaptic potentials, suggesting that it specifically acts at excitatory synapses. We also identified that PUT specifically eliminated the tonic depolarization-induced desynchronization of SLEs. Since PUT is an important source of glial GABA and we previously showed significant GABA release, it is suggested that the astroglial Glu-GABA exchange mechanism plays a key role in limiting ictal discharges, potentially opening up novel pathways to control seizure propagation and generalization.

Glial mechanisms regulate neuronal excitability through multiple mechanisms, including the control of extracellular inhibitory signaling. One such mechanism is the Glu/GABA exchange process, in which glutamate uptake is coupled to GABA release, with GABA being synthesized from the polyamine putrescine, placing putrescine at a central position in metabolic pathways that may influence epileptiform activity. Here, we examined how pharmacological manipulation of key enzymes of putrescine metabolism affects seizure-like activity in the low-[Mg²⁺] in vitro model of frontotemporal epilepsy, complemented by in vivo recordings in the non-convulsive absence epilepsy model Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. Increasing putrescine availability by inhibiting spermidine synthase with trans-4-methylcyclohexylamine significantly reduced both the duration and appearance of seizure-like events. Strikingly, simultaneous inhibition of monoamine oxidase B (MAO-B) and diamine oxidase (DAO) with deprenyl and aminoguanidine almost completely abolished seizure-like events in vitro and markedly suppressed spike–wave discharges in WAG/Rij rats. This effect was largely reversed by blockade of GAT-2/3 transporters with SNAP-5114, suggesting the presence and significant anti-epileptic potential of a MAO-B- and DAO-independent putrescine–GABA synthesis pathway. Together, these findings indicate that the anticonvulsant effects of putrescine metabolism arise from the coordinated engagement of multiple parallel pathways rather than from a single dominant enzymatic route. Putrescine thus appears to function as a metabolic hub whose increased availability can be channeled into several anticonvulsant processes, suggesting that therapeutic strategies enhancing putrescine-dependent inhibitory pathways at the network level may offer promising avenues for the modulation of epileptiform activity.