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Extracellular bromide enhances GABAA receptor function in the immature, but not the adolescent rat pilocarpine

Heiner Kolp1, Jana K Hackert1, Marco Heerdegen1

  • 1Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany.

Epilepsy Research
|March 2, 2025
PubMed

Insights

Immature rats treated with pilocarpine showed enhanced GABAergic inhibition with bromide, unlike adolescent rats. This suggests immature models are crucial for developing infant epilepsy therapies.

Area of Science:

  • Neuroscience
  • Epilepsy Research
  • Pharmacology

Background:

  • Status epilepticus (SE) is a neurological emergency characterized by prolonged seizures.
  • Pilocarpine-induced SE is a standard model for studying epilepsy in rodents.
  • The effects of bromide on GABAergic neurotransmission may differ between immature and adult brains.

Purpose of the Study:

  • To investigate the impact of extracellular bromide on GABAergic neurotransmission in a novel immature rat pilocarpine model.
  • To compare these effects with those observed in a standard adolescent rat pilocarpine model.
  • To evaluate the potential of immature models for epilepsy research.

Main Methods:

  • An immature rat model was established using repetitive pilocarpine administration (340 mg/kg on postnatal days 9, 11, 15).
  • Electrophysiological recordings of Schaffer collateral CA1-synapse and CA1 pyramidal neurons were conducted in 30-70 day-old animals.
  • Extracellular bromide (20 mM) was introduced by replacing NaCl with NaBr in the bath solution, and findings were compared to an adolescent model (single pilocarpine dose on postnatal day 30).

Main Results:

  • Extracellular bromide significantly enhanced the GABAA-receptor component of inhibitory postsynaptic potentials in the immature model.
  • Bromide application led to hyperpolarization of the GABAA-receptor reversal potential and reduced intrinsic neuronal excitability in immature rats.
  • Long-term potentiation, induced by high-frequency stimulation, remained unaffected by bromide in both immature and adolescent models.

Conclusions:

  • The immature rat model demonstrated persistent bromide-enhanced GABAA-receptor function and reduced excitability, effects not observed in the adolescent model.
  • These findings highlight the distinct neurophysiological characteristics of immature brains in response to pilocarpine and bromide.
  • Immature animal models are essential for exploring novel therapeutic strategies targeting infantile epilepsies.
Abstract

Keywords:
ExtracellularGamma-amino butyric acidIntracellularPhasic inhibitionTonic inhibition

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