title: Input-output dependence reveals the components of GABAergic modulation in rat hippocampal CA3 in vivo.
abstract: Field population spikes, orthodromically elicited (PS2), upon commissural stimulation, in the hippocampal CA3 region of the anaesthetized rat, were determined at stimulation intensities (Istim) varying from 0.25 to 6 mA. A sharp, stimulation-dependent increase in the PS2 amplitude was observed with increasing Istim up to 0.5 mA, followed by an exponential decrease in PS2 at higher Istim, reaching a steady value with Istim above 3 mA. Intravenous (iv) infusion of bicuculline (BIC) increased the PS2, when elicited by Istim between 0.25 and 6 mA, though the stimulus-response (S-R) curve consistently presented a local minimum in between 0.5 to 1 mA. Baclofen (10 and 30 mg/kg iv) dose-dependently reduced PS2 at the lowest Istim (0.25 mA), both in control and in BIC-treated animals. At higher stimulation intensities, however, baclofen (30 mg/kg iv) increased PS2, while barely affecting the population spike in BIC-treated animals. The input-output dependence of this CA3 response appeared able to provide a convenient in vivo model revealing the components of GABAergic modulation.
authors.affiliation: UCB S.A. Pharma Sector, Research & Development, Braine-l'Alleud, Belgium.
authors.forename: D G
authors.initials: DG
authors.lastname: Margineanu
authors.forename: E
authors.initials: E
authors.lastname: Wülfert
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D018755:GABA Agonists; D018756:GABA Antagonists; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D001640:Bicuculline