title: Spontaneous synaptic transmission in dissociated Meynert neurons with the attached synaptic boutons.
abstract: 1. Neurons acutely dissociated from the nucleus basalis of Meynert of adult rats showed spontaneous currents with rapid onset and slow decay under the whole-cell patch-clamp recording. 2. The current had the reversal potential close to the theoretical Cl- equilibrium potential (ECl) and was suppressed by 2 x 10(-6) M bicuculline and 3 x 10(-6) M strychnine. 3. The spontaneous current was suppressed reversibly in the Ca(2+)-free solution containing either EGTA or BAPTA (5 mM). The enhancement of the frequency and amplitude of the current was observed with elevated extracellular K+ concentration, which was also suppressed in the presence of the Ca(2+)-free solution. 4. Nicardipine, a blocker of voltage-dependent Ca2+ channels, had an inhibitory effect as well. 5. A selective GABAB agonist, baclofen, blocked the spontaneous current, whereas a selective antagonist, phaclofen, potently enhanced the current. 6. It is concluded that the observed spontaneous current was a spontaneous inhibitory postsynaptic current (IPSC) due to the release of GABA from the attached synaptic boutons. The release was suppressed by a GABAB receptor activation, indicating that the GABAB receptor regulates the release of GABA from nerve terminals and acts as a negative autoreceptor.
authors.affiliation: Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Harata
authors.forename: S
authors.initials: S
authors.lastname: Ueno
authors.forename: M
authors.initials: M
authors.lastname: Munakata
authors.forename: N
authors.initials: N
authors.lastname: Akaike
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D018118:Chloride Channels; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000187:drug effects; D008566:Membranes / Q000378:metabolism; D009474:Neurons / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism; D009529:Nicardipine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism; D013331:Strychnine / Q000494:pharmacology; D013377:Substantia Innominata / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018118:Chloride Channels; D008565:Membrane Proteins; D018377:Neurotransmitter Agents; D011963:Receptors, GABA-A; D004533:Egtazic Acid; D005680:gamma-Aminobutyric Acid; D009529:Nicardipine; D013331:Strychnine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium; D001640:Bicuculline