کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4338734 1614883 2011 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
GABAB restrains release from singly-evoked GABA terminals
موضوعات مرتبط
علوم زیستی و بیوفناوری علم عصب شناسی علوم اعصاب (عمومی)
پیش نمایش صفحه اول مقاله
GABAB restrains release from singly-evoked GABA terminals
چکیده انگلیسی

Neurotransmitter release regulation is highly heterogeneous across the brain. The fundamental units of release, individual boutons, are difficult to access and poorly understood. Here we directly activated single boutons on mechanically isolated nucleus tractus solitarius (NTS) neurons to record unitary synaptic events under voltage clamp. By scanning the cell surface with a stimulating pipette, we located unique sites that generated evoked excitatory postsynaptic currents (eEPSCs) or evoked inhibitory postsynaptic currents (eIPSCs) events. Stimulus-response relations had abrupt thresholds for all-or-none synaptic events consistent with unitary responses. Thus, irrespective of shock intensity, focal stimulation selectively evoked either eEPSCs or eIPSCs from single retained synaptic boutons and never recruited other synapses. Evoked EPSCs were rarely encountered. Our studies, thus, focused primarily on the more common GABA release. At most locations, shocks often failed to release GABA even at low frequencies (0.075 Hz), and eIPSCs succeeded only on average 2.7±0.7 successful IPSCs per 10 shocks. Activation of eIPSCs decreased spontaneous IPSCs in the same neurons. The GABAA receptor antagonist gabazine (3 μM) reversibly blocked eIPSCs as did tetrodotoxin (TTX) (300 nM). The initial low rate of successful eIPSCs decreased further in a use-dependent manner at 0.5 Hz stimulation—depressing 70% in 2 min. The selective GABAB receptor antagonist 3-[[(3,4-Dichlorophenyl)methyl]amino]propyl] diethoxymethyl)phosphinic acid (CGP 52432) (5 μM) had three actions: tripling the initial release rate, slowing the use-dependent decline without changing amplitudes, and blocking the shock-related decrease in spontaneous IPSCs. The results suggest strong, surprisingly long-lasting, negative feedback by GABAB receptors within single GABA terminals that determine release probability even in isolated terminals.

▶Activation of single terminals on solitary tract neurons was spatially distinct with sharp fixed, all-or-none thresholds. ▶Yielded either glutamate or GABA release only with GABA terminals more common. ▶Inter-terminal events were homogeneous within subtype. ▶GABA release was low in probability but depressed in control by presynaptic GABAB receptors even without stimulation. ▶Evoked GABA from single terminals inhibited spontaneous release across the neuron.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Neuroscience - Volume 193, 13 October 2011, Pages 54–62
نویسندگان
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