Article Figures & Data
Figures
- Figure 1.
Morphological analysis of synaptically connected pairs of GP neurons. A, Digital image of two biocytin filled and stained GP neurons in a brain slice. Arrow marks the location of a putative synaptic connection. B, Enlargement of the location of the putative synaptic connection. C, A Neurolucida reconstruction of the pair of cells in A. Black, presynaptic soma and dendrites; green, presynaptic axon; red, postsynaptic soma and dendrites; blue, postsynaptic axon. Arrow indicates location of the putative synaptic connection (emphasized by filled pale blue circle). D, Schematic drawing of the GP and surrounding brain areas. The locations of the five paired recordings are marked by filled circles.
- Figure 2.
Presynaptic APs generate unitary IPSPs in GP neurons. A, Representative recording of a presynaptic AP aligned with 10 consecutive traces of the postsynaptic membrane potential. B, Representative recording of a presynaptic AP aligned to an average of 40 consecutive traces of the postsynaptic membrane potential. Addition of 50 μm bicuculline eliminated the IPSP (bottom trace, also an average of 40 membrane potential traces).
- Figure 3.
STD of unitary GP synapses. A, Average of 30 consecutive traces of postsynaptic membrane potentials generated following presynaptic stimulation with a train of five APs at 10 Hz (top trace) or five APs at 40 Hz (bottom trace). B, The ratio of the nth IPSP in the train to the first IPSP was plotted as a function of the number of the AP in the train. ○, two synapses stimulated at 10 Hz; ●, two synapses stimulated at 40 Hz. Smooth lines are exponential curve fits to each dataset. C, Steady-state depression values extracted from curve fits similar to those in B plotted as a function of the frequency of the presynaptic AP train. Error bars indicate the least-square error of the exponential curve fit in B.
- Figure 4.
A unitary inhibitory synaptic connection can modulate postsynaptic firing of a GP neuron. A, Representative plot of presynaptic and postsynaptic membrane potential when a 40 s train of 40 Hz was generated in the presynaptic neuron. The presynaptic neuron was hyperpolarized by a −25 pA current injection. The postsynaptic membrane potential trace is shown expanded at the beginning and end of stimulation to emphasize the change in firing frequency. B, Presynaptic (top) and postsynaptic (bottom) averages using the presynaptic APs as the trigger calculated for the whole stimulation period. C, The presynaptic (top) and postsynaptic (bottom) spike-triggered average calculated for the last 40 s of the stimulus. D, Mean postsynaptic firing rate (n = 3) normalized to the mean prestimulation rate. Dashed lines, ±1 STD of firing frequency before stimulus onset; solid line, average firing frequency before stimulus onset. Vertical dotted lines mark beginning and end of stimulation. E, Peristimulus time histogram of the postsynaptic neuron (n = 3) aligned to the stimulation pulses and normalized to the prestimulation mean firing rate. Dashed lines mark ±1 STD of firing frequency before stimulus onset.
