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. Author manuscript; available in PMC: 2007 Jan 10.
Published in final edited form as: Neuron. 2006 Dec 7;52(5):883–896. doi: 10.1016/j.neuron.2006.10.010

Figure 6.

Figure 6

The EPSP/IPSP Sequences in the Cortical and Thalamic Inputs to the LA neuron. (A) Response of a cell in the LA to prolonged depolarizing current injection. Significant spike frequency accommodation observed in the recorded cell indicates that it is a pyramidal neuron. (B) Biphasic synaptic response recorded under current-clamp conditions in the LA neuron at -55 mV (control) in response to stimulation of cortical input. It consisted of the initial EPSP that was followed by the PTX-sensitive IPSP. A second trace (PTX) depicts an isolated EPSP when the IPSP was blocked with PTX. (C) The ESPS/IPSP sequence (control) was blocked by CNQX (20 μM), indicating the IPSP is disynaptic. (D) A schematic representation of the neural circuit for the EPSP/IPSP sequences in the LA. IN, interneuron; PN, principal neuron. (E) The EPSP/IPSP sequences recorded in cortical input over a range of membrane potentials (from -110 mV to -50 mV). Each trace represents the average of 10 responses. Dashed line marks the peak amplitude of the IPSP. (F) Dependence of the IPSP amplitude on membrane potential when responses were evoked either at cortical (n = 6) or thalamic pathway (n = 6). Values for the graph were obtained by normalizing the peak IPSP amplitude at each membrane potential to the amplitude of the IPSP recorded at -50 mV. Reversal potential of the IPSP was -71.3 ±4.0 mV (n = 6) and -72.1 ±3.7 mV (n = 6) in cortical and thalamic inputs, respectively (no significant difference between inputs, p = 0.89).