Skip to main content
. Author manuscript; available in PMC: 2013 Feb 28.
Published in final edited form as: Adv Exp Med Biol. 2012;740:603–638. doi: 10.1007/978-94-007-2888-2_27

Figure 5. Activation of TM α7 nAChRs by 10 µM choline plus 1 µM PNU-120596 enhances spontaneous firing of TM neurons in current-clamp.

Figure 5

The spontaneous firing of TM neurons was native as current injections were not applied (i.e., 0 pA). Horizontal bars indicate −65 mV. In current-clamp, in the absence of PNU-120596 and choline, TM neurons exhibited regular patterns of spontaneous firing (A). In these control experiments, when the membrane voltage was hyperpolarized to −65 mV by injections of a small current, step-like depolarizations were not observed (B). Recordings in A and B were obtained from the same TM neuron 1 min apart. After the sustained repetitive activation of TM nAChRs was observed in voltage-clamp upon administration of 10 µM choline plus 1 µM PNU-120596 (C), current-clamp recordings were conducted using the same TM neuron (D). In current clamp, activation of TM α7 nAChRs resulted in transient repetitive increases in the frequency of spontaneous firing of TM neurons (D, filled arrows). Traces shown in C and D were obtained from the same TM neuron 1 min apart. The framed insert in D) illustrates at a higher time resolution a portion of recording containing one transient excitation. E) The effects of individual step-like depolarizations in current clamp. When a hyperpolarizing current (~ −40 pA) was injected in the recorded TM neuron (the injection time is marked by *) during a prolonged interval of increased frequency (the interval between open and filled triangles), it resulted in cessation of spontaneous firing, allowing detection of the final portion of an underlying step-like depolarization. Therefore, a prolonged depolarization was observed as both an increase in spontaneous firing in the beginning of depolarization (open triangle) and a depolarizing step at the end of depolarization (filled triangle). Subsequent step-like depolarizations are also seen between the two dashed lines in insert. The insert illustrates this transition process at a higher resolution. In these experiments, ACSF contained 20 µM, gabazine, 15 µM DNQX, 50 µM AP-5 and 40 µM picrotoxin. The internal solution was K-gluconate-based. Reprinted from (34) with permission from ASPET.