Search

In vivo loose patch and breakthrough whole-cell recordings are useful tools for investigating the intrinsic and synaptic properties of neurons. However, the correlation among pipette resistance, seal condition, and recording time is not thoroughly clear. Presently, we investigated the recording time of different pipette resistances and seal conditions in loose patch and breakthrough whole-cell recordings. The recording time did not change with pipette resistance for loose patch recording ( R p -loose) and first increased and then decreased as seal resistance for loose patch recording ( R s -loose) increased. For a high probability of a recording time ≥30 min, the low and high cutoff values of R s -loose were 21.5 and 36 MΩ, respectively. For neurons with R s -loose values of 21.5-36 MΩ, the action potential (AP) amplitudes changed slightly 30 min after the seal. The recording time increased as seal resistance for whole-cell recording ( R s -tight) increased and the zero-current membrane potential for breakthrough whole-cell recording (MP zero-current ) decreased. For a high probability of a recording time ≥30 min, the cutoff values of R s -tight and MP zero-current were 2.35 GΩ and -53.5 mV, respectively. The area under the curve (AUC) of the MP zero-current receiver operating characteristic (ROC) curve was larger than that of the R s -tight ROC curve. For neurons with MP zero-current values ≤ -53.5 mV, the inhibitory or excitatory postsynaptic current amplitudes did not show significant changes 30 min after the seal. In neurons with R s -tight values ≥2.35 GΩ, the recording time gradually increased and then decreased as the pipette resistance for whole-cell recording ( R p -tight) increased. For the high probability of a recording time ≥30 min, the low and high cutoff values of R p -tight were 6.15 and 6.45 MΩ, respectively. Together, we concluded that the optimal R s -loose range is 21.5-36 MΩ, the optimal R p -tight range is 6.15-6.45 MΩ, and the optimal R s -tight and MP zero-current values are ≥2.35 GΩ and ≤ -53.5 mV, respectively. Compared with R s -tight, the MP zero-current value can more accurately discriminate recording times ≥30 min and <30 min., (Copyright © 2020 Yan, Fang, Zhang and Huang.)

In auditory-conditioned fear learning, the freezing response is independent of the sound frequencies used, but the frequency of the conditioned sound is considered distinct from those of unrelated sounds based on electrophysiological responses in the auditory system. Whether an emergent discriminative learning underlies auditory fear conditioning and which nuclei and pathways are involved in it remain unclear. Using behavioral and electrophysiological assays, we found that the response of medial prefrontal cortex (mPFC) neurons to a conditioned auditory stimulus (CS) was enhanced relative to the response to unrelated frequencies (UFs) after auditory fear conditioning, and mice could distinguish the CS during multifrequency testing, a phenomenon called emergent discriminative learning. After silencing the mPFC with muscimol, emergent discriminative learning was blocked. In addition, the pure tone responses of mPFC neurons were inhibited after injection of lidocaine in the ipsilateral primary auditory cortex (A1), and the emergent discriminative learning was blocked by silencing both sides of A1 with muscimol. This study, therefore, provides evidence for an emergent discriminative learning mediated by mPFC and A1 neurons after auditory fear conditioning. [ABSTRACT FROM AUTHOR]