Subtypes of muscarinic acetylcholine receptors involved in the persistent activity of layer V pyramidal neurons in the primary auditory cortex of young mice / 生理学报

Cholinergic receptor activation and intracellular current injection lead to the persistent activity (PA), which may be involved in inducing neural plasticity. Our previous study showed that PA is closely related to the activation of muscarinic acetylcholine receptors (mAChRs) in pyramidal neurons of mouse primary auditory cortex (AI). However, the subtypes of mAChRs involved in PA remain unclear. Thus, using whole-cell patch-clamp recording and pharmacological methods, we investigated the role of different mAChR subtypes in inducing PA in AI layer V pyramidal neurons of young mice. The results showed that activation of mAChRs with intracellular depolarizing current induced PA in layer V pyramidal neurons. Blockade of M1, M2 or M3 subtypes prevented the PA, whereas M4 receptor antagonists did not affect the production of PA. The results suggest that the PA may be induced through a mechanism involving M1, M2 and M3 muscarinic receptors, but not M4 subtype.

In vitro whole-cell patch clamp recordings of neurons in subnuclei of mouse inferior colliculus / 生理学报

The inferior colliculus (IC) is a pivot along the central auditory pathway. Using infrared visual whole-cell patch clamp recording technique, we investigated the electrophysiological properties of IC subnuclei neurons. Recordings were made from 88 neurons, including 21 neurons from the dorsal cortex of the IC (ICd), 43 neurons from the central nucleus of the IC (ICc) and 24 neurons from the external cortex of the IC (ICx). Based on the responses to positive current injection, three firing patterns, i.e., onset (6.8%, n = 6), adapting (39.8%, n = 35) and sustained (53.4%, n = 47) patterns, were identified. The hyperpolarization-activated inward current (Ih) could be recorded in half of the neurons (49/88). The sustained pattern occurred in more than half of ICd and ICc neurons (61.9% and 67.4%), while the adapting pattern occurred in majority of ICx neurons (75%). Action potential (AP) threshold and time constant also showed significant differences across neurons from the ICd, the ICc and the ICx. Our results indicate that IC neurons are different in electrophysiological properties across the subnuclei. The variance of the responses may be related to the distinct types of neurons as well as the received projections, which is implicated in the distinct roles of IC neurons in central auditory processing.