Cross-Modal Plasticity And Cellular Mechanisms In Terms Of The Upregulation Of Olfaction Induced By A Lack Of Whisker Tactile Input

Objective: In order to investigate cellular mechanism underlying cross-modal plasticity,we establish a mouse model that lack of whisker tactile input induces the upregulationof olfaction, and analyze dynamic changes in the encoding ability of sequential spikes atthe GABAergic and pyramidal neurons of piriform cortex after vibrissae impairment.Methods:1) The deprivation of whisker input in mice: The vibrissaes of mouse pups onthe right side of snout were clipped at <1mm in length every48hours, starting fromage PND12up to PND19.2) Seven days after procedure, we tested mouse’s olfactoryfunction in T maze, in which the successful rate of moving toward food direction wasused to identify olfactory function and upregulation.3) Patch-clamp experiments: Thecortical slices including piriform cortex (400m) were quickly sectioned from mice aweek after their whisker input deprivation. The slices were then held in the oxygenatedartificial cerebrospinal fluid (ACSF) at25C for1-2hours. A slice was transferred to asubmersion chamber and perfused with oxygenated ACSF at31C. With an Axoclamp-200B amplifier, we recorded spike patterns (e.g., inter-spike intervals) and intrinsicproperties (e.g., threshold potentials and absolute refractory periods) of GFP-labeledGABAergic neurons and pyramidal neurons in piriform cortex under DIC/fluorescentmicroscopy (Nikon E600-FN). The electrical signals were acquired with Clampex andanalyzed with Clampfit.Results:1) The successful rates of judging food location in mice with the whisker inputdeprivation showed higher than those in control mice.2) Compared with control groups,spike capacity (merited by inter-spike intervals) at the GABAergic neurons of piriformcortex from mice with whisker deprivation was significantly decreased (P<0.05). Suchchanges were associated with a prolongation of absolute refractory periods (P<0.05) andan increase of threshold potentials (P<0.05). On the other hand, pyramidal neurons inwhisker deprivation mice showed the significant increases in spike capacity (P<0.05) aswell as the reduction of absolute refractory periods (P<0.05) and threshold potentials(P<0.01), compared with controls. Conclusion:1) Whisker input deprivation upregulates olfactory function in mice.2) Animpairment of whisker inputs weakens the function of GABAergic cells and enahancesthat of pyramidal cells in piriform cortex. The high excitability of neural network in thisarea may contribute to the incease of olfactory sensitivity in the cross-model plasticityin terms of olfactory upregulation induced by a lack of whisker tactile input.