Transcranial focused ultrasound to the thalamus alters anesthesia time in rats

Abstract

A pulsed application of focused ultrasound (FUS) to the regional brain tissue alters the state of tissue excitability and thus provides the means for noninvasive functional neuromodulation. We report that the application of transcranial FUS to the thalamus of anesthetized rats reduced the time to emergence of voluntary movement from intraperitoneal ketamine/xylazine anesthesia. Low-intensity FUS was applied to the thalamus of anesthetized animals. The times required for the animals to show distinct physiological/behavioral changes were measured and compared with those times required in a control session without sonication. The sonication significantly reduced the time to show pinch response and voluntary movement. The modulatory effects of FUS on anesthesia suggest potential therapeutic applications for disorders of consciousness such as minimally consciousness states.

Figures

Figure 1

(A) Experimental setup. The animal's head is coupled to an (a) ultrasound transducer by a (b) bag containing degassed water. The (c) heat pad regulated the temperature while the (d) optical imaging system provided the stereotactic guidance to the thalamus. (B) Illustration of the sonication setup (not drawn to scale).

Figure 2

A comparison box plot indicating the range, first/third quarter percentile, and the mean of the time to reach the measured physiological parameters after the onset of effective anesthesia. FUS was applied from 40 to 60 min after the onset of anesthesia (indicated with dashed lines). White boxes: control condition (denoted by `CN') without sonication, gray boxes: FUS sonication (noted as `FUS'). Acronyms for the parameter; RR increase: increase in respiratory rate, Rapid RR: rapid and irregular respiration, Whisker M: movement of the whisker, Eye blink R: response to the air puff to the eyes, Pinch R: response to the hind-paw pinching, Full M: the onset of the voluntary movement. *: marginal significance (p=0.06), **: significance (p<0.005)