PRINCIPAL INVESTIGATOR(S ) : Torquato Gualtierotti, F. Bracchi, and E. Rocca 



EXPERIMENT TITLE/NUMBER : Orbiting Frog Otolith Experiment (0F0) 



PROGRAM/MISSION : 0F0 



CLASSIFICATION : Animal - Bullfrog ( Rana calestiana ) 



DISCIPLINE(S) : Neurosensory, Behavioral science 



OBJECTIVES : To obtain information concerning the response of the basic 

 acceleration sensor mechanism (hair cells of the otolith organ) to 

 weightlessness. 



PROTOCOL : Two bull frogs were completely immersed in water. Action 

 potentials were recorded from four vestibular nerve fibers corresponding to 

 the gravity sensors of the inner ear. A centrifuge built into the experiment 

 capsule subjected the sensors to a range of 10 g during weightlessness and 

 periodically up to 0.6g of stimulation. 



EQUIPMENT : Neutral-buoyancy electrodes, ECG electrodes, Frog Otolith 

 Equipment Package (consisting of spin motor, anit-vibration mounts, multipass 

 gas exchanger, evaporator, thermostatic valve, water supply, oxygen reservoir, 

 C0 ? absorber, amplifiers, and spacecraft data handling system). 



RESULTS : During the first few days of weightlessness, the otolith showed 

 1) fluctuation of the activity at rest up to 20 times larger than on the 

 ground, 2) a change of gain and mode of the responses to the centrifuge spin 

 cycles; the mode changed from tonic to phasic and vice versa. The change 

 1) gradually disappeared in 4-5 days, the activity at rest returning to 

 normal. The change 2) was maintained throughout the flight not showing trend 

 to normalization. 



CONCLUSIONS : Shows an indication of an only partial adaptation of a basic 

 neural control process to weightlessness while some alteration remains. 

 (Revealed partial adaptation process at the basic receptor level of living 

 organisms to weightlessness) . 



PUBLICATIONS : 87, 231, 232, 233, 234, 235, 236, 237, 238 



108 



