Wireless Monitoring of Circadian Rhythms

Pre-calibrated radio-telemetric transmitters (G2 E-Mitters; Starr Life Sciences; Oakmont, PA, USA) which transmit locomotor activity (LMA) and core body temperature (T_b) were implanted i.p. under surgical anesthesia (dexdomitor, 1 mg/kg; ketamine, 75 mg/kg). Identical surgical procedures were performed inside the sterile environment for GF and ex-GF mice, and under aseptic conditions for SPF mice^{32 (link)}. The anti-sedative atipamezole (5 mg/kg) was administered after surgery, and buprenorphine (0.1 mg/kg, s.c.) analgesic was administered immediately after surgery and at 12 h intervals thereafter for 48 h. Receiver boards (ER-4000 Energizer/Receiver; Starr Life Sciences) positioned under animal cages acquired T_b and LMA data at 1 min intervals using VitalView software (Starr Life Sciences). This methodology permitted measurement of LMA and T_b over indefinite time spans (i.e., multiple months) with sampling intervals sufficient for Fourier-based time series analysis of circadian activity and temperature rhythms, in contrast with other efforts^{32 (link),47 (link),48 (link)} which have been limited to brief intervals (≤ 5 days) and/or aggregate measures of total activity binned hourly or daily, inadequate for the quantitative evaluation of circadian behavioral rhythms.