DECRO System for Enhanced Circadian Rhythm Phenotyping in Rats

Abstract

Circadian phenotyping in rodents is usually established by actogram plotting using a variety of non-invasive setups (software and hardware). In neuroscience research field, monitoring of circadian rhythm can be useful and informative and, in some circumstances, combining cardiorespiratory parameters to this actogram can become an added value. However, this combination implies that the setups become either invasive (telemetry implant) or restraining (plethysmography). DECRO™ system has been developed to refine the implementation of this combination in a non-invasive and a non-restraining manner.

Data from 8 Sprague Dawley rats (229-256 g), used in a safety pharmacology study, were reanalysed to assess the ability of DECRO system to detect circadian rhythms for several vital functions. Rats were pair-housed with a 12-hour Light/Dark cycle were divided in two groups (Vehicle and Baclofen 15 mg/kg P.O.). Heart Rate (HR), Respiratory Rate (RR) and Activity Level (AL) were recorded over 24 hours using a DECRO Bluetooth-based, external jacketed telemetry device. Data were averaged for the 12-hour light/dark periods.

In the vehicle group, the AL during the dark period (active period for rats) was found significantly higher (p<0.05) than during the light period (+22 mg / +133%). HR and RR followed the same trend (+33 bpm / +8%; +9 bpm / +6%; respectively).
In the baclofen group, the signature of the circadian rhythm was altered by the pharmacological effect of the compound (activity depressant). Indeed, although the AL increased during the dark period, its magnitude was lower than in the control group.

We provide evidence that the DECRO system can detect activity level and cardiorespiratory changes whether being related to circadian rhythm or to a test compound. Moreover, this approach is in line with the 3R rule by its non-invasiveness and can be considered as an added value for neuroscientists.