Recovery time after intra-abdominal transmitter placement for telemetric (neuro)physiological measurement in freely moving common marmosets (Callitrix jacchus).

Abstract

Background Telemetry is very important for monitoring physiological functions in awake and freely moving laboratory animals. Although implantable transmitters reduce stress resulting from daily handling and restraint, the procedure requires invasive surgery, which affects behaviour and wellbeing of animals. This aspect is important in cases in which behaviour is used as one of the read-out parameters for studying the progression of a disease and/or the effects of a treatment over time. In mice, implantation of telemetric devices shows changes in body weight, locomotor and eating behaviour, and grooming and immobility activities. In contrast to mice, no specific research has been reported in larger animals. Therefore, effect on motor activity, health status and bodyweight after surgical placement of intra-abdominal transmitter, electroencephalogram (EEG) electrodes and electromyogram (EMG) electrodes in common marmosets (Callithrix jacchus) were assessed. Two behavioural test systems for locomotor function were used: the Hourglass test to measure the time a monkey needs to return to its normal upright position, and the Tower test to measure jumping behaviour. Additionally, health status and bodyweight were monitored daily from 2 weeks pre surgery until 49 days post surgery. Results Compared to baseline values, the surgery or the physical presence of the transmitter caused an increase in time needed to achieve an upright position in the Hourglass test. Recovery to baseline values was observed within 8 days post surgery. For the Tower test, the total number of jumps decreased by 80% directly after surgery. Fifteen days after surgery, the number of jumps normalised, which paralleled an increase in body weight after a 15-day period of body weight decline. By day 31, body weight had normalised to baseline level. Conclusions The data from our study show that the surgery led to decreased motor activity, disturbed health status and loss of body weight in the common marmoset. Full recovery, as assessed by reaching all preoperation values, was reached 31 days after surgery. These data are important to optimise the design of future studies utilising these implantable transmitters.