The HD‐XG glucose telemetry implant from DSI provides the ability to obtain continuous, real‐time, blood glucose measurements in rodents. The goal of the current study was to compare spot blood glucose measurements with values obtained using telemetry in male and female DSS. Male and female rats were implanted with glucose telemeters at 11 weeks of age, and allowed 1 week to recover before being placed on receivers. Rats were maintained on a normal‐salt, normal‐fat (NF; 16% caloric intake from fat) diet for 1 week and then were switched to a high‐fat diet (HF; 65% caloric intake from fat) for 4 weeks (n=4–5/group sex). Additional rats without telemeter implants were maintained on normal‐salt, normal‐fat diet for the duration of the experiment. All rats gained weight over the 4 week treatment period, however, rats of both sexes on a HF diet exhibited a significantly greater increase in body weight compared to rats on NF (males: 15±1% on NF vs. 22±2% on HF, p<0.05; females: 12±1% on NF vs. 18±2% on HF, p<0.05). There was not a sex difference in weight gain in response to HF diet. Mean absolute relative differences in blood glucose as measured by the HD‐XG compared to spot glucose ranged from 0.1% up to 4.8% in males and 0.7% up to 8.9% in females, indicating that the 2 measurements were always within 10% of one another. Baseline blood glucose levels in male and female DSS measured by HD‐XG were comparable (109±2 vs. 111±2 mg/dL, respectively). HF diet for 4 weeks did not significantly alter blood glucose levels in either sex (male: 106±3 mg/dL; female: 104±4 mg/dL). Additionally, average weekly glucose for both sexes were statistically identical whether analyzed over 24 hour periods or limited to only the light or dark periods. From this study we can conclude the following: 1) glucose telemeters are a reliable methods to obtain continuous measurements of blood glucose in male and female rats, 2) there are no sex differences in blood glucose following a 4 week HF diet in DSS, and 3) DSS are able to tolerate a HF diet with minimal alterations in body weight or blood glucose.

New technology was employed in a novel way to monitor the effect of diet change on continuous blood glucose in addition to standard hemodynamic parameters. A new telemetry implant (HD‐S11‐F2, DSI) enables researchers to collect and transmit data at a different radio‐frequency (18MHz) than the traditional 455KHz implants. While a second frequency allows for social housing and tighter density of research subjects, in this experiment the 18MHz device was paired with a continuous glucose telemetry implant (HD‐XG, DSI) in the same animal. Implantation of two devices in a single animal allowed us to measure blood pressure, ECG, arterial blood glucose, body temperature and activity in a single rat. Six male Sprague Dawley rats were implanted with 2 telemetry implants that each required an arterial site for sensor placement. The HD‐XG sensor was placed in the descending abdominal aorta and the device body was located IP. The HD‐S11‐F2 was inserted in the femoral artery and the catheter tip was advanced to the abdominal aorta (just cranial to the iliac bifurcation), not overlapping the glucose sensor. The HD‐S11‐F2 implant body was placed subcutaneously on the flank. After recovery from surgery, animals were enrolled in a cross‐over designed study to compare the physiologic effects of offering high carbohydrate or low carbohydrate treats after a 12 hour fast. Blood pressure, heart rate and blood glucose values are presented. Marshmallows and mangos were offered as high carbohydrate treats while cheese cubes were offered as the low carbohydrate treat. Approximately 1 hour after the treat offering, the standard rat chow was restored to the cage feeders. The excitement from the technician opening the cage was evident in HR and BP changes associated with that activity. Blood glucose levels from 9–12 hours post‐fast were approximately 92 mg/dl in both groups. Eating marshmallows and mango caused a rapid rise to ~103 mg/dl in ~30 minutes. Eating cheese resulted in a modest rise in blood glucose (~96 mg/dl). These experiments demonstrate a successful surgical approach using two implants to get a more comprehensive picture of whole animal cardiovascular and metabolic physiology.

Continuous data recording, using telemetry, is the preferred way of collecting electrocardiographic (ECG) data in conscious freely moving animals. In small animals, however; the resulting recordings can have indistinguishable P, Q, R, S and T segments due to low signal to noise ratios. In large animals, this has been addressed using wireless telemetry devices with an intravascular negative electrode, or solid tip lead (STL). The purpose of this study was to determine if STLs could be implanted in rats and result in improved ECG signal quality and sensitivity to detect changes when compared to subcutaneous (SQ) leads. Three groups of Sprague Dawley rats (SQ lead placement, STL with shallow placement in the jugular vein, STLs with deep placement in the cranial vena cava) were dosed with verapamil to induce predictable interval changes in the ECG. The three types of ECG signals were compared for ease of automated analysis and signal quality through Q, R, S and T match and noise parameters. STLs resulted in improved signal quality and increased PR interval change following dose. Average number of waveform complexes identified as “bad” by the analysis software was substantially lower in the STL placements than the data collected with SQ electrodes. STLs were successfully implanted in rats and necropsy showed variable tip locations with no gross abnormalities. This application could be especially useful in other small animal models such as the guinea pig, to increase ECG quality and improve automated ECG analysis.

Continuous data recording, using telemetry systems, has proven to be the preferred way of collecting electrocardiogram (ECG) data in conscious freely moving animals. In small animals, however; the resulting recordings can have indistinguishable P, Q, R, S and T segments due to low signal to noise ratios. In large animals, similar challenges have been addressed by equipping wireless telemetry devices with an intravascular negative electrode, or solid tip lead (STL). The purpose of this study was to determine if STLs could be implanted in rats and result in improved ECG signal quality when compared to conventional subcutaneous leads. Two groups of Sprague Dawley rats, one with conventional lead placement (subcutaneous) and the other using the STL (vascular) were surgically implanted. ECG data were collected multiple times over a one year period. Signal quality was qualitatively and quantitatively evaluated between the STL and conventional lead groups, using a side by side visual comparison, and automated Q, R, S and T match percentage, by an experienced ECG analyst. ECG data collected with a STL was observably clearer when compared to the conventional lead group. At the completion of the study, the rats implanted with STLs were subjected to thorough necropsies. A histological examination of the tissue surrounding the STL was completed. In conclusion, STLs were successfully implanted in rats, resulting in improved signal quality with no detrimental evidence of inflammation noted at necropsy. The two ECG signals were compared for ease of automated analysis through comparison of Q, R, S and T match. This application could be especially useful in other small animal models such as the ferret or guinea pig, to increase ECG quality and improve automated ECG analysis.