Measurement of physiological parameters and activity in a Mongolian gerbil during gravidity and lactation with an implanted transmitter.

This communication reports the first use of a transmitter implanted into the abdominal cavity of a small pregnant rodent to simultaneously measure the heart rate, core body temperature and general locomotory activity with no apparent side effects to the animals. Using this method the heart rate of one female Mongolian gerbil (Meriones unguiculatus) decreased from a mean of 303 +/- 6 (SE) (beats per minute) during gravidity to a level of 248 +/- 3 (SE) (beats per minute) during lactation. At the same time, the core body temperature increased from 37.7 +/- 0.05 (SE) degrees C to 38.0 +/- 0.03 (SE) degrees C. During pregnancy the general locomotory activity of this female followed the normal nocturnal pattern for this species (i.e., greater activity during the dark period) but there was an overall reduction in activity to 85% of the nonpregnant state. The level of activity was further reduced during lactation to about 43% of the nonpregnant state. This was largely the result of less activity during the dark period so that activity in the dark period and light period became more or less equivalent.