Diurnal Fluctuations of Heart Rate, Body Temperature and Locomotor Activity in the House Musk Shrew (Suncus murinus).

Abstract

Diurnal fluctuations of heart rate (HR), body temperature (BT) and locomotor activity (LA) in the unanaesthetized and unrestrained house musk shrew (Suncus murinus) were studied using a telemetry system. Six adult male shrews (Jic:SUN) weighing 60-70 g were used in the present study. They were housed under conditions of 24 C and a 12/12-hr light-dark cycle. HR, BT and LA were recorded over 10 days, following the post-implantation period (10 days or more) of the telemetric transmitter. A clear nocturnal rhythm of LA was shown, while intermittent and short-term LA were shown during the light period. The mean HR was 323.5 +/- 8.8 bpm in the light period and 354.3 +/- 5.2 bpm in the dark period, and the fluctuation of HR showed a nocturnal pattern. A nocturnal pattern was also observed in BT fluctuation, and all animals lowered their body temperature from 35-37 C to approximately 30 C or below, mostly during the light period. The fall of body temperature progressed over 2-3 hr, and then rose to the baseline temperature rapidly within approximately 30 min. While the body temperature fell, HR markedly decreased to approximately 100 bpm. These results suggest that the shrew has unique physiological properties in maintaining metabolic balance which are anticipated to be caused by the dramatic alteration of the autonomic nervous function.

Behavioral Patterns Associated with Chemotherapy-Induced Emesis: A Potential Signature for Nausea in Musk Shrews

“…This is not surprising since the chambers were novel for these animals and were likely to promote exploratory behavior. Notably there were small increases in activity during the dark phase (e.g., locomotion and rearing), which has been reported in other studies using musk shrews (Ishii et al, 2002). …”

Insectivores (Hedgehogs, Moles, and Tenrecs)

“…Torpor occurs in shrews, some golden moles, and tenrecs (Reeve 1994). Shrews have some of the highest metabolic rates, oxygen consumption rates, water turnover, and heart and respiration rates of any mammal (Ishii et al 2002;Ochocinska & Taylor 2005). Although moles are adapted to low oxygen environments and can tolerate prolonged hypoxemia, it is no reason to allow this to occur during the perianesthetic period.…”

Changes in Ucp1, D2 (Dio2) and Glut4 (Slc2a4) mRNA Expression in Response to Short-Term Cold Exposure in the House Musk Shrew (Suncus murinus)

“…Environmental conditions were 10-12°C, 30-60% humidity, and a 12L:12D light cycle (photoperiod: 08:00-20:00), with free access to water and commercial trout pellets (Nippon Formula Feed Manufacturing Co., Ltd.). All exposure experiments were timed to end between 18:00 and 20:00 to avoid the effects of daily torpor, during which body temperature decreases for several hours per day; torpor in this species is principally observed in the morning [12]. We euthanized suncus using cardiac exsanguination under ether anesthesia, measured blood sugar levels with a Medisafe Reader GR-101 (Terumo Co., Ltd., Tokyo, Japan), and collected the soleus, heart, and IBAT immediately.…”