Reflex control of rat tail sympathetic nerve activity by abdominal temperature - PubMed (original) (raw)

. 2014 Jun 24;1(1):37-41.

doi: 10.4161/temp.29597. eCollection 2014 Apr-Jun.

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Reflex control of rat tail sympathetic nerve activity by abdominal temperature

Anthony D Shafton et al. Temperature (Austin). 2014.

Abstract

The thermoregulatory reflex effects of warming and cooling in the abdomen were investigated in 4 urethane-anesthetized Sprague-Dawley rats. Animals were shaved and surrounded by a water-perfused silastic jacket. Skin temperature under the jacket was recorded by thermocouples at 3 sites and brain temperature was monitored by a thermocouple inserted lateral to the hypothalamus. A heat exchanger made from an array of silicon tubes in parallel loops was placed through a ventral incision into the abdomen; it rested against the intestinal serosa and the temperature of this interface was monitored by a thermocouple. Few- or multi-unit postganglionic activity was recorded from sympathetic nerves supplying tail vessels (tail SNA). Intra-abdominal temperature was briefly lowered or raised between 35-41 °C by perfusing the heat exchanger with cold or warm water. Warming the abdomen inhibited tail SNA while cooling it excited tail SNA in all 4 animals. We also confirmed that cooling the trunk skin activated tail SNA. Multivariate analysis of tail SNA with respect to abdominal, brain and trunk skin temperatures revealed that all had highly significant independent inhibitory actions on tail SNA, but in these experiments abdominal temperature had the weakest and brain temperature the strongest effect. We conclude that abdominal temperature has a significant thermoregulatory action in the rat, but its influence on cutaneous vasomotor control appears to be weaker than that of skin or brain temperatures.

Keywords: Thermoregulation; brain; core; reflex; skin.

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Figures

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Figure 1. Chart record from one experiment showing brain, trunk skin and abdominal temperatures along with tail SNA as the raw spike record (bottom) and its 10 s spike count (above). The record spans several episodes of actively warming and cooling in the abdomen, which respectively inhibited and excited tail SNA. At the end of the record the trunk skin was cooled via the water jacket, and the resultant tail SNA was silenced by intravenous hexamethonium (Hex), proving that the activity was postganglionic sympathetic.

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Figure 2. Normalized tail SNA responses to (left to right) abdominal, trunk skin and brain temperatures, calculated by multiple regression analysis of data from the 4 experiments. The respective regression lines are shown with their 95% confidence limits (dashed). All slopes were significantly different from zero (see text).

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