Studies on the sympathetic nervous system: the Valsalva like manoeuvre in sheep

The Valsalva like manoeuvre (VLM) was examined as a test of the responsiveness of the autonomic nervous system in sheep. Within individuals, imipramine pretreatment enhanced the peak blood pressure and heart rate responses to the VLM and atropine prolonged the tachycardia without influencing the peak responses. Between individuals, the peak blood pressure response was related to the degree of hypotension during raised airway pressure (r = 0.77). The degree of hypotension was, in turn, related to gut fill (r = 0.64). Differences in gut fill were ascribed as a cause of variation in the heart rate and blood pressure responses between individual sheep and between the Scottish Blackface and Southdown breeds.