Parotid secretion daily patterns and measurement with ultrasonic flow probes in conscious sheep

Five sheep under halothane anesthesia were prepared with bilateral transit time ultrasonic flow probes around the parotid ducts. The ducts were fitted with non-obstructive sampling catheters through their oral ends. After probe encapsulation (8 days), salivary flows were continuously recorded (4-5 days, dual-channel ultrasonic flowmeter). For rumination, eating, resting and drinking periods, respectively, the parotid daily outputs recorded were 1.96 +/- 0.57, 0.97 +/- 0.34, 2.84 +/- 0.41 and < 0.041 and bilateral flow rates were 6.76 +/- 0.70, 5.63 +/- 1.42, 2.50 +/- 0.58 and 1.69 +/- 0.88 ml min-1. An ipsilateral secretory reflex was evident when the sheep changed chewing side during rumination (4.44 +/- 0.96 ml min-1 ipsilateral vs 2.63 +/- 0.90 ml min-1 contralateral flow, P < 0.01). Secretory patterns are described in detail during rest, eating, drinking and rumination periods. The pH of parotid saliva (8.36 +/- 0.14) and the osmolality (273.8 +/- 9.9 mosmol kg-1) were independent of secretory rates. In situ probe calibration showed high accuracy (0-9%). The main advantages of the technique are its accuracy and good tolerance, duct integrity and maintenance of nervous supply, minimal surgery, uninterrupted salivary flow, simultaneous bilateral measurements and precise flow monitoring, permitting detailed observations.