Effect of prazosin on the function of the teat sphincter in lactating cows
- 1 May 1984
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Dairy Research
- Vol. 51 (2), 219-226
- https://doi.org/10.1017/s0022029900023475
Abstract
Summary Oxytocin was infused for 60 min into the jugular vein of 8 lactating cows with full udders before milking. Under these circumstances milk loss occurred spontaneously in 3 cows and was evoked in 5 cows by reducing pressure around one teat (–30 cm water) using a plethysmographic chamber. Milk loss was measured continuously. The postsynaptic α-blocking agent prazosin (PRZS) injected either into the udder artery (2 or 5 mg) or into the jugular vein (200 mg) consistently induced a significant increase in milk leakage. It is suggested that PRZS effectively inhibits α-adrenoceptors in the teat sphincter muscles and thus promotes the action of β-adrenoceptors, in this way inducing relaxation of the teat sphincter.Keywords
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