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Neurogenic and Myogenic Responses in Isolated Smooth Muscle of The Bovine Teat
Neurogent och myogent betingade reaktioner i den glatta muskulaturen i preparationer från spenar hos kor.
Acta Veterinaria Scandinavica volume 25, pages 385–402 (1984)
Abstract
Strips of bovine teat smooth muscle were studied. Their innervation was investigated with analytical pharmacology on field stimulated preparations. The content of noradrenaline in the teat wall and the sphincter region was determined. The main results were: teat smooth muscle has properties of single unit smooth muscle i.e. automaticity and active response to stretch. Especially the sphincter region is inclined to rapid phasic rhythmicity. The teat smooth muscle receives excitatory adrenergic innervation. The noradrenaline released from the nerves preferentially activates α-adrenoceptors, while β-adrenoceptors essentially are noninnervated and humoral. The sphincter region has a higher concentration of noradrenaline and a more intimate neuro-effector arrangement. This is probably of functional significance. Moderate chilling increases the response to adrenergic nerve stimulation while it is decreased at higher temperatures. This has most likely physiological importance. The results are discussed with respect to in vivo findings and it is concluded that the bovine teat smooth muscle with its excitatory adrenergic nerves forms a normally very efficient neuro-effector system with a particular strength in the sphincter around the streak canal.
Sammanfattning
Preparationer (strips) av den glatta muskulaturen i kospenar har studerats. Innervationen har undersökts genom analytisk farmakologi på fältstimulerade preparationer. Innehållet av noradrenalin i spenväggen och spenkanalsfinktern har bestämts. De huvudsakliga resultaten är följande. Spenens glatta muskulatur reagerar som „singleunit“ muskulatur, d. v. s. den är spontanaktiv och svarar på sträckning med kontraktion. Särskilt sfinktern har förmäga till snabb fasisk rytmicitet. Spenmuskulaturen har excitatorisk adrenerg innervation. Noradrenalin från nervändarna aktiverar i första hand α-adrenoceptorerna under det att β-adrenoceptorer främst aktiveras humoralt. Sfinktern har högre koncentration av noradrenalin än annan spenmuskulatur och också effektivare neuromuskulär överledningsmekanismer, vilket sannolikt har funktionell betydelse. Mättlig avkylning ger förstärkt svar på adrenerg nervstimulering, medan uppvärmning till högre temperaturer (mer an 40 °C) ger motsatt effekt. Även detta har sannolikt funktionell betydelse. Normalt utgör sålunda den glatta spenmuskulaturen hos ko med dess excitatoriska adrenerga innervation ett effektivt neuro-effector system. Särskilt gäller detta spenkanalsfinktern. Resultaten diskuteras mot bakgrund av spenmuskelreaktioner in vivo.
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Isaksson, A., Sjöstrand, N.O. Neurogenic and Myogenic Responses in Isolated Smooth Muscle of The Bovine Teat. Acta Vet Scand 25, 385–402 (1984). https://doi.org/10.1186/BF03547253
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DOI: https://doi.org/10.1186/BF03547253