Dec 1, 1977

Analysis of the beta-receptor mediated effect on fast-contracting skeletal muscle in vitro

Naunyn-Schmiedeberg's Archives of Pharmacology
E Holmberg, B Waldeck

Abstract

Subtetanic contractions of the isolated extensor digitorum longus (EDL) of the guinea-pig, a fast-contracting muscle, were evoked by transmural field stimulation. Isoprenaline, adrenaline, terbutaline, and noradrenaline each caused a dose-dependent increase in the force of contraction, their potencies decreasing in that order. Tyramine was without effect in this respect. Curare depressed the contractions of EDL by about 20% but did not appreciably change the response to the beta-adrenoceptor agonists. The effects of isoprenaline and noradrenaline were blocked by propranolol (unselective) and H 35/25 (1-(p-tolyl)-2-isopropylamino-1-propanol, beta2-selective) but not by practolol (beta1-selective). Moreover, the increase in the force of subtetanic contractions of EDL produced by noradrenaline was unaffected by phentolamine. It is concluded that the adrenoceptor mediating the increase in the force of contraction of the isolated EDL is of the beta2-type and that the site of action is direct on the muscle. Its similarity to the receptor mediating the inverse effect on the slow-contracting soleus-muscle is pointed out.

Mentioned in this Paper

Practolol
Depressed - Symptom
Cavia
Contraction (Finding)
Soleus Muscle Structure
Norepinephrine, (+, -)-Isomer
Terbutalin von ct
Tyramine
Epinephrine Measurement
Adrenergic Receptor

About this Paper

Related Feeds

Adrenergic Receptors: Trafficking

Adrenergic receptor trafficking is an active physiological process where adrenergic receptors are relocated from one region of the cell to another or from one type of cell to another. Discover the latest research on adrenergic receptor trafficking here.