Effects of an extract of Ginkgo biloba and diverse substances on the phasic and tonic components of the contraction of an isolated rabbit aorta

Abstract

1. 1. The effects of phentolamine, propranolol, D 600, theophylline, papaverine and an extract of Ginkgo biloba were studied with respect to the two phases of the contractile response induced by norepinephrine in an isolated rabbit aorta. 2. 2. Phentolamine (3 × 10 −6 M) inhibits the rapid phase of the contraction of the rabbit aorta brought on by norepinephrine (NE) 10 −5 M more strongly than the tonic phase. Propranolol (10 −6 M) potentiates this rapid phase. 3. 3. D 600 inhibits the slow phase with an EC 50 = to 3.8 × 10 −8 M. 4. 4. Papaverine and theophylline increase the relaxation that follows the rapid phase of contraction. The slow phase is inhibited only by papaverine. 5. 5. The extract of Ginkgo biloba (Gb) at a concentration of 3 mg/ml has the same type of effect as papaverine 3 × 10 −5 M.