1. The morphology of the smooth muscle of the @entity95 portal vein and its innervation were studied with fluorescence and electron microscopy. Two layers of smooth muscle were observed in the tunica media: an inner layer of circularly arranged muscle cells and an outer layer consisting of bundles of smooth muscle cells arranged in a near longitudinal direction. The membranes of neighbouring smooth muscle cells were occasionally fused to form ;tight junctions'.2. Bundles of non-myelinated nerve fibres were observed in the adventitia, and between bundles and layers of smooth muscle cells in the media. Studies on longitudinal sections with fluorescence microscopy revealed a network of varicose noradrenergic axons.3. Electrical and mechanical activity was recorded from longitudinal strips of smooth muscle from the media of the vein with a @entity969 -gap apparatus.4. The preparation was spontaneously active under minimal resting tension (less than 150 mg) and at temperatures above 28 degrees C. Slow depolarizations led to a burst of spikes (multi-spike complexes), which corresponded to rhythmic contractions. In 10% of preparations, the interval between multi-spike complexes showed a slower depolarization, suggesting the record was from a pace-maker region.5. The frequency of spontaneous activity (3-27 beats/min) was very sensitive to changes in temperature and tension.6. Noradrenaline in low doses (0.01 mug) caused an increase in frequency of the multi-spike complexes. Higher doses (0.1-0.3 mug) initiated continuous high-frequency spiking, while very high doses (0.6-2.0 mug) caused maintained depolarization.7. Responses to repetitive electrical stimulation of the vein were qualitatively similar to those in response to exogenous @entity1063 . The relation between the mechanical response and the various parameters of stimulation was consistent with the stimulation of sympathetic nerve fibres in the wall of the vein.8. The actions of @entity3044 , @entity5521 and @entity1169 indicated the presence of alpha ;excitatory' and beta ;inhibitory' adrenotrophic receptors on the smooth muscle.

Some properties of the smooth muscle of XXXX portal vein.

@entity1169 :: ('MESH:D011433', 'Chemical') :: ['propranolol'] @entity5521 :: ('MESH:D010646', 'Chemical') :: ['phentolamine'] @entity95 :: ('9986', 'Species') :: ['rabbit'] @entity969 :: ('MESH:D013395', 'Chemical') :: ['sucrose'] @entity3044 :: ('MESH:D007545', 'Chemical') :: ['isoprenaline'] @entity1063 :: ('MESH:D009638', 'Chemical') :: ['noradrenaline']
@entity95 :: (9986,Species) :: ['rabbit']
