An Analysis of the Responses of the Isolated Portal Vein of the Rabbit to Electrical Stimulation and to Drugs

Abstract

Transmural electrical stimulation has been used to investigate responses of isolated intestinal smooth muscle preparations to nerve stimulation (Paton, 1955;Day & Vane, 1963;Paton & Vane, 1963;Birmingham & Wilson, 1965;Burnstock, Campbell & Rand, 1966). Paterson (1965) stimulated isolated arterial strips transmurally and showed that the ensuing contractions were probably caused by excitation of post-ganglionic adrenergic neurones in the vessel wall.Isolated venous muscle reacts to drugs (Franklin, 1925;Sutter, 1965) but little is known about its response to electrical excitation. We have, therefore, investigated the effects of transmural stimulation on the portal vein of the rabbit; the results show that this tissue has an innervation which can cause both excitatory and inhibitory effects. In addition, there is a non-adrenergic non-cholinergic inhibitory innervation. METHODSMale albino rabbits weighing 2-3 kg were killed by breaking the neck. The abdomen was opened and the portal vein was exposed and cleared of surrounding tissue. The length of portal vein, starting at the junction of the splenic and the superior mesenteric veins and ending at its bifurcation into right and left branches, was cut out and washed in cold Krebs solution. The vein was opened along its longitudinal axis to form a flat strip of tissue 3-4 cm long. Threads were attached to each end, and the strip was suspended vertically in a 50 ml. organ bath containing Krebs solution at 37' C, gassed with 95% oxygen and 5% carbon dioxide. The lower end of the strip was tied to a glass rod, while the upper end was attached to an isometric transducer (tensile sensor, Type S.T.I. Ether-Langham Thompson Ltd.). The transducer formed part of a bridge circuit, the output of which was recorded on a potentiometric millivolt recorder (Texas Instruments ServoRiter) through suitable attenuation. To stimulate the isolated vein, two pairs of parallel platinum wires, 3 cm long, were mounted longitudinally on opposite internal faces of a Perspex cylinder 4 cm long and 1 cm internal diameter. The cylinder was fixed in the organ-bath and the vein was suspended within it. Thus the electrodes lay parallel to the vein on each side of it but not touching it. For transmural stimulation, two stimulators with identical outputs were connected in parallel, in order to give sufficient power output to ensure maximal excitation.The vein was stimulated with rectangular pulses of 0.5-1 msec duration and full voltage output from the stimulators (80 V). Stimulus frequencies varying from 15/min to 50/sec were used. It was

The effect of isoprenaline on adrenoceptors in human saphenous vein

“…Sutter (1965) found that the external jugular vein of the rabbit was not contracted by isoprenaline but that low doses (below 10 ,ug/ml) caused relaxation of the anterior mesenteric vein (isoprenaline caused contraction above 10 ug/ ml). Hughes & Vane (1967) have shown that isoprenaline (10 ng/ml-1 jg/ml) relaxes the rabbit isolated portal vein, but Hughes (1967) could not demonstrate that isoprenaline in doses up to 10 jg/ml contracted human isolated saphenous vein.…”

A comparison of the excitatory and inhibitory effects of non‐adrenergic, non‐cholinergic nerve stimulation and exogenously applied ATP on a variety of smooth muscle preparations from different vertebrate species

“…Some of these are excitatory, as for example those to the urinary bladder (Henderson & Roepke, 1934;Chesher, 1967;Dumsday, 1971;Burnstock, Dumsday & Smythe, 1972) and to segments of the gut in lower vertebrates (Everett, 1968;Carter, 1969;Bartlet & Hassan, 1971; Sneddon, Smythe, Satchell & Burnstock, to be published). Others are inhibitory, for example those to the amphibian and reptile lung (Wood & Burnstock, 1967;Campbell, 1971;Robinson, McLean & Burnstock, 1971;Berger, 1972;Schnizer, Hoang & Brecht, 1968) and parts of the vascular system (Hughes & Vane, 1967, 1970. It is not yet known whether any, some, or all of these nerves are purinergic or whether they release yet further neurotransmitters, although some evidence has been presented that those supplying the toad lung (Robinson et al, 1971), guinea-pig bladder (Dumsday, 1971;Burnstock et al, 1972), toad intestine (Sneddon et al, 1972) and rabbit portal vein (Hughes & Vane, 1967) may release ATP.…”

“…Others are inhibitory, for example those to the amphibian and reptile lung (Wood & Burnstock, 1967;Campbell, 1971;Robinson, McLean & Burnstock, 1971;Berger, 1972;Schnizer, Hoang & Brecht, 1968) and parts of the vascular system (Hughes & Vane, 1967, 1970. It is not yet known whether any, some, or all of these nerves are purinergic or whether they release yet further neurotransmitters, although some evidence has been presented that those supplying the toad lung (Robinson et al, 1971), guinea-pig bladder (Dumsday, 1971;Burnstock et al, 1972), toad intestine (Sneddon et al, 1972) and rabbit portal vein (Hughes & Vane, 1967) may release ATP.…”

Mediation by the same muscarinic receptor subtype of phasic and tonic contractile activities in the rat isolated portal vein

“…In most vessels the net effect is a pronounced vasodilatation, although there are exceptions, for instance, the mesenteric portal vein of several species (Hughes & Vane, 1967;Uematsu et al, 1984). The contraction implies the existence of muscarinic receptors on the smooth muscle cells which subserve an excitatory function.…”