4. THE CIRCULATORY SYSTEM
167
that adrenaline increased the resistance to flow through the systemic
vessels in the eel’s tail.
Tyramine and ephedrine, substances that cause the release of catecholamines from bound sites in mammals, caused a bradycardia and a
transient fall, followed by a rise, in blood pressure in the eel, similar
to that produced by noradrenaline ( Chan, 1967). Cocain, which prevents
the release and reduces the storage of noradrenaline in mammalian
adrenergic nerves, causes a bradycardia and hypertension when injected
into the eel. The bradycardia can be abolished by atropine.
D. Reserpine
This substance depletes the stores and limits the uptake of catecholamines in mammalian tissues. Injections in the eel cause the chromatophores to dilate and the swim bladder to swell, changes consistent with
catecholamine depletion ( Chan, 1967). Reserpine depletes the catecholamine stores in both the lamprey and hagfish heart (Bloom et al., 1961)
and causes a loss in vigor in the hagfish heart which can be restored
by adrenaline (Chapman et al., 1963).
E. Eptatretin
Eptatretin is an unstable amine or amide but, although it has similar
effects, it is not a catecholamine. It has been found only in the hagfish
heart, but has a marked positive chronotropic and inotropic effect on
the heart of many vertebrates, including the hagfish (Jensen, 1963).
F. Histamine
Histamine causes vasoconstriction in the perfused gills of pike and
a fall in blood pressure in the ventral aorta of the eel (see Mott, 1957).
Chan (1967) found that histamine had little or no effect on blood
pressurc in the dorsal and ventral aorta of the eel. Chan used injected
doses of 200 pg, some 100 times greater than that used by Mott.
G. 5-Hydroxytryptamine ( Serotonin)
Chan (1967) found that injections of 25 pg of 5-hydroxytryptamine
caused a slight increase, followed by a decline, in arterial blood pressure
in the eel. N o changes in heart rate or pulse pressure were recorded.
167
that adrenaline increased the resistance to flow through the systemic
vessels in the eel’s tail.
Tyramine and ephedrine, substances that cause the release of catecholamines from bound sites in mammals, caused a bradycardia and a
transient fall, followed by a rise, in blood pressure in the eel, similar
to that produced by noradrenaline ( Chan, 1967). Cocain, which prevents
the release and reduces the storage of noradrenaline in mammalian
adrenergic nerves, causes a bradycardia and hypertension when injected
into the eel. The bradycardia can be abolished by atropine.
D. Reserpine
This substance depletes the stores and limits the uptake of catecholamines in mammalian tissues. Injections in the eel cause the chromatophores to dilate and the swim bladder to swell, changes consistent with
catecholamine depletion ( Chan, 1967). Reserpine depletes the catecholamine stores in both the lamprey and hagfish heart (Bloom et al., 1961)
and causes a loss in vigor in the hagfish heart which can be restored
by adrenaline (Chapman et al., 1963).
E. Eptatretin
Eptatretin is an unstable amine or amide but, although it has similar
effects, it is not a catecholamine. It has been found only in the hagfish
heart, but has a marked positive chronotropic and inotropic effect on
the heart of many vertebrates, including the hagfish (Jensen, 1963).
F. Histamine
Histamine causes vasoconstriction in the perfused gills of pike and
a fall in blood pressure in the ventral aorta of the eel (see Mott, 1957).
Chan (1967) found that histamine had little or no effect on blood
pressurc in the dorsal and ventral aorta of the eel. Chan used injected
doses of 200 pg, some 100 times greater than that used by Mott.
G. 5-Hydroxytryptamine ( Serotonin)
Chan (1967) found that injections of 25 pg of 5-hydroxytryptamine
caused a slight increase, followed by a decline, in arterial blood pressure
in the eel. N o changes in heart rate or pulse pressure were recorded.