Sympathetic nervous control of adrenaline release from the head kidney of the cod, gadus morhua

Abstract

1. The release of catecholamines from the chromaffin tissue by different kinds of stimulation has been studied in the perfused head kidney of the cod, and in intact and operated fish in vivo. 2. Fluorimetric analysis of the perfusate shows a dose-dependent release of adrenaline and noradrenaline by acetylcholine in the dose-range 10 −9−10 −7 mol. Similarly, both acetylcholine and nicotine produce an increased outflow of label from the head kidney pre-loaded with 3H-adrenaline. 3. Electrical stimulation of the nervous supply to the left cardinal vein produces release of endogenous catecholamines. In head kidneys pre-loaded with 3H-adrenaline, an increase in the outflow of label is elicited by electrical stimulation with an optimal frequency of 20 Hz for a 30 sec stimulation period. 4. The release of label from the head kidney pre-loaded with 3H-adrenaline produced by either acetylcholine or electrical stimulation is inhibited by hexamethonium (3 × 10 −5−10 −4 M). 5. Stress, induced by keeping the fish in air for 15 min, increases the plasma levels of adrenaline and noradrenaline >4-fold. This effect is prevented by bilateral sectioning of the 1st to 4th spinal nerves with their preganglionic sympathetic outflow. 6. It is concluded that the chromaffin tissue of the cod head kidney is under sympathetic nervous control by medullated fibres which are probably preganglionic and cholinergic.