Adrenergic Mechanisms in the Pupillary Light‐Reflex Path

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Abstract
On the basis of the known effects of reserpine on the eye, the presence of monoaminergic mechanisms in the light‐reflex path of the rat was studied with the use of a fluorescence method for the localization of catecholamines and 5‐hydroxytryptamine at the cellular level. The nucleus of Edinger‐Westphal — but not the large‐celled nuclei of the oculomotor complex — was found to receive abundant nerve fibres which show a massive accumulation of a primary cateholamine, in all probability nor‐adrenaline. There is little doubt that the nerves are adrenergic synaptic terminals. This adrenergic system is so richly developed that is must be assumed to play an important role in the regulation of the activity of the visceromotor outflow to the eye. Except this system and the adrenergic neurons recently discovered (Malmfon 1963) in the retina, no other monoaminergic mechanisms have so far been detected with certainty in the light‐reflex path. Abundant fibres of both the adrenergic and 5‐hydroxytryptaminergic type terminate in other parasympathetic (e. g. the dorsal motor nucleus of the vagus) and also sympathetic nuclei (c. g. the sympathetic lateral column of the spinal cord). 5‐hydroxytryptamine and noradrenaline in the central nervous system are thus not confined to action upon the parasympathetic and sympathetic systems respectively. — Current views on the central action of reserpine are discussed on the basis of the findings.