title: Disruption of iris adrenergic transmission as an index of poor endorphin modulation in headache.
abstract: Pupillometry was used to evaluate the effect of oral or topically applied adrenomimetic drugs and of local morphine on pupillary size in headache patients and controls. In headache sufferers, a disruption of adrenergic transmission is suggested since the iris adrenergic nerve terminal is apparently poor in NE; this neuron also exhibits a reduced capacity of neurotransmitter synthesis and an adrenoceptor hypersensitivity. The spontaneous reduction of pupillary size detected in headache sufferers also suggests a decreased sympathetic input. The miosis, registered after conjunctival instillation of morphine, demonstrates that iris is a possible example of an opioid-dependent adrenergic neuron in man. A poor modulation of the iris adrenergic transmission induces, in headache sufferers, a neuronal incontinence and therefore a chronic intrasynaptic leakage of NE, resulting in an exhausted empty neuron on the one hand and a compensatory hyperactivity of the effector muscular cell on the other. Since indirect evidence suggests a morphine modulation of the iris adrenergic neuron, a deficiency of endorphin modulation could be the mechanism of disruption of iris adrenergic transmission. Apart from the theoretical aspects, the exploration of iris neuroeffector junction represents a noninvasive an simple diagnostic tool in headache.
mesh_terms: D004723:Endorphins / Q000502:physiology*; D005277:Fenfluramine; D006145:Guanethidine; D006261:Headache / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007498:Iris / Q000187:drug effects*; D009451:Neuroeffector Junction / Q000502:physiology; D010656:Phenylephrine; D011812:Quinuclidines; D011941:Receptors, Adrenergic / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects; D012025:Reflex, Pupillary; D013566:Sympathomimetics; D009435:Synaptic Transmission; D014439:Tyramine
chemical_list: D004723:Endorphins; D011812:Quinuclidines; D011941:Receptors, Adrenergic; D011957:Receptors, Opioid; D013566:Sympathomimetics; D010656:Phenylephrine; D005277:Fenfluramine; D014439:Tyramine; D006145:Guanethidine