PURPOSE: Previously, retinopetal axons containing histamine and dopaminergic neurons expressing histamine H(1)-receptor had been localized in mouse retinas using anatomic techniques. The goal of these experiments was to demonstrate that these receptors are functional. METHODS: Dopaminergic cells were acutely isolated from retinas of transgenic mice expressing red fluorescent protein under control of the tyrosine hydroxylase promoter and loaded with the calcium indicator Fura-2. RESULTS: Under control conditions, there were spontaneous oscillations in the levels of free intracellular calcium in dopaminergic cells. These oscillations were abolished in nominally calcium-free extracellular medium and in 1 μM tetrodotoxin, findings suggesting that the oscillations were mediated by calcium entry across the plasma membrane in response to sodium-dependent action potentials. Histamine increased the mean free intracellular calcium in the dopaminergic cells by increasing the frequency and/or amplitude of the calcium oscillations. The effects of histamine were dose-dependent and reached maximum at 5 μM. With this dose, there was a 65% increase in the mean free intracellular calcium concentration. The histamine H(1)-receptor antagonist, pyrilamine, blocked the effects of 5 μM histamine when applied at 50 μM. The selective histamine H(1)-receptor agonists, 2-(3-trifluoromethylphenyl) histamine and methylhistaprodifen significantly increased mean free intracellular calcium when applied at 5 μM. CONCLUSIONS: Histamine released from retinopetal axons in the mouse retina can elevate intracellular calcium levels in the perikarya of dopaminergic cells via the activation of histamine H(1)-receptors.
PURPOSE: Previously, retinopetal axons containing histamine and dopaminergic neurons expressing histamine H(1)-receptor had been localized in mouse retinas using anatomic techniques. The goal of these experiments was to demonstrate that these receptors are functional. METHODS: Dopaminergic cells were acutely isolated from retinas of transgenic mice expressing red fluorescent protein under control of the tyrosine hydroxylase promoter and loaded with the calcium indicator Fura-2. RESULTS: Under control conditions, there were spontaneous oscillations in the levels of free intracellular calcium in dopaminergic cells. These oscillations were abolished in nominally calcium-free extracellular medium and in 1 μM tetrodotoxin, findings suggesting that the oscillations were mediated by calcium entry across the plasma membrane in response to sodium-dependent action potentials. Histamine increased the mean free intracellular calcium in the dopaminergic cells by increasing the frequency and/or amplitude of the calcium oscillations. The effects of histamine were dose-dependent and reached maximum at 5 μM. With this dose, there was a 65% increase in the mean free intracellular calcium concentration. The histamine H(1)-receptor antagonist, pyrilamine, blocked the effects of 5 μM histamine when applied at 50 μM. The selective histamine H(1)-receptor agonists, 2-(3-trifluoromethylphenyl) histamine and methylhistaprodifen significantly increased mean free intracellular calcium when applied at 5 μM. CONCLUSIONS:Histamine released from retinopetal axons in the mouse retina can elevate intracellular calcium levels in the perikarya of dopaminergic cells via the activation of histamine H(1)-receptors.
Authors: M J Gastinger; A J Barber; S A Khin; C S McRill; T W Gardner; D W Marshak Journal: Invest Ophthalmol Vis Sci Date: 2001-10 Impact factor: 4.799
Authors: Ursula Greferath; Kirstan A Vessey; Andrew I Jobling; Samuel A Mills; Bang V Bui; Zheng He; Nupur Nag; Hiroshi Ohtsu; Erica L Fletcher Journal: PLoS One Date: 2014-12-29 Impact factor: 3.240
Authors: Annette E Allen; Riccardo Storchi; Franck P Martial; Rasmus S Petersen; Marcelo A Montemurro; Timothy M Brown; Robert J Lucas Journal: Curr Biol Date: 2014-10-09 Impact factor: 10.834