Agonist-induced stimulation of inositol phosphates in primary rabbit retinal cultures

Carbachol, noradrenaline, and serotonin stimulated the accumulation of inositol phosphates in a dose-dependent manner and maximally by 172.4%, 71.2%, and 51.6%, respectively, in 3-day-old rabbit retinal cultures. In contrast, dopamine, nicotine, isoproterenol, clonidine, 8-OH-dipropylaminotetralin, and gamma-aminobutyric acid were ineffective. In older cultures identified as containing primarily Müller cells, only carbachol and noradrenaline were able to induce a significant stimulatory response. The carbachol-, noradrenaline-, and serotonin-induced responses were pharmacologically characterized and shown to be mediated by muscarinic, alpha 1-adrenergic, and 5-hydroxytryptamine2 receptors, respectively. The results of the present study show that primary retinal cultures of 3 days of age give results comparable with those of the intact retina. Furthermore, it is demonstrated for the first time that putative Müller cells in cultures possess functional muscarinic and alpha 1-adrenergic receptors.