Neurotransmitter release by certain neuropeptides in the chicken retina

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Abstract
The ability of certain neuropeptides (glucagon, somatostatin, leu‐enkephalin and neurotensin) to release known neurotransmitters (glycine, GABA, dopamine and 5‐hydroxytryptamine) was tested in the chicken retina. Tritiated neurotransmitters were injected intravitreally in chicken eyes. After excision, the retina was stimulated in vitro with the neuropeptide in micromolar concentrations while monitoring the efflux of radioactivity from the retina. A rise of this efflux represents a stimulus dependent release. Neurotensin released [3H] glycine, [3H]dopamine and [3H]5‐hydroxytryptamine. Leu‐enkephalin released [3H]dopamine and somatostatin released [3H]5‐hydroxytryptamine. Glucagon was without effect. [3H]GABA was not released by any of the neuropeptides.