3H-thymidine long survival autoradiography as a method for dating the time of neuronal origin in the chick embryo: The locus coeruleus and cerebellar Purkinje cells

Authors

  • Lorraine Yurkewicz,

    1. Laboratory of Neuropsychopharmacology, Department of Biobehavioral Sciences University of Connecticut, Storrs, Connecticut 06268
    Current affiliation:
    1. Department of Anatomy and Neurobiology, Washington University, School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110
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  • Jean M. Lauder,

    1. Laboratory of Developmental Neurobiology, Department of Anatomy, University of North Carolina, School of Medicine, Chapel Hill, North Carolina 27514
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  • Mario Marchi,

    1. Laboratory of Neuropsychopharmacology, Department of Biobehavioral Sciences University of Connecticut, Storrs, Connecticut 06268
    Current affiliation:
    1. Institute of Pharmacology and Pharmacognosy, University of Genova, 16146, Genova, Italy
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  • Ezio Giacobini

    1. Laboratory of Neuropsychopharmacology, Department of Biobehavioral Sciences University of Connecticut, Storrs, Connecticut 06268
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Abstract

Contrary to previous assumptions, we have found that a single dose of 3H-thymidine (25 μCi), injected into the yolk sac of White Leghorn chick eggs on 2 days of incubation (d.i.) only remains available for DNA-synthesizing (proliferating) cells for 48 hours following the time of injection. This finding now makes it possible to date the time of neuronal origin in the avian embryo using a single injection of isotope and a long survival time (30 days posthatch) as in mammalian studies where 3H-thymidine is only available as a short “pulse.” Using this method, we have determined that neurons in the chick locus coeruleus (LC) cease proliferation on 2–6 d.i. with a peak of neuronal genesis on 3–5 d.i. In addition, neuronal genesis is not homogeneous throughout the LC cell population, but occurs in a predominantly caudorostral gradient. Conversely, the cerebellar Purkinje cells cease division on 3–8 d.i. with a peak of heavy labeling on 4–6 d.i., 1 day later than that observed in the LC.

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