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Developmental Changes of Cerebral Cortical [ 3 H]Clonidine Binding in Rats: Influences of Guanine Nucleotide and Cations
Author(s) -
Nomura Yasuyuki,
Kawai Masanori,
Mita Kayoko,
Segawa Tomio
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb02778.x
Subject(s) - binding site , gtp' , guanine , receptor , chemistry , nucleotide , biology , biochemistry , stereochemistry , biophysics , enzyme , gene
Cerebral cortical [ 3 H]clonidine binding and influences of GTP and cations were investigated in developing rats. The results from Scatchard plots were compatible with the presence of two populations of binding sites [high‐affinity binding ( K D = 0.59 n M ) and low‐affinity binding ( K D = 7.12 n M )] in 70‐day‐old rats but only high‐affinity binding ( K D = 0.27 n M ) on day 1. Low‐affinity binding was detectable on day 7. K D values in high‐ and low‐affinity binding were not significantly changed during development after 7 days. B max of high‐affinity binding reached a peak on day 15, and the value of low‐affinity binding gradually increased with age. The addition of 10 μ M GTP caused a significant reduction in B max of high‐affinity binding after day 7. Neither K D nor B max of low‐affinity binding was affected by 10 μ M GTP during development. NaCl (10 and 100 m M ) diminished the binding on days 7 and 70. MnCl 2 (0.1 and 1.0 m M ) markedly increased the binding on days 15 and 70 but not on day 7. It is suggested that: (1) single binding sites of α 2 ‐adrenoceptors with higher affinity seem to be present on day 1; (2) low‐affinity binding appears on day 7; (3) the number of high‐affinity binding sites reaches a peak on day 15, followed by changes in populations of high‐affinity as well as low‐affinity sites without changing affinity; (4) the regulatory mechanism in α 2 ‐receptors by guanine nucleotide reaches functional maturity between days 1 and 7; and (5) the involvement of Na + and Mn 2+ in α 2 ‐receptor binding becomes functional by days 7 and 15, respectively.