Effects of NaCl and sultopride on striatal [3H]spiperone binding in neonatal,adult and senescent rats

Effects of NaCl, (+)-and (?)-sultopride on striatal [³H]spiperone binding was investigated in 7-day, 70-day and 2-year-old rats. The amount of specific [³H]spiperone binding was the highest at 70 days and the value at adult stage was significantly (P < 0.001) higher than those at 7 days and 2 years. NaCl (100 mM) significantly increased [³H]spiperone binding in neonatal (P < 0.01), adult (P < 0.05) and senescent (P < 0.05) animals. Scatchard analysis showed that the Bmax of low-affinity [³H]spiperone binding was significantly elevated by 100 mM NaCl compared to the value in control of adult animals. More potent inhibition of (?)-sultopride for [³H]spiperone binding than that of the (+)-enantiomer at adult stage was also observed at neonatal and senescent stages. NaCl (100 mM) significantly enhanced inhibitory activities of (+)- and (?)-sultopride at every stage. It is suggested that stabilizing effect of Na⁺ on dopamine (DA) receptor complexes and increasing effect of Na⁺ on binding affinity of benzamide to DA₂ receptors keep functions through development and aging.