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Raf-1 is a serine/threonine protein kinase that plays a critical role in mitogenic signal transduction. Raf-1 activation requires 14-3-3 binding to Raf-1 as an essential step. This binding is regulated through phosphorylation of Ser259 and Ser621 of Raf-1, each constituting part of the consensus motif for the binding of Raf-1 to 14-3-3. However, Raf-1 kinase kinase(s) that phosphorylates these sites remains unknown. In this report, we detected Raf-1 kinase kinase activity using recombinant glutathione-S-transferase-Raf-1 fusion proteins as substrate of in situ gel kinase assay. Ser259 was phosphorylated by a kinase with a molecular weight of 90 kDa, which was suggested to be Rsk judging from the molecular size, the time course of activation after EGF stimulation and the elution pattern from an anion-exchange column. The Raf-1 fragment containing Ser621 was phosphorylated by kinases with molecular weights of 85, 60, 50 and 48 kDa but not by the kinase that phosphorylates Ser259. These results suggest that although Ser259 and Ser621 lie in the same amino acid sequence motif for 14-3-3 binding, these two regulatory sites for this binding are phosphorylated by different protein kinases.

Methylazoxymethanol (MAM)-induced cerebral hypoplasia resulted in a significant increase in densities of norepinephrine uptake sites in cerebral cortex, suggesting that norepinephrinergic axon terminals were compressed in the smaller brain volumes. The density of beta-adrenergic receptors in MAM-lesioned cerebral cortex was decreased probably due to down-regulation, while there were no changes in the proportions and affinities of agonist high-affinity sites and agonist low-affinity sites in the desensitized beta-receptors.

Methylazoxymethanol (MAM)-induced cerebral hypoplasia resulted in a significant increase in densities of both serotonin uptake sites in frontal cortex and dopamine uptake sites in striatum, suggesting serotonergic and dopaminergic axons terminals were compressed in the smaller brain volumes. The density of S2 serotonin receptors in MAM-lesioned frontal cortex was decreased probably due to down-regulation, while densities of D1 and D2 dopamine receptors in striatum were identical between MAM-lesioned rats and control rats.

Since it has been reported that dopamine D2 receptors are elevated in the brain striatum of spontaneously hypertensive (SH) rats, and since both D1 and D2 receptors may interact with one another, we measured the densities of both these receptors in SH rat striatum, as well as those in the normotensive Wistar-Kyoto rat striatum. The D1 receptor density in both strains was virtually the same, 72.9 +/- 2.2 and 71.3 +/- 3.2 pmol/g, respectively (mean +/- SD). The D2 receptor densities were also almost identical, 16.3 +/- 0.6 and 16.8 +/- 1.0 pmol/g, respectively (mean +/- SD). Thus, these data do not support the concept of a dopamine receptor related role in spontaneous hypertension.