Neurotensin-sensitive protein phosphorylation in the rodent caudate nucleus.

1. Caudate nucleus slices from rat brain were prepared and incubated with 5 microM neurotensin for 30 seconds and 5 minutes. Following homogenization of the caudate nucleus slices, proteins were phosphorylated in vitro in the presence of CaCl2 or cyclic AMP. Phosphorylated proteins were separated by electrophoresis, and phosphate incorporation into individual proteins quantitated by microdensitometry of the resultant autoradiographs. 2. Incubation of caudate nucleus slices with neurotensin altered the subsequent in vitro calcium-dependent phosphorylation of several specific protein substrates, but in contrast, incubation with neurotensin altered the subsequent cyclic AMP-dependent phosphorylation of only 1 minor phosphoprotein substrate. 3. These results are consistent with other evidence which implicates calcium as an important intracellular mediator of the neurotensin signal.