title: Neurotransmitter- and neuromodulator-dependent alterations in phosphorylation of protein I in slices of rat facial nucleus.
abstract: Protein I is a neuronal phosphoprotein associated primarily with synaptic vesicles. Regulation of its state of phosphorylation has been investigated in slices of rat facial nucleus. This brainstem motor nucleus has a facilitatory serotonergic input and contains no interneurons. Serotonin (5-hydroxytryptamine, 5-HT, 10(-4) M), in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX, 4 x 10(-5) M), converted approximately 26% of Protein I in these slices from the dephospho-form to the phospho-form. This effect was partially inhibited using two classical 5-HT antagonists, mianserin added to the slices during in vitro incubation and metergoline administered in vivo. The effect of 5-HT appeared to be Ca2+-dependent, unlike that of IBMX (10(-3) M). Adenosine, its analog 2-chloroadenosine, and ATP also increased the phosphorylation of Protein I in facial nucleus slices. 2-Chloroadenosine (5 x 10(-4) M) caused a 29% phosphorylation of Protein I, and this effect was not dependent on extracellular Ca2+. The phosphorylation of Protein I caused both by 2-chloroadenosine and by ATP was inhibited by the adenosine antagonist 2'-deoxyadenosine. Results of additional experiments suggest that the great majority of the Protein I in the facial nucleus is present in presynaptic terminals other than the serotonergic afferents. It is concluded that the stimulation by 5-HT and adenosine of Protein I phosphorylation results largely from a direct action of these compounds on those Protein I-containing terminals.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001933:Brain Stem / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D005154:Facial Nerve / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D016704:Synapsins; D013806:Theophylline / Q000031:analogs & derivatives*
chemical_list: D009419:Nerve Tissue Proteins; D016704:Synapsins; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D013806:Theophylline; D011188:Potassium; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine