Involvement of peptide histidine isoleucine (PHI) in prolactin secretion induced by serotonin in rats

Dopamine and the phosphorylated dopamine transporter are increased in the diacylglycerol kinase η-knockout mouse brain

The molecular mechanisms generating the mania-like abnormal behaviors caused by diacylglycerol (DG) kinase (DGK) η deficiency remain unclear. Here, we found that DGKη knockout markedly increased dopamine (DA) levels in the midbrain (DA-producing region, 2.8-fold) and cerebral cortex (DA projection region, 1.2-fold). Moreover, DGKη deficiency significantly augmented phosphorylated DA transporter (DAT) levels (1.4-fold increase), which induce DA efflux to the synaptic cleft, in the cerebral cortex. Moreover, phosphorylation levels of protein kinase C-β, which is activated by DG and involved in DAT phosphorylation, were also increased. DAT expressed in Neuro-2a cells recruited DGKη to the plasma membrane and colocalized with it. These results strongly suggest that dopaminergic hyperfunction caused by DGKη deficiency in the brain leads to mania-like behaviors.

Stimulation by serotonin of immunoreactive peptide histidine isoleucine release from rat hypothalamus in vitro

The effect of serotonin (5-HT) on the release of peptide histidine isoleucine-like immunoreactivity (PHI-LI) from rat hypothalamus was investigated in vitro with a perifusion system. A high potassium concentration (56 mM) stimulated PHI-LI release in a calcium-dependent manner. PHI-LI release was dose-relatedly stimulated by 5-HT (10(-6), 10(-5) and 10(-4) M). PHI-LI release induced by 5-HT (10(-5) M) was abolished by cyproheptadine (10(-4) M), a 5-HT antagonist. These results suggest that 5-HT has a stimulating effect on PHI release from the hypothalamus.