Effects of ceruletide on perioral movements and the dopamine receptor-adenylate cyclase system in rats chronically treated with fluphenazine

Low baseline serotonin-2A receptors predict clinical response to olanzapine in first-episode schizophrenia patients

The purpose of this study was to determine whether platelet serotonin-2A (5-HT2A) binding sites and inositol 1,4,5 trisphosphate (IP3) concentrations before treatment can identify olanzapine-responsive patients. The study included 21 never medicated, first-episode schizophrenia patients (antipsychotic-naïve) and 21 patients with a DSM-IV-TR diagnosis of paranoid schizophrenia who had not received depot antipsychotic treatment in the previous 6 months or oral antipsychotic or antidepressant treatment in the previous 2 months (antipsychotic-free). In the antipsychotic-naïve group, olanzapine responders had a significantly lower number of 5-HT2A receptors and lower IP3 concentrations at baseline than non-responders. The combination of baseline 5-HT2A and IP3 values significantly predicted an improvement in negative symptomatology after 6 weeks of treatment with olanzapine. In the antipsychotic-free group, responders had significantly higher positive and lower negative symptomatology at baseline, together with a reduced number of 5-HT2A receptors. However, basal 5-HT2A receptors or IP3 concentrations did not significantly predict positive, negative or general clinical response. The reported results suggest that platelet 5-HT2A binding might be a trait marker that could help to identify those patients likely to show greater improvement in negative symptomatology after olanzapine treatment.

Decrease of adenylyl cyclase activity and expression by a sigma1 receptor ligand and putative atypical antipsychotic

We examined whether changes in the adenylyl cyclase system could be induced by the administration of the sigma1 receptor ligand and putative atypical antipsychotic 4-[4-fluorophenyl]-1,2,3,6-tetrahydro-1-[4-[1,-2,4-triazol-1-il]butyl]pyridine citrate) (E-5842). Repeated (21 days) but not acute (2 h) treatment with E-5842 induced a significant decrease in adenylyl cyclase type I immunoreactivity and adenylyl cyclase activity in rat frontal cortex membranes, with less or no effect in other brain regions such as the hippocampus or the striatum. Changes in immunoreactivity were not observed in other adenylyl cyclases (type V/VI). The reported changes, observed only after a chronic treatment, could be related to the mechanism of action of sigma receptor ligands in general or to that of E-5842 in particular and should be taken into account, given the long duration of treatment in psychiatric patients.

The effect of a cholecystokinin agonist on masseter muscle activity in the cat

The CCK(B) agonist, pentagastrin, has been shown to induce anxiety in human subjects. Similarly, in the cat model, pentagastrin facilitates the expression of hypothalamically activated emotional behavior. Because hypothalamically mediated emotional behavior is also accompanied by increased EMG activity in the jaw muscles, these experiments were designed to examine the combined effects of administration of pentagastrin with activation of hypothalamically mediated emotional behavior upon jaw muscle EMG activity. Electrodes were carefully lowered through previously placed guide tubes overlying the hypothalamus until a behavioral site was identified. Following the establishment of a stable threshold current for eliciting an emotional behavioral response, the skin overlying the ipsilateral masseter muscle was shaved and cleaned with alcohol, and surface electrodes were attached. The EMG was recorded, amplified, digitized, and stored in a microcomputer for analysis. Mean power frequencies (MPF) and latencies for behavior were calculated for baseline prior to infusion of all drugs. Following this, the effects of intravenous administration of pentagastrin and the CCK(B) antagonist LY288513 on the MPF were determined. The infusion of the CCK(B) agonist, pentagastrin (0.77, 1.92, and 3.84 microg/kg), decreased MPF in a time-related manner. The effects of pentagastrin 1.92 microg/kg were blocked by the CCK(B) antagonist, LY288513 (6.54 microg/kg). In addition, the infusion of LY288513 alone increased MPF. These results are surprising in that pentagastrin's anxiogenic properties would appear to make it likely to facilitate motor activity, not suppress it.

Differential effects of treatment with typical and atypical antipsychotic drugs on adenylyl cyclase and G proteins

We examined the effects of chronic in vivo antipsychotic drug treatments on G protein function and regulation. Mice were treated with typical antipsychotic haloperidol (6 mg/kg per day) and atypical agent olanzapine (20 mg/kg per day) for 14 days via mini-osmotic pumps. G protein-activated adenylyl cyclase activity in brain tissues was measured in the presence of guanine nucleotide analogue guanosine-5'-O(3-thiotriphosphate) tetralithium salt, or GTPgammaS. In frontal cortex, haloperidol treatment produced 21% increases in the GTPgammaS -mediated adenylyl cyclase Emax value (vs. vehicle controls) while olanzapine produced 20% reductions in this value (vs. controls); these effects were significant. In striatum, olanzapine treatment produced significant 31 and 27% decreases in Emax values compared with vehicle and haloperidol treatment, respectively. Chronic haloperidol treatment produced significant 24% reductions in the immunoreactivity of cortical, but not striatal, Gialpha1,2 subunits. There were no effects of chronic olanzapine treatment on G(i)alpha1,2 levels and no effects of either antipsychotic on G(s)alpha, levels. Chronic haloperidol and olanzapine treatments differentially regulate G protein-mediated adenylyl cyclase responses in brain regions possibly relating to their unique effects on G protein-coupled receptors.