Plasma catecholamine metabolites and treatment response at neuroleptic steady state.

Using either haloperidol or perphenazine in a fixed-dose protocol, plasma free homovanillic acid (HVA) and methoxyhydroxyphenethylglycol (MHPG) were decreased in 37 nonorganic psychotic inpatients at neuroleptic steady state (7-9 days) in comparison with pretreatment values. The data indicate that the magnitude of the decline in HVA and MHPG was associated with treatment response and not with neuroleptic plasma levels.

Characteristics of patients with the highest plasma catecholamine metabolite levels.

The authors measured plasma levels of free homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenyl-glycol (MHPG) in 350 consecutive psychiatric patients. Among the 22 patients with the highest values for both HVA and MHPG, the primary diagnoses were psychotic disorders, eating disorders, and major depression.

Diazepam and haloperidol. Effect on regional brain homovanillic acid levels.

Diazepam lowered homovanillic acid levels in brain regions from untreated and haloperidol-treated rats. However, there was evidence of a biphasic effect in that 2 mg/kg was more effective than 10 mg/kg under several conditions. Diazepam was more effective in restoring regional HVA toward control levels following doses of haloperidol in the low clinical range (0.1 to 0.2 mg/kg) than following higher doses. With respect to maximizing dopamine receptor blockade and minimizing compensatory presynaptic activity in the acute treatment of psychotic conditions, our data provide some support for the use of modest doses of neuroleptics and benzodiazepines.

Effects of calcium channel antagonists on the phosphorylation of major protein kinase C substrates in the rat hippocampus.

K(+)-induced depolarization of rat hippocampal slices resulted in significant increases in the phosphorylation state of myristoylated, alanine-rich C kinase substrate (MARCKS; also known as 87K, pp80) and neuromodulin [also known as growth associated protein 43 (GAP43), B50, F1] as determined by back-phosphorylation using protein kinase C. The effect of organic and inorganic Ca2+ antagonists on the phosphorylation of these major protein kinase C substrates in the rat hippocampus was studied to determine whether Ca2+ influx through L- or N-type voltage-sensitive Ca2+ channels was required for the phosphorylation changes observed. The depolarization-induced changes appeared to be dependent on extracellular Ca2+, based on evidence indicating that the chelation of extracellular Ca2+ with ethylene glycol-bis (beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited these changes. In addition, pretreatment of the slices with 500 microM Cd2+, but not 300 nM nimodipine, 10 microM omega-conotoxin GVIA or 10 microM MK-801, blocked the K(+)-induced change in phosphorylation. These results suggest that K(+)-induced changes in the phosphorylation of MARCKS and neuromodulin are mediated by Ca(2+)-dependent mechanisms other than, or in addition to, those sensitive to the organic Ca2+ channel antagonists employed.

Homovanillic acid in caudate and pre-frontal cortex following acute and chronic neuroleptic administration.

Homovanillic acid (HVA) was measured in rat caudate and pre-frontal cortex after single and repeated doses of several types of neuroleptic drugs. Twice daily administration of low or high doses of haloperidol, fluphenazine, or (-) sulpiride resulted in greater tolerance to the initial HVA increase in caudate compared to prefrontal cortex.

Homovanillic acid in rat caudate and prefrontal cortex following phencyclidine and amphetamine.

Phencyclidine (PCP) and d-amphetamine (AMP) had different effects upon homovanillic acid (HVA) levels in rat prefrontal cortex as compared to caudate. Lower doses of PCP increased HVA in prefrontal cortex only while lower doses of AMP decreased HVA in caudate alone. Higher doses of both drugs produced a decreased HVA in caudate and an increase in prefrontal cortex. At some doses PCP may selectively activate mesocortical dopaminergic neurons.

Activation of forebrain dopamine systems by phencyclidine and footshock stress: evidence for distinct mechanisms.

Phencyclidine combined with footshock stress produced a greater increase in the homovanillic acid content of prefrontal cortex than either phencyclidine or footshock alone. Phencyclidine decreased both substance P and substance K in the ventral tegmental area. The results suggest that phencyclidine and footshock activate forebrain dopaminergic systems in part by separate mechanisms.

Regional homovanillic acid levels and oral movements in rats following chronic haloperidol treatment.

Rats with more severe orofacial movements after 51 days of haloperidol administration showed lower levels of the dopamine metabolite homovanillic acid (HVA) in the caudate compared to animals who did not develop significant mouth movements. This effect was not observed in other brain regions sampled. This finding is consistent with the hypothesis that dopaminergic receptor supersensitivity in neostriatal structures plays some role in the development of orofacial movements in rats, in association with chronic neuroleptic administration.

Regional brain homovanillic acid following delta 9-tetrahydrocannabinol and cocaine.

delta 9-Tetrahydrocannabinol (10 mg/kg) increased homovanillic acid in rat prefrontal cortex and olfactory tubercle. This dose did not affect homovanillic acid in the caudate. Higher doses increased homovanillic acid in all 3 regions. Cocaine (20, 30, or 50 mg/kg) did not affect homovanillic acid in any of these brain regions.

Correlates of early neuroleptic response using a uniform haloperidol dose.

Twenty-one patients hospitalized for acute non-organic psychosis were treated with a fixed daily dose of haloperidol (0.2 mg/kg) for 10 days. Serum levels of haloperidol were significantly lower in the male patients at steady state as compared to females. Serum levels at 24 h and 48 h were highly correlated steady-state levels. Haloperidol levels at steady state were significantly correlated with global outcome at 10 days. Prolactin at haloperidol steady state was significantly related to global outcome at 10 days in the males. Pretreatment plasma free HVA but not MHPG was significantly related to outcome in males and females.

Elevated plasma homovanillic acid in depressed females with melancholia and psychosis.

Plasma free homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured before drug treatment in 29 patients diagnosed as having major depression with melancholia and in 18 control subjects. Plasma HVA was significantly elevated in the total group of female melancholic patients when compared with female controls or male melancholics. Most female patients with psychotic melancholia had elevated HVA levels. These differences were not found in male patients. No significant differences were found for plasma MHPG.

Phosphatase resistance of ERK2 brain kinase PK40erk2.

We have previously shown that a brain protein kinase, termed PK40, catalyzes the multiple phosphorylation of the KSP-repeat site of neurofilaments (NFs) and also can transform tau proteins into the paired helical filament-like state as found in Alzheimer's disease (AD) brains. Protein sequence analysis suggests that PK40 is a form of the extracellular signal-regulated kinase ERK2. A subpopulation of ERK2 species in soluble brain fractions can be efficiently phosphorylated and activated in cell-free systems, simply by adding Mg(2+)-ATP. Two phosphoisoforms of PK40erk2 are formed in this process, which have a reduced gel mobility, very much like the ERK2 form obtained in cell culture by stimulation with growth factors. One of these low-mobility forms cannot be inactivated with protein phosphatase 2A (PP2A) or with tyrosine phosphatases. The second form can be slowly inactivated by PP2A. In this case two Ser/Thr phosphates are removed at different rates during inactivation: One phosphate is very quickly removed to result in the formation of a high-mobility 39-kDa ERK2 species without consequence for activity; the other, slowly removed Ser/Thr phosphate controls the activity but has no effect on the gel mobility of ERK2. These results show that forms of ERK2 exist with properties different from the previously characterized ERK2 (p42mapk) from stimulated cell cultures. The active ERK2 forms produced in the presence of Mg(2+)-ATP alone could provide an explanation for the existence of constitutive ERK2-like NF phosphorylation in vivo. Excessive formation of an ERK2 species resistant to inactivation by PP2A might be relevant to the persistent pathological tau hyperphosphorylation in AD.

Early neuroleptic response: clinical profiles and plasma catecholamine metabolites.

Forty-seven psychotic inpatients who required neuroleptic treatment were studied with respect to some clinical and biochemical variables associated with early neuroleptic response. Compared to poor early responders, good responders were older at onset of illness and at index admission, less likely to have had a schizoid developmental history, and more likely to be married. There was a trend for good early responders to have received a diagnosis of affective psychosis or atypical psychotic disorder rather than schizophrenia or schizophreniform disorder. However, no behavioral symptom or sign differentiated good from poor early responders with the possible exception of pretreatment psychomotor retardation, which showed some association with poor response. Fasting plasma-free homovanillic acid was significantly higher in the good response group and 3-methoxy-4-hydroxyphenethylene glycol showed a similar trend.

High affinity binding of a potassium channel agonist to intact rat insulinoma cells.

The specific binding of a novel tritiated K+ channel opener, [3H]BAY X 9228, has been characterized in a rat insulinoma (RINm5F) cell line. The KD was 2.1 nM and Bmax 50 fmol/mg total protein as determined by saturation analysis. The high affinity binding to intact cells was inhibited by pinacidil and by a series of BAY X 9228 analogs with an activity sequence correlating well with that for producing glyburide-reversible relaxation of partially depolarized rat aorta. This represents the first report of the specific binding of a K+ channel opener to cultured cells.

Phosphorylation-dependent monoclonal Tau antibodies do not reliably report phosphorylation by extracellular signal-regulated kinase 2 at specific sites.

Analysis of phosphorylation of tau, the microtubule-associated proteins hyperphosphorylated in Alzheimer's disease, is often performed using phosphorylation-sensitive monoclonal antibodies thought to report the presence or absence of one or two specific phosphorylations (cognate sites). Using several such antibodies we found a much more complicated relationship between phosphorylation at specific sites, as monitored by two-dimensional phosphopeptide mapping, and antibody recognition of these sites. Multiple phosphorylation of tau in several stages by the brain extracellular signal-regulated kinase 2 isoform PK40 suggested that phosphorylation at cognate sites is sometimes necessary (but not sufficient) to induce a change of antibody reactivity and in some cases is not even necessary in the background of multiple phosphorylation at other sites. No single phosphorylation site was found to be responsible for any level of gel mobility shift associated with phosphorylation. Tau acquired its maximal gel mobility retardation and final immunochemical profile at substoichiometric phosphorylation of most sites. This suggests that many alternate phosphorylation patterns can produce the same conformational and immunochemical presentation on sodium dodecyl sulfate-gel electrophoresis. Although PK40(erk2) prefers some phosphorylation sites, most notably Ser235, followed by Ser199 or Ser202 and Thr205, the phosphorylation of multiple Ser/Thr-Pro sites is not highly sequential. Ser396 is one of the least preferred sites and seems to require prior phosphorylation at Ser404.