Modification of ligand binding to membranes by a soluble acceptor. Alpha-1-acid glycoprotein attenuates 3H-imipramine binding to cerebral membranes

The effect of individual plasma proteins on the binding of 3H-imipramine (3H-IMI) was investigated, using rat cerebral membranes as the binding site source. Addition of alpha-1-acid glycoprotein (aAGLP) to an incubation medium containing 4 nm 3H-IMI resulted in a concentration-dependent inhibition of 3H-IMI binding, with an IC50 value of 0.53 microM. Albumin (0.7 mM) and gamma globulin (3 microM) had no apparent effect. Scatchard analyses of 3H-IMI binding in the presence and absence of 0.5 microM aAGLP revealed that the inhibition of 3H-IMI binding was associated with an increased Kd, with no appreciable change in Bmax. The inhibitory action of platelet-free plasma (PFP) on 3H-IMI binding to cerebral membranes was eliminated after treatment of PFP with specific antibodies to aAGLP. It is suggested that the inhibition of 3H-IMI binding to cerebral membranes by PFP is due, at least partially, to the presence of aAGLP in the plasma. The observed inhibitory effect is consistent with a competition for the ligand between the membrane binding site and the soluble protein acceptor. These findings may explain the serum effect confounding radioreceptor assays of various drugs.

Inhibition of 3H-imipramine binding by plasma from depressed and normal subjects

The inhibition by human plasma of 3H-imipramine (3H-IMI) specific binding to rat cerebral membranes was investigated using platelet-free plasma (PFP) from normal and depressed subjects. The specific binding of 3H-IMI at a ligand concentration of 4 nM decreased with increasing PFP volumes, reaching 50% inhibition following the addition of 10-13 microliters PFP to a final incubation volume of 250 microliters. The extent of this inhibition was the same using PFP from controls or depressed patients. The inhibitory activity was associated with plasma proteins. Scatchard analysis of 3H-IMI binding in the presence and absence of PFP indicated that the inhibitory effect was associated with an increased Kd without an appreciable change in Bmax. It is suggested that an endogenous acceptor in the PFP, such as alpha 1-acid-glycoprotein may be responsible for the observed inhibition of 3H-IMI binding to the cerebral membranes.

Decline of GABA uptake in the hamster preoptic area following light offset

The uptake of gamma-aminobutyric acid (GABA) was studied in homogenates of the accumbens-preoptic region (APR) of the hamster brain. Aggressive and non-aggressive female hamsters, maintained under a reversed 10-h dark and 14-h light cycle were sacrificed at various times after light offset. Aliquots of the APR homogenates were incubated with a series of [3H]GABA concentrations to obtain values for Vmax and Km. In both groups Vmax values declined sharply after light offset. The reduction in GABA uptake from early to later dark phase parallels the routine diminution in the aggressive activity of rodents from its peak in the early dark phase; the increase in GABAergic inhibition which presumably results from the reduced uptake may contribute to this change in aggressive activity.

Effect of membrane protein concentration on binding of 3H-imipramine in human platelets

Binding of 3H-imipramine to platelet membranes has been implicated as a marker for depression. Comparing 3H-IMI binding between depressed patients and normal subjects we observed an increase in the dissociation constant Kd with increasing membrane protein. This phenomenon was studied more rigorously in five normal subjects. Platelet membranes were prepared and adjusted to four concentrations of protein ranging from 100 to 800 micrograms/ml. The 3H-IMI binding parameters of maximum binding sites number (Bmax) and Kd were obtained by Scatchard analysis at each membrane concentration. A positive linear relationship was found between Kd values and the concentration of membrane protein in the assay, but no change was observed in Bmax. The variability in Kd values reported in the literature may be accounted for in part by the different concentrations of membrane protein used in various studies.

Attenuation by electroshock treatment of the haloperidol-induced rise in the binding of 3H-imipramine to rat brain membranes

Studies were conducted in rats to investigate whether chronic haloperidol treatment, electroshock treatment (EST), or a combination of both affects the high-affinity binding of 3H-imipramine to cerebral membranes. Chronic haloperidol (2 mg/kg SC daily for 28 days) resulted in a significant decrease in the density of binding sites in animals killed 1 h after the last treatment, but binding was markedly enhanced after a "washout" period of 5 days. In animals subjected to EST (20-30 mA, 1.5 s, 60 Hz; three times a week for 4 weeks) and killed 1 h after the last treatment, there were no apparent changes, but when animals were allowed a recovery period of 5 days there appeared to be a slight increase in binding. The marked increase in binding seen after haloperidol withdrawal was no longer apparent in animals treated with both haloperidol and EST, indicating that EST acts to attenuate the increase in binding seen after withdrawal of chronic haloperidol. It is suggested that chronic haloperidol may influence presynaptic recognition sites that regulate serotonin uptake and that EST may interact with haloperidol to "stabilize" these presynaptic sites.

High affinity 3H-imipramine binding in human platelets: age and sex effects

Age and sex effects on 3H-imipramine platelet binding sites were determined in 58 normal subjects (27 males, 31 females). The correlation of age with either the maximal imipramine binding (Bmax) or the dissociation constant (Kd) was statistically nonsignificant in both males and females. Males did not differ from females in Bmax and Kd values. The implications for psychiatric research were discussed.

Dopamine and serotonin metabolites in rat cerebroventricular fluid following withdrawal of haloperidol or electroshock treatment

Levels of the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and of the major serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) were determined in the CSF of rats at various times after repeated electroshock treatment (EST) or chronic administration of haloperidol. The acidic metabolites were analyzed in 25 microliter CSF using HPLC with an electrochemical detector. A significant decrease in the CSF levels of DOPAC and HVA was found 4 days after the last administration of chronic haloperidol, EST, or both. The decrease in the level of the dopamine metabolites indicated a slower dopamine turnover, which might have resulted from hypersensitivity of presynaptic dopamine receptors after these treatments. Rats treated with haloperidol also showed an increase in 5-HIAA levels, possibly due to enhanced serotonin turnover. The 5-HIAA increase following haloperidol was prevented by a concurrent administration of EST, suggesting attenuation by EST of the haloperidol-induced enhancement of serotonin turnover.

Effects of carbamazepine and anti-depressant drugs on endogenous catecholamine levels in the cerebroventricular compartment of the rat

Concentrations of endogenous norepinephrine, dopamine and epinephrine in cerebroventricular perfusates were used to evaluate the effects of drugs on the availability of extracellular catecholamines in the intact rat brain. Administration of the antidepressant drugs imipramine, desmethylimipramine or tranylcypromine resulted in marked increases of both norepinephrine and dopamine concentrations while epinephrine levels were not affected. Treatment with a similar dose of carbamazepine - an anticonvulsant drug with antidepressant activity - resulted in a significant increase in dopamine concentrations without apparent effect on either norepinephrine or epinephrine. It is suggested that at the applied dose, carbamazepine may act to modify the uptake, release or metabolism of dopamine in brain areas adjacent to the cerebroventricular space without affecting the other catecholamines.

3H-imipramine platelet binding sites in unipolar depression

High-affinity 3H-imipramine binding to platelets was determined in 15 drug-free unipolar depressed women and 15 normal controls. The maximum number of binding sites (Bmax) was lower in the depressed population, but the difference fell short of statistical significance (p = 0.07). The dissociation constant for imipramine binding (Kd) was found to be significantly lower among patients than in controls (p = 0.02). The various factors that can affect the in vitro platelet assay, and the implications for affective disorder research, were discussed.

Measurement of tritiated norepinephrine metabolism in intact rat brain

A procedure for the study of NE metabolism in the intact rat brain is described. The method involves ventriculocisternal perfusion of the adult male rat with artificial CSF containing [3H]NE. Radioactivity in the perfusate associated with NE and its metabolites 3,4-dihydroxymandelic acid (DOMA), 3,4-dihydroxyphenylethyleneglycol (DHPG), 3-methoxy-4-hydroxymandelic acid (VMA), 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), and normetanephrine (NMN) is separated using high-performance liquid chromatography (HPLC). After 80 min the radioactivity in the perfusate reaches an apparent steady-state. Analysis of the steady-state samples shows higher activity in the fractions corresponding to DHPG and MHPG than in those corresponding to DOMA and VMA, confirming glycol formation as the major pathway of NE metabolism in rat brain. Pretreatment with an MAO inhibitor (tranylcypromine) results in a marked decrease in the deaminated metabolites DHPG and MHPG and a concurrent increase in NMN. The results indicate this to be a sensitive procedure for the in vivo determination of changes in NE metabolism.

Apparent turnover of norepinephrine in the intact rat brain estimated from its rate of appearance in the cerebroventricular compartment

The apparent turnover of norepinephrine (NE) in the intact brain of urethane-anesthetized rats was estimated in vivo from the rate of appearance of endogenous NE in the cerebroventricular compartment. Ventriculocisternal perfusion, a radioenzymatic assay for endogenous NE and isotope dilution of 3H-NE were used to determine the rate of appearance (Ra) of NE. The effect of tranylcypromine, a monoamine oxidase (MAO) inhibitor and releasing agent on Ra of NE, was also studied. In control animals, the mean Ra value was 0.40 pmol/min. Pretreatment with tranylcypromine resulted in a threefold increase in the mean value for Ra, which was due to increased secretion of NE into the CSF. The results indicate that 90% of the NE entering the cerebroventricular compartment was removed. Pretreatment with tranylcypromine did not modify removal, thus suggesting that tranylcypromine has no effect on the physiological processes which regulate the removal of NE from the CSF.

Reconstruction of mandible with pedicle bone grafts

Three cases of pedicle bone grafts used to reconstruct the mandible are presented. The grafts were taken from the shoulder blade, rib and clavicle. In two patients partial and in one patient total mandibles were reconstructed. Good results were obtained.

[Functional disorders following resection of the tongue and mouth floor]

On observing 20 patients who had underwent total tongue and floor-of-the-mouth resection, the authors stated difficulties in swallowing and breathing that in certain cases called for laryngectomy. To counteract these disorders, floor-of-the-mouth and tongue reconstruction was performed with the aid of an arterialized frontal flap, which resulted in essentially undisturbed functions.