Inhibition of 5-hydroxytryptamine reuptake by amitryptyline an zimelidine and its relationship to their therapeutic action.

Amitriptyline and zimelidine significantly reduce the uptake of 5-HT into the blood platelets of depressive patients. The degree of inhibition is significantly correlated with the plasma drug level of amitriptyline. No significant relationship could be detected between the degree of inhibition of uptake and therapeutic outcome. The accepted mode of action of tricyclic antidepressant drugs and the deficiency hypotheses of affective disorders are discussed.

Zimelidine: a therapeutic and pharmacokinetic study in depression.

Zimelidine, a bicyclic compound with a strong effect on the neuronal reuptake of 5-hydroxy-tryptamine and with weak anticholinergic actions, was evaluated for its antidepressant efficacy in a double-blind comparative trial with amitriptyline. In doses of 200 mg a day it was found to be as effective as 150 mg amitriptyline, but with significantly less subjective side-effects. The plasma concentration of zimelidine and its metabolite, norzimelidine, showed no significant correlation with therapeutic outcome.

Platelet 5-hydroxytryptamine accumulation in depressive illness.

The uptake of 5-hydroxytryptamine (5-HT) by blood platelets from controls, depressed patients and recovered depressed patients has been determined using short incubation times and low substrate concentrations. The affinity of serotonin for the platelet membrane appears to be normal in acutely depressed and recovered depressed patients. The capacity of transport of 5-HT through the platelet membrane is impaired in these depressive patients and this impairment is independent of the psychiatric status of the patients and is discussed in the light of the electrolyte and enzyme disturbances that are associated with depressive illness.

Decreased tryptophan excretion by depressive patients.

The concentration and 24-h urinary excretion of tryptophan has been measured in urine samples from monopolar female depressed patients and female control subjects. Female depressed patients and the control subjects excrete similar amounts of tryptophan. Patients with endogenous features of depression excrete significantly less tryptophan in 24 h than do the patients with reactive features and the control subjects. The relationship between plasma tryptophan concentration and 24-h urine tryptophan excretion in control subjects has been investigated and the results discussed in the light of abnormalities of tryptophan metabolism in depressive illness.

Comparison of methods for the determination of total and free tryptophan in plasma.

A comparison is made between two fluorimetric techniques for the determination of total and free plasma tryptophan. Comparison is also made between methods for the separation of the unbound and bound fraction of plasma tryptophan using ultrafiltration, Centricones and small-scale equilibrium dialysis.

Tryptophan accumulation by blood platelets of depressed patients.

The accumulation of tryptophan by blood platelets has been investigated in depressive patients and controls using short incubation times and low substrate concentrations. The accumulation of tryptophan by the platelet is significantly greater in the acutely depressed patients than the control group. The results are discussed with reference to tryptophan transport in depression and also to the regulation of plasma levels of tryptophan.

Seasonal variations in biochemical factors related to depressive illness.

Biochemical variates that may be related to depressive illness have been shown to vary significantly according to the season. This factor must therefore be carefully considered in biochemical and therapeutic investigations into depression, and may account for the seasonal variation in depression and suicide that have been reported by many investigators.

Folic acid enhances lithium prophylaxis.

A double-blind trial was carried out to investigate the effect on affective morbidity of a daily supplement of 200 micrograms folic acid or a matched placebo in a group of 75 patients on lithium therapy. During the trial the patients with the highest plasma folate concentrations showed a significant reduction in their affective morbidity. Patients who had their plasma folate increased to 13 ng/ml or above had a 40% reduction in their affective morbidity. It is suggested that a daily supplement of 300-400 micrograms folic acid would be useful in long-term lithium prophylaxis.

Apparent supersensitivity of platelet 5-HT receptors in lithium-treated patients.

An increased 5-HT-induced platelet aggregatory response was seen in bipolar and unipolar patients who were being treated with lithium prophylactically. The responses were not related to the patients' lithium levels or affective morbidity. The results are discussed with reference to the action of antidepressive treatments on 5-HT receptor systems in the platelet and the CNS.

Seasonal variations in the dexamethasone suppression test.

One hundred and fifty-six patients from Epsom (U.K.) and Brussels, all suffering from major depressive disorder, were tested on the dexamethasone suppression test. Post-dexamethasone cortisol concentration in the plasma was found to be much lower in the winter months (November to February) than in the rest of the year.

Peripheral serotonergic receptor sensitivity in depressive illness.

Platelet aggregation induced by 5-HT was used as a measure of the functional responsiveness of peripheral 5-HT receptors in controls and drug-free depressed patients. No significantly different aggregatory response (5-HT/ADP ratio) was noted between the controls and drug-free depressed patients. If the receptor mediating this response is a 5-HT2 receptor, there is no overwhelming evidence to suggest that the functional activity of this system is abnormal during a depressive illness. The results are discussed with reference to reported abnormalities of 5-HT2 receptors during a depressive illness and to their change during antidepressant treatment.

Depression and tetrahydrobiopterin: the folate connection.

Total biopterin, neopterin and creatinine were measured in spot urine samples from affective disorder patients on lithium therapy and control subjects. Folic acid was also measured in plasma in a sample of the patients. The mean neopterin: biopterin ratio was significantly higher in the 76 patients (3.2 +/- 0.5) than in the 61 controls (1.8 +/- 0.1). In female patients biopterin levels were significantly lower than in controls. In the control groups there was a significant correlation between the molar concentration of neopterin and biopterin. No such correlation was found in the patients. These data indicate that tetrahydrobiopterin (BH4) biosynthesis is reduced in this group. A significant positive correlation was found between plasma folate and urinary biopterin. It is suggested that folate deficiency may impair the synthesis of BH4, a cofactor essential for the synthesis of 5-HT and other monoamines that are involved in the pathogenesis of affective disorders.

Mianserin in the prophylaxis of migraine: a double-blind study.

Evidence is reviewed indicating that instability in central nervous system handling of 5-hydroxytryptamine may be of primary importance in the pathogenesis of migraine, and that the observed diminution of platelet content and uptake of 5-hydroxytryptamine related to an attack may merely be a reflection of this. The rationale is discussed for selecting mianserin as a potentially effective migraine prophylactic based on: (i) its ability to restore to normal platelet 5-hydroxytryptamine uptake when this is decreased in depression; (ii) its effect on the central nervous system; and particularly (iii) its antiserotonergic activity. A double-blind control trial of mianserin versus placebo in the prophylaxis of migraine is described. There was a significant fall in both frequency and severity of migraine attacks when compared with baseline values in mianserin-treated patients but not in placebo-treated patients. There was no accompanying change on the Beck Depression Inventory. It is concluded that mianserin is an effective migraine prophylactic in some patients. There is no evidence indicating which pharmacological property of mianserin is responsible for this effect.

The action of antidepressant drugs on 5-hydroxy-tryptamine uptake by platelets--relationship to therapeutic effect.

The uptake of 5-hydroxytryptamine (5-HT) by the blood platelets of depressive patients treated with amitriptyline and zimelidine has been examined. Both drugs significantly reduce the uptake of 5-HT into the platelet and the degree of inhibition is correlated with the plasma drug level of amitriptyline. No significant correlations could be detected between the degree of inhibition of uptake and clinical change. The accepted mode of action of tricyclic antidepressant drugs, i.e. the inhibition of reuptake of released amines, is discussed.

Lithium restores abnormal platelet 5-HT transport in patients with affective disorders.

Kinetic analysis of the transport of 5-HT into the blood platelets of depressed patients and recovered depressive patients has shown that the rate of accumulation of 5-hydroxytryptamine (5-HT) is significantly decreased both before and after recovery from the illness. This abnormality is corrected by both short and long-term lithium treatment. As a corollary to these studies, the effect of lithium in vitro on 5-HT uptake has been studied and the results are opposite to those reported in vivo. These findings suggest that lithium acts indirectly, and possible mechanisms of its action are discussed.

Effect of mianserin hydrochloride on peripheral uptake mechanisms for noradrenaline and 5-hydroxytryptamine in man.

1. Mianserin seems to have little effect on peripheral noradrenaline (NA) re-uptake mechanisms as shown by its lack of effects on the tyramine dose and NA dose/pressor response. 2. Mianserin has no effect on the hypotensive action of bethanidine. 3. Mianserin in vivo has a significant action on platlet transport (Vmax) of 5-hydroxytryptamine (5-HT), which changes toward normal values in depressive patients on the drug. This action is not observed in vitro. 4. It is possible that a metabolite of mianserin is responsible for this effect, and that this may be of therapeutic importance.

Blood platelet 5-hydroxytryptamine accumulation and migraine.

The active uptake of 5-hydroxytryptamine (5-HT) by platelets from migraine patients was measured and the results compared with 5-HT uptake of platelets from normal subjects. No significant differences in platelet 5-HT uptake were found between migraine patients and control subjects. A significant correlation was found between the length of time since the patients last migraine attack and Vmax (maximal rate of 5-HT transport). Patients who had a headache within five days prior to the test had significantly lower values of Vmax than patients without recent headaches. The implications and possible causes of this reduction in platelet 5-HT transport are discussed.

Drug plasma levels and platelet 5-HT uptake inhibition during long-term treatment with fluvoxamine or lithium in patients with affective disorders.

1 Plasma levels and platelet 5-HT uptake characteristics were determined at baseline and at various times during a long-term study comparing fluvoxamine and lithium prophylaxis. 2 In the fluvoxamine-treated patients after 12 and 24 weeks of treatment, Km was significantly increased and y, the mean overall uptake, significantly decreased compared to the patients' own baseline values and to lithium treatment. No significant change was noted for Vmax. 3 For fluvoxamine, significant negative relationships were established between the Vmax of platelet 5-HT uptake and plasma levels. 4 The trial had to be discontinued prematurely for some patients due to apparent lack of efficacy, unwanted effects or a combination of both in the fluvoxamine-treated patients. Low plasma levels of fluvoxamine may have contributed to the apparent lack of prophylactic efficacy of the drug. 5 Reference is made to the activity of receptor systems in patients receiving lithium and the consequent changes occurring after the administration of a potent 5-HT re-uptake inhibitor.