The psychopharmacology of the human pineal

N,N-dimethyltryptamine and Amazonian ayahuasca plant medicine

OBJECTIVE

Reports have indicated possible uses of ayahuasca for the treatment of conditions including depression, addictions, post-traumatic stress disorder, anxiety and specific psychoneuroendocrine immune system pathologies. The article assesses potential ayahuasca and N,N-dimethyltryptamine (DMT) integration with contemporary healthcare. The review also seeks to provide a summary of selected literature regarding the mechanisms of action of DMT and ayahuasca; and assess to what extent the state of research can explain reports of unusual phenomenology.

DESIGN

A narrative review.

RESULTS

Compounds in ayahuasca have been found to bind to serotonergic receptors, glutaminergic receptors, sigma-1 receptors, trace amine-associated receptors, and modulate BDNF expression and the dopaminergic system. Subjective effects are associated with increased delta and theta oscillations in amygdala and hippocampal regions, decreased alpha wave activity in the default mode network, and stimulations of vision-related brain regions particularly in the visual association cortex. Both biological processes and field of consciousness models have been proposed to explain subjective effects of DMT and ayahuasca, however, the evidence supporting the proposed models is not sufficient to make confident conclusions. Ayahuasca plant medicine and DMT represent potentially novel treatment modalities.

CONCLUSIONS

Further research is required to clarify the mechanisms of action and develop treatments which can be made available to the general public. Integration between healthcare research institutions and reputable practitioners in the Amazon is recommended.

Serum melatonin and urinary 6-sulfatoxymelatonin in major depression

In this study, serum melatonin and urinary 6-sulfatoxymelatonin (aMT6s) were measured in 14 major depressive inpatients, compared to 14 matched controls according to age, gender, season and hormonal treatment in women. Moreover, the relationship between serum melatonin and urinary aMT6s levels was analysed in the two groups. Results indicated that the two groups of subjects showed a clear melatonin rhythm without significant difference in the mean level of melatonin or aMT6s, in the area under the curve of melatonin or in the melatonin peak. However, the time of the nocturnal melatonin peak secretion was significantly delayed in depressive subjects as compared to healthy controls. Moreover, the depressed patients showed urinary aMT6s concentrations enhanced in the morning compared to night time levels, while these concentrations were lowered from the night to the morning in the control group. These results suggest that the melatonin production is phase-shifted in major depression.

Melatonin response to atenolol administration in depression: indication of beta-adrenoceptor dysfunction in a subtype of depression

OBJECTIVE

To investigate peripheral beta-adrenoceptor sensitivity in depression by assessing urinary melatonin pre- and post-administration of atenolol.

METHOD

Overnight urinary melatonin pre- and post-administration of 100 mg oral atenolol was assessed in 36 depressed subjects and 47 controls.

RESULTS

Baseline melatonin was significantly lower in depressed patients than controls (P=0.004). Melatonin following atenolol administration was strongly reduced in both groups (P < 0.0001). This reduction depends on whether the subject is a high or low (cutoff: 0.25 nmol/l) baseline melatonin excretor (P=0.025) and on whether he is depressed being a low excretor (P=0.048). A negative correlation (P=0.007) was found between melatonin decrease after atenolol and the Montgomery-Asberg Depression Rating Scale score.

CONCLUSION

Atenolol strongly reduces melatonin in depressed and control subjects; this decrease relates inversely to the severity of depressive symptoms. Furthermore, responsiveness to atenolol differs between low melatonin depressed patients and low excretor controls, alluding to beta-adrenoceptor up-regulation in a subtype of depression.

Melatonin response to clonidine administration in depression: indication of presynaptic alpha2-adrenoceptor dysfunction

BACKGROUND

The aim of this study was to investigate alpha2-adrenoceptor sensitivity in depression, by using melatonin response to clonidine administration as an index of alpha2-adrenoceptor functioning.

METHOD

35 depressed subjects and 41 healthy controls were assessed for overnight urinary melatonin pre- and post-administration of oral clonidine.

RESULTS

Administration of clonidine significantly reduced melatonin concentrations in depressed patients but not in control subjects.

LIMITATION

A single oral dose (0.15 mg) of clonidine was administered.

CONCLUSIONS

Further indication is provided for presynaptic alpha2-adrenoceptor dysfunction in depression with the application of an alternative pharmacological challenge method.

Coadministration of melatonin and fluoxetine does not improve the 3-month outcome following ECT

At least 50% of patients with manic depressive disorder (MDD) treated successfully with electroconvulsive therapy (ECT) will experience a relapse within the first year of follow-up. Sleep disturbances are very common in MDD and may constitute forerunners of relapse. In this study we tested the hypothesis that melatonin, a sleep-promoting hormone, would decrease the 3-month relapse rate after successful ECT. We included in the study patients with MDD successfully treated with ECT (post-ECT Hamilton Rating Scale for Depression [HRSD] < or = 10). Patients were blindly randomized to two groups, one receiving fluoxetine + placebo and one receiving fluoxetine + melatonin. Assessments (HRSD, Brief Psychiatric Rating Scale, Global Assessment of Function Scale, Global Depression Scale, Pittsburgh Sleep Quality Index, Mini-Mental State Exam, and pill count) were performed for 12 weeks after ECT. Ten of the 35 patients (28.5%) relapsed during the follow-up period. Relapse rates were similar in both groups of patients. Sleep reports were not improved by melatonin. Patients who achieved a higher functional state post-ECT relapsed less often. We conclude that the addition of melatonin to on-going fluoxetine treatment did not have a beneficial effect either on the 3-month outcome post-ECT or on the sleep reports of these patients.

The effects of electroconvulsive therapy on melatonin

Although several studies have investigated the impact of various antidepressant medications on melatonin, there are no published reports addressing the effects of electroconvulsive therapy (ECT). Melatonin's major urinary metabolite, 6-sulfatoxymelatonin (6MT), was measured before and after an acute course of ECT. Fourteen subjects diagnosed with major depression who had failed prior pharmacologic therapy were enrolled. 6MT excretion was measured using an enzyme-linked immunosorbent assay test in 24 hour samples separated into daytime and nighttime components. Hamilton Rating Scale for Depression scores showed a significant improvement (p < 0.0001). Data analysis using the Wilcoxon signed rank test demonstrated a significant decrease in 24 hour 6MT post-ECT (p < 0.016) and daytime 6MT (p < 0.008). These results demonstrate an association between a therapeutic response to ECT and decrease in endogenous melatonin production.

Normative melatonin excretion: a multinational study

The present study on overnight urinary melatonin was conducted on the most geographically dispersed population to date, over a 1 year period, also covering a broad age range (18-62 years). An inverse relationship between melatonin and age, as well as between melatonin and weight was observed for both genders. Females as a whole, had higher melatonin values than males. Furthermore, the excretion of melatonin exhibited a bimodal distribution, distinguishing two groups of individuals: low and high melatonin excretors. The cut-off point was set at 0.25 nmol/l for ages up to 40 years and at 0.20 nmol/l for subjects above this age. Since melatonin may be involved in several physiological and pathological processes, it could be of importance to detect the type of melatonin excretion that prevails in various conditions, using a simple noninvasive procedure such as the overnight urinary measurement. For that purpose, this large sample could serve as a worldwide reference databank across different ages and locations.

Neuroendocrine aspects of primary endogenous depression. XV: Mathematical modeling of nocturnal melatonin secretion in major depressives and normal controls

We previously reported a trend toward a higher mean nocturnal serum melatonin (MEL) concentration, based on 30-min blood sampling over 24 h, in 23 female definite endogenous depressive compared to 23 matched normal female control subjects, and no significant difference in 15 male depressives compared to their controls (Rubin et al., 1992). In both groups of patients vs. their controls, there also were trends toward an earlier MEL rise time, by about 30 min, and a later MEL peak time, by about 90 min. Because the offset of MEL secretion was not estimated in that study, the total duration of MEL secretion could not be determined. To further delineate the nocturnal MEL secretion curve, we modeled the MEL data by a linear-Beta model, a four-parameter adaptation of the Beta function. One parameter accounted-for baseline (diurnal) MEL concentration, two accounted for the shapes of the ascending and descending phases of the nocturnal secretion curve, and the fourth accounted for the area under the curve. The model permitted estimation of the start, peak, and end times of nocturnal MEL secretion. There again was a trend toward a higher mean nocturnal MEL concentration in the female depressives compared to their matched controls. There were no significant patient-control differences in secretion onset or peak times in either the women or the men except for nocturnal MEL offset time: the female patients had a trend toward a later offset time, by about 40 min, than their controls; this difference was not present in the men. With women and men analyzed together, the difference in nocturnal MEL offset time between patients and controls just reached significance (P < 0.05). The linear-Beta model appears to satisfactorily fit the MEL data and provides estimators of the onset, peak, and offset times of the activation phase of MEL secretion. This model may be applicable to more severely skewed 24-h hormone secretion curves, such as ACTH and cortisol.

Low and high melatonin excretors among healthy individuals

To meet the need of establishing firm normative data regarding the secretion/excretion of human melatonin, nighttime urinary melatonin of 16 healthy volunteers was measured in samples collected monthly over a period of 1 year. Low melatonin excretors (N = 8) were distinguished from high melatonin excretors (N = 8), based on a cut-off mean melatonin value of 0.25 nmol/l. There was no overlap in any of the monthly melatonin values between the two groups, while their annual rhythms of melatonin excretion were not different in shape. Since no obvious factors (age, sex, height, weight, etc.) were responsible for the observed differences, the distinction between low and high nocturnal excretion and by inference secretion of melatonin most likely reflects genetically determined variable levels of the noradrenergic secretory drive and/or variable N-acetyltransferase/hydroxyindole-O-methyltransferase enzymatic activity during the night.

Plasma melatonin levels in anorexia nervosa

Plasma melatonin levels were measured at three-hourly intervals over 24 hours in 11 women with untreated anorexia nervosa, and in nine healthy women of normal weight. The circadian rhythm was unaltered but the nocturnal secretion of melatonin was significantly greater in anorectics. It is possible that this was related to nocturnal hypoglycaemia.

Seasonal affective disorder and the yoga paradigm: a reconsideration of the role of the pineal gland

Seasonal Affective Disorder is a psychiatric disorder whose pathophysiology and clinical presentation are poorly understood. By applying the ancient paradigm of yoga psychology to this subject, new understandings of the syndrome emerge regarding the possible role of the pineal gland, the clinical presentation of the syndrome, and the possible mechanism of action of phototherapy. The energy depletion model presented here ties together such diverse elements as: dose-response aspects of phototherapy, anergia as a primary symptom of SAD, 'spring fever', myofascial pain disorder, the anti-gonadotrophic effect of melatonin, and pineal supersensitivity in bipolar patients. Clinical predictions are made, and simple research protocols are suggested which can directly test the hypotheses generated by this paradigm.

The effect of moderate weight loss on overnight melatonin secretion

Overnight plasma melatonin level was measured in ten healthy women before and after a 4300 kJ (1000 kcal) diet in which they lost an average 3.1 kg. This weight loss did not significantly alter melatonin levels.