Naloxone effects on beta-endorphin, cortisol, prolactin, growth hormone, HVA and MHPG in plasma of normal volunteers

Acute and chronic effects of neuroleptic drugs on plasma and brain homovanillic acid in the rat

In the rat, the acute administration of the neuroleptic drug, haloperidol, produces a parallel increase in brain and plasma concentrations of the dopamine metabolite, homovanillic acid (HVA). The effect of other neuroleptic drugs, which may differ from haloperidol in their central and peripheral actions, on brain and plasma HVA has not been systematically investigated. Therefore, in this report we examine the acute effects of six different neuroleptic drugs, representing most major chemical classes of these drugs, on plasma and brain concentrations of HVA. Metoclopramide, fluphenazine, loxapine, and molindone produce parallel increases in brain and plasma HVA which closely resemble those produced by haloperidol. Compared to these neuroleptics, chlorpromazine produces a much greater increase in plasma HVA but a similar effect on brain HVA. The large chlorpromazine-induced increase in plasma HVA suggests that this drug alters peripheral production or clearance of HVA, perhaps via blockade of peripheral alpha-receptors. Of the available neuroleptics, sulpiride is one of the most specific and potent at blocking the dopamine vascular receptor. Administration of high doses of sulpiride produces only modest increases in both plasma and brain HVA, suggesting that blockade of peripheral dopamine receptors does not substantially alter peripheral clearance of HVA. After chronic administration of haloperidol for up to 21 days, plasma HVA continued to reflect the brain HVA response to drug administration.

The effects of chronic naloxone on pituitary hormone secretion in female rats

The effects of a sustained-release implant for naloxone (NAL) on serum concentrations of prolactin (PRL), immunoreactive beta-endorphin (IR-beta-ENDO), growth hormone (GH) and thyroid stimulating hormone (TSH) were evaluated in ovariectomized female rats. After 9 days of exposure to NAL, serum levels of none of these 4 pituitary hormones were altered. However, the NAL implant antagonized the stimulatory effects of morphine (15 and 30 mg/kg body weight) on PRL and IR-beta-ENDO secretion, enhanced the stimulatory effects of morphine on GH secretion, and had no effect on morphine-induced suppression of TSH secretion. These results indicate that while chronic NAL exposure does not, by itself, persistently alter pituitary hormone secretion, it differentially effects the response of these hormones to morphine exposure. These data suggest that chronic treatment with narcotic antagonists may invoke differential compensatory mechanisms to maintain normal hormone secretion.

Effects of naltrexone on plasma corticosterone in opiate-naive rats: a central action

We have previously reported the elevation of plasma corticosterone by i.v. naloxone HCl (NX). This work has been extended, with the current study, showing a similar effect with naltrexone HCl (NTX) and that this effect is due to a central action of the drug. Using opiate-naive male rats with chronic i.v. catheters, stereotaxically placed intracerebroventricular (ICV) cannula guides where necessary, and sound-attenuated one-way vision boxes, serial blood samples were obtained from conscious unrestrained animals. NTX (5.0, 10.0, or 20.0 mg/kg i.v.) resulted in a significant increase in plasma corticosterone 15 min following injection. I.V. administration of the methylbromide salts of each drug, which do not cross the blood-brain barrier, did not produce this same elevation in hormone level at several doses (0.4, 1.0, 2.0, 10.0 or 20.0 mg/kg). In contrast, ICV injection of either of the quaternary salts (50 micrograms/10 microliter/animal) resulted in an immediate and sustained rise in plasma corticosterone. Results obtained demonstrate that NTX has a similar effect on plasma corticosterone as NX at the appropriate doses and that the effect is a central rather than a peripheral one.

The effects of diet and physical activity on plasma homovanillic acid in normal human subjects

This study examines the effect of diet and moderate physical activity on plasma levels of the dopamine metabolite homovanillic acid (HVA) in healthy young males. At weekly intervals, subjects were fed four isocaloric meals: polycose (pure carbohydrate), sustecal, low monoamine, and high monoamine. Moderate physical activity consisted of 30 minutes of exercise on a bicycle ergometer. The effect of diet on plasma HVA (pHVA) was highly significant. Compared to the polycose meal, the high monoamine meal significantly increased pHVA. Moderate physical activity also significantly increased pHVA. Future clinical studies using pHVA in man as an index of brain dopamine function should control for the effects of both diet and physical activity.

High-dose naloxone affects task performance in normal subjects

Increasing intravenous doses of naloxone (0.3 mg/kg, 1 mg/kg, and 2 mg/kg) were administered to normal subjects. Naloxone at 2 mg/kg, but not at lower doses, impaired aspects of memory as measured by a verbal learning task which assessed the direct free recall and recognition of presented versus non-presented words of a single category (effortful processing) and the monitoring of the frequency of such presentations (automatic processing). At the same time "working" memory was left unaffected. The results suggest a role for the opioid system in some memory processes in man.

Endorphin levels in opioid-dependent human subjects: a longitudinal study

Endorphin levels were measured in 51 cerebrospinal fluid samples from 27 opioid-dependent or postdependent subjects. Radioreceptor assay showed the endorphin levels to be higher than those found in normal subjects. These high levels were found even while subjects were on methadone maintenance. The duration of opioid dependence was positively correlated with fraction I values. Both fractions tended to be lower during early withdrawal than late withdrawal. In naltrexone-maintained patients, radioreceptor assay showed FII to be greatly elevated, but electrophoresis and HPLC indicated that the elevations were not due to a peptide. Thus, the possibility of unextracted naltrexone metabolites remains at least a partial explanation for this apparent FII elevation.

Naloxone, tardive dyskinesia, and endogenous beta-endorphin

The subjects were 13 psychiatric inpatients with tardive dyskinesia. Each subject participated in two sessions. Either naloxone (10 mg) or placebo was administered intravenously during each session. In a subset of subjects (n = 7), blood samples for beta-endorphin were drawn before and at 30 and 60 minutes after the injection. The Abnormal Involuntary Movement Scale was administered before and at 10, 20, 40, 60, 120, and 360 minutes after the injection. Double-blind procedures were maintained throughout the experiment. Neither naloxone nor placebo had any appreciable effect on the involuntary movements. Naloxone elicited a significant increase in the plasma beta-endorphin.

Endogenous opiates: 1981

This paper is the fourth of an annual series reviewing the research concerning the endogenous opiate peptides. This installment covers only work published during 1981 and attempts to provide a comprehensive, but not exhaustive, survey of the area. Previous papers in the series have dealt with research done before 1981. Topics concerning endogenous opiates reviewed here include a delineation of their receptors, their distribution, their precursors and degradation, behavioral effects resulting from their administration, their possible involvement in physiological responses, and their interactions with other peptides and hormones. Due to the burgeoning literature in this field, the comprehensive nature of this review in the future will be limited to considerations of behavioral phenomena related to the endogenous opiates.

Naloxone in chronic schizophrenic patients: neuroendocrine and behavioral effects

Naloxone produced improvement in abnormal thought content in medicated chronic schizophrenic patients, but not in drug-free patients. In contrast, drowsiness and increases in plasma prolactin concentrations were seen only in drug-free schizophrenic patients. Although growth hormone concentrations increased in drug-free and medicated schizophrenic patients, the time course was different in the two groups. Neuroleptics appear to alter naloxone's clinical and neuroendocrine effects in chronic schizophrenic patients.

The effect of naloxone on normal human sleep

Placebo and naloxone (4, 8, and 12 mg) were infused on separate nights in a double-blind fashion over a 20-min period between the 25th and 45th min of sleep in normal volunteers. Naloxone produced a dose-dependent increase in REM latency (the time from onset of sleep until the first REM period), and duration of the first REM period and second NREM period. The number of REM periods was also reduced.

Physiological effects of high dose naloxone administration to normal adults

The intravenous bolus administration of high doses of the opioid receptor antagonist naloxone (in the mg./kg. range) to normal adults produced dose-dependent increases in systolic blood pressure and respiratory rate. No significant alterations in other physiological processes were found although there were trends for increases in oral temperature and pulse rate with increasing dose. These results suggest the involvement of an endogenous opioid system in the tonic regulation of human systolic blood pressure and respiration and the probable inadequacy of doses of naloxone previously utilized in human studies to effect complete blockade of endogenous opioid systems.

Relationship between urinary free cortisol and CSF opioid binding activity in depressed patients and normal volunteers

We investigated the relationship between hypothalamic-pituitary-adrenal (HPA) activity, as measured by 24-hour mean urinary free cortisol (MUFC), and cerebrospinal fluid (CSF) opioid activity in patients with major affective disorder and normal volunteers. Among depressed patients, but not normal volunteers, mean 24-hour urinary cortisol values were significantly correlated with CSF opioid activity measured by radioreceptor assay, but were not significantly correlated with beta-endorphin immunoreactivity measured by radioimmunoassay. MUFC, as expected, was significantly higher in depressed patients than in normal volunteers. Mean values of CSF opioid activity and beta-endorphin immunoreactivity did not differ significantly in the two groups. The positive opioid-MUFC correlation found in the depressed group appeared to depend on patients who were cortisol hypersecretors. These data, using relatively crude measures of cortisol and opioid activity, are suggestive of a relationship between these two systems, particularly under "activated" conditions such as those observed in depression.