Reduced diazepam binding following chronic benzodiazepine treatment.

Specific ³H-diazepam binding was measured in rat cortex after 7–10 days of twice daily injection of a large dose of flurazepam. Compared to cortex taken from saline treated controls, there was a statistically significant decrease of about 15% in the maximum binding capacity (B_max). There was also a change in the dissociation constant (K_D) from 5.27 to 8.80 nM. Repeated washing of the tissue sample before the binding assay showed that the B_max was truly decreased in the treated animals, but the change in K_D was probably an artifact due to residual flurazepam remaining in the tissue that interfered with the binding assay. It is concluded that chronic benzodiazepine treatment caused an apparent decrease in the number of specific binding sites.     

No changes in rat benzodiazepine receptors after withdrawal from continuous treatment with lorazepam and diazepam.

Five and 11 days after withdrawal from 8 weeks of treatment with 90 mg/kg/day of diazepam p.o. or 60 mg/kg/day of lorazepam p.o. there were no consistent changes in the number of benzodiazepine receptors or apparent affinity $\text{in vitro}$ for ³H-diazepam at 0°C in rat forebrain membranes. Daily exposure of rats from 10 days before birth until 7 days after birth was also without gross effects on the benzodiazepine receptor. Abstinence and tolerance to benzodiazepines were thus not attributable to changes in brain benzodiazepine receptors.     

Withdrawal of long-term diuretic medication in elderly patients: a double blind randomised trial.

OBJECTIVES: About 20% of elderly people use long-term diuretic medication, but there is doubt whether prolonged diuretic medication on such a large scale is necessary. We performed a study to assess what proportion may successfully be withdrawn from diuretic therapy. DESIGN: Double blind randomised controlled trial with six month follow up. SETTING: General practice. SUBJECTS: 202 patients taking long-term diuretics without manifest heart failure or hypertension. INTERVENTIONS: Patients were allocated to either placebo (withdrawal group, n = 102) or continuation of diuretic treatment (control group, n = 100). MAIN OUTCOME MEASURE: Occurrence of clinical conditions requiring diuretic therapy based on fixed criteria. RESULTS: During follow up diuretic therapy was required in 50 patients in the withdrawal group and 13 in the control group (risk difference 36%; 95% confidence interval 22% to 50%). Heart failure was the most frequent cause of prescribing diuretic therapy (n = 25). Cessation of diuretic therapy caused a mean increase in systolic blood pressure of 13.5 (9.2 to 17.8) mm Hg and in diastolic pressure of 4.6 (1.9 to 7.3) mm Hg. CONCLUSION: Withdrawal of long-term diuretic treatment in elderly patients leads to symptoms of heart failure or increase in blood pressure to hypertensive values in most cases. Any attempt to withdraw diuretic therapy requires careful monitoring conditions, notably during the initial four weeks.     

Solubilization of benzodiazepine binding site from rat cortex.

The high-affinity binding site for [³H] diazepam has been solubilized from rat brain using 0.5% Lubrol-PX. Using a polyethylene glycol (PEG)-γ-globulin assay, it has been possible to demonstrate solubilization of about 60% of the binding sites in a single step. The solubilized binding site possesses a K_D of 11 nM for [³H] diazepam compared to approximately 4 nM for the membrane-bound form, and binding is to a single class of sites. The order of potency of benzodiazepines is identical for the solubilized receptor and the membrane-bound form. Binding of [³H] diazepam is temperature dependent and higher at 4° than 37°C. Both urea and guanidine-HC1 were capable of totally inhibiting binding, and this inhibition was partly reversible; neither sulfhydryl groups nor carbohydrate moieties seem to be important for binding. γ-Aminobutyric acid which enhanced [³H] diazepam binding to membrane fractions was without effect on the solubilized binding site.     

Withdrawal rates of DDT from chickens treated with diphenylhydantoin.

Male and female chickens of a broiler-type strain were fed, from 1 day old to 5 weeks of age, diets containing 0, 2.5, or 15.0 p.p.m. (mg/kg) 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT). Then the diets with pesticide were withdrawn and the chickens were fed dietary levels of diphenylhydantoin (DPH) at 0, 100, or 250 p.p.m. Adipose-tissue and liver samples were obtained on days 0, 10, 20, and 30 following withdrawal of diets with pesticides to determine DPH effect on DDT, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) levels. DPH had no effect on the concentration of DDT and DDE in adipose tissue; their levels declined at a rate having a half-life value of 16 days. DDD was not detected in adipose tissue. DDT accounted for 87% of the adipose residues on day 0, but 66% of the residues at day 30. DPH had no effect on the concentrations of DDT and DDE in livers of chickens fed 15.0 p.p.m. DDT, but did significantly reduce the levels of DDD by 28 and 54% for levels of 100 and 250 p.p.m. DPH, respectively. The similarity of these data to studies on dairy cows and humans, and the dissimilarity to data from rat studies were discussed.     

Withdrawal from chronic phencyclidine produces a pentylenetetrazol-like discriminative stimulus.

Rats trained to discriminate the anxiogenic compound pentylenetetrazol (PTZ) from water were implanted with osmotic mini-pumps containing 7 mg/kg/day phencyclidine (PCP) or water. Rats were tested for generalization to PTZ 24 hours prior to pump removal, and 4 to 96 hours after pump removal. While the pumps were in place, rats did not generalize to PTZ. When the pumps were removed on day 10, rats in the water group did not generalize to PTZ, but 69% of the rats in the chronic PCP group responded on the PTZ lever at 4 and/or 24 hours after pump removal, suggesting that the PCP withdrawal state mimics the interoceptive cue produced by PTZ. This withdrawal phenomenon was repeatable, in that rats that generalized once to PTZ during PCP withdrawal, generalized a second time when the procedure was repeated. In addition, the phenomenon was dose-dependent, as rats that did not generalize to PTZ after 7 mg/kg/day PCP did generalize when the chronic dose of PCP was increased to 10 mg/kg/day. These findings suggest that there is an anxiogenic component of PCP withdrawal and that tolerance does not develop to this effect.     

Decreased 3H-diazepam binding is a specific response to chronic benzodiazepine treatment.

Specific ³H-diazepam binding was measured in rat cortex after 7–10 days of twice daily treatment with large doses of either flurazepam or barbital. Subjective ratings of drug response each day showed that barbital treated rats experienced a degree of ataxia equal to, or greater than, that experienced by the benzodiazepine treated animals. Before performing the binding assay, the membrane preparation was washed 3 times in hypotonic buffer to remove aby residual drug. Flurazepam treatment caused a 16% decrease in maximal ³H-diazepam binding, but no change in binding affinity, confirming previous results. In contrast, barbital treatment caused no change in either binding affinity or in maximal binding. Thus, decreased diazepam binding appears to be a specific response to prolonged receptor occupation, and not part of a more generalized adaptation to chronic CNS depression.