Elevated Blood Lead Concentrations in Essential Tremor: A Case–Control Study in Mersin, Turkey

Essential tremor (ET) is one of the most common neurologic disorders. Aside from underlying susceptibility genes, recent studies have also begun to focus on environmental toxic factors. Yet there remains a paucity of information on such factors, making studies of environmental factors important. A recent study in New York City found blood lead concentrations to be elevated in ET cases compared with matched controls. Chronic exposure to lead produces cerebellar damage, and this could predispose individuals to develop ET

Association between essential tremor and blood lead concentration

Lead is a ubiquitous toxicant that causes tremor and cerebellar damage. Essential tremor (ET) is a highly prevalent neurologic disease associated with cerebellar involvement. Although environmental toxicants may play a role in ET etiology and their identification is a critical step in disease prevention, these toxicants have received little attention. Our objective was to test the hypothesis that ET is associated with lead exposure. Therefore, blood lead (BPb) concentrations were measured and a lifetime occupational history was assessed in ET patients and in controls. We frequency matched 100 ET patients and 143 controls on age, sex, and ethnicity. BPb concentrations were analyzed using graphite furnace atomic absorption spectrophotometry. A lifetime occupational history was reviewed by an industrial hygienist. BPb concentrations were higher in ET patients than in controls (mean ± SD, 3.3 ± 2.4 and 2.6 ± 1.6 µg/dL, respectively; median, 2.7 and 2.3 µg/dL; p = 0.038). In a logistic regression model, BPb concentration was associated with diagnosis [control vs. ET patient, odds ratio (OR) per unit increase = 1.21; 95% confidence interval (CI), 1.05-1.39; p = 0.007]. BPb concentration was associated with diagnosis (OR per unit increase = 1.19; 95% CI, 1.03-1.37; p = 0.02) after adjusting for potential confounders. Prevalence of lifetime occupational lead exposure was similar in ET patients and controls. We report an association between BPb concentration and ET. Determining whether this association is due to increased exposure to lead or a difference in lead kinetics in ET patients requires further investigation

On the positive and negative affective responses to cocaine and their relation to drug self-administration in rats

RATIONALE: Acute cocaine administration produces an initial rewarding state followed by a dysphoric/anxiogenic “crash”. OBJECTIVE: To determine whether individual differences in the relative value of cocaine’s positive and negative effects would account for variations in subsequent drug self-administration. METHODS: The dual actions of cocaine were assessed using a conditioned place test (where animals formed preferences for environments paired with the immediate rewarding effects of 1.0 mg/kg i.v. cocaine or aversions of environments associated with the anxiogenic effects present 15 min post-injection) and a runway test (where animals developed approach-avoidance “retreat” behaviors about entering a goal-box associated with cocaine delivery). Ranked scores from these two tests were then correlated with each other and with the escalation in the operant responding of the same subjects observed over 10 days of 1- or 6-h/day access to i.v. (0.4 mg/inj) cocaine self-administration. RESULTS: a) larger place preferences were associated with faster runway start latencies (r(s)=−0.64), but not with retreat frequency or run times; b) larger place aversions predicted slower runway start times (r(s)=0.62) and increased run times (r(s)=0.65) and retreats (r(s)=0.62); c) response escalation was observed in both the 1-h and 6-h self-administration groups and was associated with increased CPPs (r(s)=0.58) but not CPAs, as well as with faster run times (r(s)=−0.60). CONCLUSIONS: Together, these data suggest that animals exhibiting a greater positive than negative response to acute (single daily injections of) cocaine are at the greatest risk for subsequent escalated cocaine self-administration, a presumed indicator of cocaine addiction