Modifications of the sympathetic skin response in workers chronically exposed to lead

The long-term effects of low-level lead intoxication are not known. The sympathetic skin response (SSR) was evaluated in a group of 60 former workers of a primary lead smelter, located in Santo Amaro, BA, Brazil. The individuals participating in the study were submitted to a clinical-epidemiological evaluation including questions related to potential risk factors for intoxication, complaints related to peripheral nervous system (PNS) involvement, neurological clinical examination, and also to electromyography and nerve conduction studies and SSR evaluation. The sample consisted of 57 men and 3 women aged 34 to 69 years (mean ± SD: 46.8 ± 6.9). The neurophysiologic evaluation showed the presence of lumbosacral radiculopathy in one of the individuals (1.7 percent), axonal sensorimotor polyneuropathy in 2 (3.3 percent), and carpal tunnel syndrome in 6 (10 percent). SSR was abnormal or absent in 12 cases, representing 20 percent of the sample. More than half of the subjects (53.3 percent) reported a history of acute abdominal pain requiring hospitalization during the period of work at the plant. A history of acute palsy of radial and peroneal nerves was reported by about 16.7 and 8.3 percent of the individuals, respectively. Mean SSR amplitude did not differ significantly between patients presenting or not the various characteristics in the current neurological situation, except for diaphoresis. The results suggest that chronic lead intoxication induces PNS damage, particularly affecting unmyelinated small fibers. Further systematic study is needed to more precisely define the role of lead in inducing PNS injury.

Autonomic functions and audiovisual reaction time in heroin addicts.

Radial pulse rate, systolic BP (SBP), diastolic BP (DBP), initial GSR0), GSR after 5 minutes of relaxation (GSR5), auditory reaction time (ART) and visual reaction time, (VRT) were measured in 30 male heroin addicts and compared with 25 male control subjects of similar age group. In heroin addicts DBP was significantly low (71.73 mmHg +/- 7.42, P < 0.05); while SBP although being low (106.13 mmHG +/- 10.08) was not significant. However, radial pulse was significantly higher. GSR0 was significantly higher (P < 0.001) but GSR5 was not significantly higher in these addicts, suggesting less sympathetic activity. In a separate group of ten heroin addicts effect of change in posture from supine to erect on BP was studied. This did not produce any rise in SBP or DBP at 1 and 2 min, suggesting probably inhibition of baroreceptor reflex. Auditory reaction time (ART) and visual reaction time (VRT) were significantly prolonged (P < 0.001 for each) in addicts, indicating deterioration of processing capability of CNS, or poor sensory-motor performance, or both.

Effects of succinylcholine and related substances administered into the medial preoptic area on the local EEG, body temperature, heart rate, galvanic skin resistance and biogenic amines.

Succinylcholine (Sch) which is a cholinergic neuromuscular blocker has been known to occasionally lead to episodes of malignant hyperthermia in swine and humans. In order to find whether it produces any hyperthermic effects through action on medial preoptic area, experiments were carried on by administering intracerebrally the chemical into the medial preoptic area through an in-dwelling cannula-cum-electrode in the free moving rat. The changes in body temperature and the local EEG were studied. For comparison purpose, the effects of carbachol, atropine and phenylephrine were also studied. Further, in the curarized state of no muscular activity, the effect of SCh on the preoptic area was again tested and also the changes in the other autonomic parameters of heart rate and galvanic skin resistance (GSR) were studied. It was observed that SCh given into preoptic area caused a clear hyperthermic effect. The effect was countered by prior administration of atropine into the site. After SCh the local EEG changed into a high amplitude slow wave format. The heart rate was not altered but the GSR increased by two-fold. Carbachol caused a rise in body temperature, heart rate and also GSR. SCh also caused a reduction in noradrenaline content of the hypothalamus by 23% while no change in dopamine and serotonin occurred. Serotonin increased by 28% in the brainstem with no change in the other amines. Septum showed an increase of noradrenaline and dopamine contents by 40% and 25% respectively. Keeping in view the monoaminergic connections and thermoregulatory role of the preoptic area, one may postulate that SCh could inhibit the warm sensors and the controls of the dual sympathetic mechanism which normally leads to an increase of sudomotor activity and a decrease of vasomotor activity, the inhibition resulting in rise of body temperature.