Lester D. Grant

Brainstem catecholamine neurons are target sites for sex steroid hormones

Sex steroid hormones and catecholamines have physiological interactions in the brain. By the combined use of autoradiography and fluorescence histochemistry, steroid hormone target sites and catecholamine neurons were visualized simultaneously in the same tissue preparation. By this dual localization method, [3H]estradiol and [3H]dihydrotestosterone target sites were identified in nuclei of many catecholamine cell bodies in the brainstem, and catecholamine nerve terminals were observed near certain steroid hormone target neurons. These results suggest close anatomical interrelations between steroid hormone sites of action and catecholamine sites of production and action in the brain.

Chronic low-level lead toxicity in the rat. III. An integrated assessment of long-term toxicity with special reference to the kidney.

Abstract Male and female rats whose mothers had been exposed to Pb before and during pregnancy and lactation at exposure levels of 0, 0.5, 5, 25, 50, and 250 ppm Pb as Pb-acetate in drinking water were continued on the respective regimens for 6 or 9 months. Body weights of males and females were not significantly different from controls at 6 months of age; however, female body weights were significantly decreased at 250 ppm at 9 months of age. In males at 9 months of age, spleen weights were significantly increased at 250 ppm Pb and kidney weights were increased at 0.5 ppm Pb and above; in females the liver, pituitary, and heart weights were affected at 250 ppm Pb. No significant Pb effects were found in sperm counts or sperm morphology, hematology profiles, or serum chemistries. Blood, brain, femur, and kidney Pb levels as well as urinary ALA excretion were all significantly dose related. Histopathological lesions were noted in the spleen (250 ppm) and in the kidney as evidenced by cytomegaly/karyomegaly (beginning at 5 ppm in males; 25 ppm in females), nuclear inclusion body formation and increased numbers of iron-positive granules within renal proximal tubule cells. These effects were more marked after 9 months exposure. Ultrastructural studies revealed mitochondrial swelling and the presence of increased numbers of lysosomes within renal proximal tubule cells. Energy-dispersive X-ray microanalysis, performed on adjacent sections, showed the highest intracellular Pb concentrations in nuclear inclusion bodies within renal proximal tubule cells. Inhibition of renal mitochondrial respiration for both succinate and NAD-linked substrates was found in 50- and 250-ppm Pb exposure groups at 9 months but not at 6 months. Mitochondrial δ-aminolevulinic acid synthetase and ferrochelatase, but not δ-aminolevulinic dehydratase, were also found to be inhibited at these Pb levels at 9 months. The lowest exposure level resulting in a detectable effect of Pb (cytomegaly/karyomegaly in renal proximal tubule cells) was 5 ppm associated with a median blood Pb concentration of 11 μg/dl.

Chronic low-level lead toxicity in the rat: II. Effects on postnatal physical and behavioral development

Abstract This report is the second in a series dealing with the chronic exposure of rats to lead (Pb) in drinking water. Weanling female CD rats were provided semipurified diets and deionized water containing 0, 0.5, 5, 25, 50, or 250 ppm Pb (as lead acetate). Following exposure for 6–7 weeks, females were mated with unexposed males and exposure continued throughout pregnancy and lactation. At 21 days of age, offspring were weaned onto the same concentration their mothers had been given, and exposure continued until sacrifice at 6 or 9 months of age. Significant depressions in body weight were seen at most time points for offspring exposed to 50 and 250 ppm Pb. Clinical signs of respiratory infection, as well as poor fur condition, tail-tip necrosis, and sialodacryoadenitis were noted to occur at 250 ppm. Highly significant delays in age at vaginal opening were noted in 25-, 50-, and 250-ppm females. Surface righting and air righting were delayed in 50- and 250-ppm animals. Locomotor development was unaffected except for an increase in pivoting in 250-ppm animals at Day 14 of age. Postweaning activity levels were unaltered when measured in either the open field or the circular photocell activity cage and evaluations of motor coordination using the rotorod test showed no effects of Pb. Food and water consumption based on body weight were essentially unchanged. Overall, the “lowest effect level” for Pb using chronic oral exposure was 25 ppm, a level associated with alterations in reproductive development. In other reports from this study, immune function and performance of an operant task in adults were altered at 25 ppm (blood Pb, 20–40 μg/dl), and renal morphology after 9 months of exposure was altered at 5 ppm (blood Pb, 10–16 μg/dl). The importance of reporting blood and tissue Pb concentrations for comparing Pb dose-effect among studies is emphasized.

Alterations in consummatory behavior following intracisternal injection of 6-hydroxydopamine.

Abstract Intracisternal administration of two doses of 6-hydroxydopamine, one with pargyline pretreatment and one without, caused an initial disruption of consummatory behavior. In spite of measures to enhance recovery from these acute effects, 6-hydroxydopamine treated rats were found to maintain body weight at a lower level than control rats. Similar to controls, treated animals were found to drink water in the absence of food and to enhance water consumption in response to the administration of a hypertonic saline solution. However, unlike control rats, animals treated with 6-hydroxydopamine failed to increase food intake following insulin administration. Desoxycorticosterone acetate (DOCA) treatment enhanced saline preference in 6-hydroxydopamine treated rats, but the maximum volume of saline consumed was markedly less than the intake of control rats following DOCA treatment. While control rats drank a large volume of either a sucrose or a saline solution when substituted for water, 6-hydroxydopamine treated animals showed little increase in their intake of these solutions. Preferential deplition of norepinephine in brain did not alter consumption of a sucrose solution; however, depletion of dopamine produced a significant reduction in sucrose intake. These latter findings suggest that this deficit observed in the 6-hydroxydopamine treated rat involves interruption of dopaminergic pathways.

Behavioral effects of moderate lead exposure in children and animal models: Part 1, clinical studies

(1980). Behavioral effects of moderate lead exposure in children and animal models: Part 1, clinical studies. CRC Critical Reviews in Toxicology: Vol. 8, No. 1, pp. 43-99.

Chronic low-level lead toxicity in the rat: I. Maternal toxicity and perinatal effects☆☆☆

Abstract The first in a series of studies on the chronic exposure of rats to lead (Pb) is reported here. Weanling females were provided semipurified diets containing no detectable Pb, and drinking water containing 0, 0.5, 5, 25, 50, or 250 ppm Pb (as Pb-acetate). Rats were exposed to Pb-acetate for 6–7 weeks, then mated and exposed continuously throughout gestation and lactation. No statistically significant change in food or water consumption was noted in any exposure group. Females in the 50- and 250-ppm groups exhibited significant growth retardation within 1 to 3 weeks after exposure began. In addition, vaginal opening was significantly delayed in the 50- and 250-ppm groups, and to a lesser extent in the 25-ppm group. The level of Pb exposure used here did not affect the ability to conceive, to carry a normal litter to term, or to deliver the young. The percentage of malformed fetuses, resorptions, and postpartum pup deaths to weaning were unaffected by Pb exposure. Body lengths of female offspring in the 250-ppm exposure group were significantly shorter than those of controls, and there was a tendency for all young in this group to be smaller. The estimated dose of Pb consumed (mg/kg) indicated that groups were exposed to different amounts of Pb, and tissue (blood, brain, and bone) Pb concentrations indicated dose-related patterns. Urinary aminolevulinic acid concentrations were significantly dose related and were significantly correlated with blood Pb concentrations. Maternal toxicity occurred in groups exposed to 25 ppm Pb or higher and was associated with a minimum blood Pb concentration of 20 μg/dl.

Alteration of avoidance and ingestive behavior after destruction of central catecholamine pathways with 6-hydroxydopamine

Abstract Alterations of shuttle-box avoidance acquisition, ingestive behavior, and catecholamine content in 4 different parts of brain were determined following bilateral infusion of 6-hydroxydopamine into the ventral tegmental area containing A-10 dopamine cell bodies, the tegmental segment of the ascending norepinephrine pathways, the globus pallidum, or the caudate-putamen. The maximum antagonism of active avoidance acquisition occurred following placement of 6-hydroxydopamine into the ventral tegmental and caudate areas. No effect on either avoidance or ingestive behavioral measures occurred after infusion of 6-hydroxydopamine into the norepinephrine pathways. Factor analysis of behavioral and biochemical data suggested that only striatal dopamine content bore a high relationship to avoidance behavior, while ingestive behavioral measures were highly related to both striatal and limbic dopamine content. Results suggest a functional—anatomical differentiation of dopamine pathways in brain.

Biochemical and behavioural alterations following 5,6-dihydroxytryptamine administration into brain

Abstract Administration of 75 μg 5,6-dihydroxytryptamine (5,6-DHT) intracisternally caused a prolonged reduction of brain serotonin with little effect on brain catecholamines. This effect was moderately potentiated by administering an additional dose of 5,6-DHT or pretreating animals with pargyline before injection of 5,6-DHT. Injections of 5,6-DHT into the raphe nuclei also caused reductions in brain serotonin, but caused severe tissue damage in some rats as well. 5,6-dihydroxy-tryptamine (40 μg) given intracisternally to 7-day-old neonatal rats produced only a 30% reduction of serotonin. Reduction of tryptophan hydroxylase activity following 5,6-DHT treatment supports the view that the depletion of brain serotonin may be the result of fibre degeneration. In spite of moderate effects of 5,6-DHT on brain serotonin, treatments caused behavioural alterations including enhanced muricide and facilitated acquisition of an active avoidance task.

Effect of central catecholamine alterations by 6-hydroxydopamine on shuttle box avoidance acquistion

Abstract Rats treated intracisternally with multiple doses of 6-hydroxydopamine (2 × 200 μg) in combination with pargyline, which depleted both brain norepinephrine and dopamine, showed no evidence of acquisition of an avoidance response in the shuttle box. Mean intertrial interval (ITI) crosses were not significantly different from control. Treatment with 2 × 250 μg of 6-hydroxydopamine without pargyline also retarded acquisition of avoidance, but to a lesser extent. ITI crosses for this latter group were significantly increased. Preferential depletion of norepinephrine facilitated acquistion of avoidance and increased the number of ITI crosses. The rate of acquisiton of the avoidance response by rats in which dopamine was preferentially reduced was not significantly different from control animals even though ITI crossing was significantly increased. These results are discussed in relation to views concerning the role of brain catecholamines in avoidance responding.

Lead poisoning and reproduction: effects on pituitary and serum gonadotropins in neonatal rats.

Abstract In order to investigate the effects of neonatal lead poisoning on pituitary gonadotropic function, newborn rats were given daily doses of lead (25, 100, and 200 mg/kg) by gastric gavage. Control rats were given deionized water. Groups of animals were sacrificed at 10, 15, and 20 days of age and serum and pituitary levels of the gonadotropins follicle stimulating hormone (FSH) as well as pituitary contents of luteninizing hormone (LH) were determined by radioimmunoassay. Lead concentrations in blood, bone, brain, and pituitary tissues of similarly treated 15-day-old rats were determined by atomic absorption spectrometry. Lead content in bone (femur) and brain showed dose-dependent elevations throughout the dose range; in blood, it reached a plateau of about 1000 μg% already at the dose of 100 mg/kg/day. Lead remained at undetectable levels (