Chronic Effects of Mercury on Organisms:

The effect of mercury on conditioned reflex activity


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THE EFFECT OF MERCURY ON CONDITIONED REFLEX ACTIVITY Summary only Our results correspond with those of A. Swensson (1959) who showed that organomercurials were retained longer in the brain than in other organs. The accumulation of mercury in brain tissue corresponds with definite morphological changes in it which will be discussed in one of the following chapters. As a rule, these changes are characterized by mildly pronounced hemodynamic and dystrophic changes. We and V. N. Kurnasov (1962) observed lightening and vacuolization in the pyramidal cells of the cortex. These and other morphological changes appeared in most animals during prolonged mercury exposure without cell destruction. In animals affected by ehtylmercury compounds, the higher concentrations produced more pronounced changes such as noticeable dystrophy, sometimes non-reversible (sclerosis of neural elements, karyoctosis) and marked hemo-dynamic disorders. In conclusion, we will review the facts proceeding from the data herein discussed. First - there is progressive alteration in conditioned reflex activity under exposure to mercury at or slightly less than 0.01 mg/m3. The data obtained in cats agrees with analogous observations of M. M. Gimadeyev (1958) in rabbits and V. N. Kurnosov (1962) in white rats. In the latter case, the disruption of higher nervous activity in test animals arose in a longer experiment (to 9.5 months) at an aerial mercury concentration of 0.002 - 0.005 mg/m3, that is, 2 - 5 times lower than the maximum permissible concentration for industrial sites. It is very significant that at such insignificant levels mercury is detectable in brain tissue in "increased" amounts according to V. N. Kurnosov, (from 0.006 - 0.02 mg/100g tissue). The second item is that changes in higher nervous activity produced by chemicals varying in action mechanism on cranial processes, can be normalized by restoration of the active SH- group content. This recalls the reversible nature of conditional reflex activity caused by SH- group blockage and the significance to normal cortical processes of biochemical transformations in which thiol compounds participate.