The central effects of paraoxon on blood pressure of rabbits after intravenous administration or infusion via a vertebral artery

Non-cholinergic lethality following intravenous injection of carbamate insecticide in rabbits

This study was undertaken to investigate the possibility that non-cholinergic mechanism accounts for acute lethality of cholinesterase (ChE) inhibitor. Physostigmine and carbamate insecticides (2-s-butylphenyl methylcarbamate (BPMC); isoprocarb, 2-isopropylphenyl methylcarbamate (MIPC); and propoxur, 2-isopropoxyphenyl methylcarbamate (PHC)) were employed as ChE inhibitors. Rabbits intravenously given any of the ChE inhibitors showed typical signs of anti-ChE poisoning, a marked inhibition of systemic ChE activity, and an increase in RR interval on an ECG. Injection of physostigmine or PHC at a lethal dose produced a pressor response before cessation of spontaneous breathing. In contrast, injection of MIPC or BPMC primarily elicited a cardiovascular collapse, characterized by a rapid and progressive decrease in blood pressure and a decrease in QRS amplitude of ECG, before cessation of spontaneous breathing. The atropine pretreatment inhibited the pressor response, but not the depressor response and the QRS change. The pretreatment antagonized acute lethality of the ChE inhibitors except BPMC. It is suggested that the mode of lethality for intravenous ChE inhibitor could be determined by a balance between anti-ChE activity and some mechanism other than ChE inhibition. BPMC produced acute lethality through the latter mechanism rather than the former one.

[Brain changes in parathion poisoning: observations in 42 cases]

A total of 42 cases were examined neuropathologically to determine possible toxic changes occurring in the brain after parathion intoxication. Sporadic anoxic alterations were observed in 7% of 41 cases in which the cause of death was acute intoxication. Nearly all cases (93%), however, showed marked hyperemia, often coupled with small reactionsless, periventricular hemorrhages which occurred in 40% of the cases. In one third of the cases (33%) there was moderate swelling of the oligodendroglia. Whereas histological evidence of edema was found in nearly one third of the cases (30%), comparison of the brain weights in these subjects with those of a large comparative collective showed definite pathologic brain weights in only five cases (12%) with 95% confidence limits. It is true that in 18 cases (42%) the brain weight was above the normal value if the confidence limit is ignored. Pronounced anoxic alterations were observed in only one case in which the individual survived the acute intoxication for 4 weeks after initial respiratory arrest. Predominantly toxic changes, however, could not be detected in any of the cases examined. This negative morphologic finding does not agree with the physiologic alterations reported by other investigators using animal models; they considered the cause of death in cases of parathion intoxication to be the result of toxic paralysis of the respiratory center. The literature was discussed.