Mammals, strychnine toxicity

The data shown in Table 2 illustrate the general paucity of comparative toxicity data within an isosteric series of chemicals. In this Table a variety of toxic end-points observed for benzene and naphthalene have been compared with those of their simple heterocyclic analogues, and it is clear that it is almost impossible to derive chemical structure-biological activity relationships from the published literature for even such a simple series of compounds. Even basic estimates of mammalian toxicity such as LD50 values cannot be accurately compared due either to the absence of relevant data or the noncomparability of those available. Thus in a field where there are little comparative data on the relative toxicity to mammals of pyrrole, thiophene and furan for example, it is difficult to relate chemical structure to biological activity in historical heterocyclic poisons such as strychnine (3) and hemlock [active agent coniine (4)]. 

An example of a stimulant that is also a toxicant is the pesticide strychnine. This alkaloid works by neutralizing glycine, an amino acid responsible for transmitting inhibitory nerve impulses to muscles. Without inhibition, the muscles contract but do not relax. Skeletal muscles become hyperexcited and contract continuously. Limbs become stiff and respiration stops. Animals poisoned with strychnine suffocate and die. This poison is toxic to fish, insects, mammals, and birds. 

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