This chapter covers additional aliphatic and aromatic compounds that contain one or more nitrogen atoms in their structures and follows those discussed in Chapter 59.
Pyridine and its many modified structures are described because they serve as a backbone for many industrial compounds.
Several pesticides and herbicides, as well as their precursors, are included: the pyridinethiones, the substituted uracils herbicides: bromacil, lenacil, terbacil; the quaternary herbicides: paraquat, diquat, and difenzoquat; the
s
‐triazines: atrazine and propazine and other triazine herbicides, such as ametryn, prometryne, and simazine.
Simple nitrogen compounds such as azides, nitrosamines, and hydrazines are described because of important toxicological effects they can produce.
Finally, two important industrial solvents, dimethylacetamide and dimethylformamide are included because they have a long history of use and have been well studied in the occupational environment.
Adult male rats pressed a lever on a multiple fixed ratio-fixed interval (FR20-FI120 sec) schedule of food presentation, and after attaining a stable baseline subjects received an acute inhalation exposure to cyclohexane vapor (0 ppm, 500 ppm, 2000 ppm, or 7000 ppm) for 6 hr. During the operant session that began 30 min after termination of exposure, FR running rate for the 7000 ppm group decreased 11% relative to performance on the previous day. FR post-reinforcement pause duration and the rate and pattern of FT performance were unaffected. Cyclohexane exposures of 500 or 2000 ppm had no detectable effects. No enduring effects of cyclohexane occurred up to 2 weeks after exposure. An independent set of rats, trained under nominally identical conditions, received various doses (i.p.) of d-amphetamine (AMPH) or chlorpromazine (CPZ) at 1-2 week intervals. Effective doses of AMPH decreased FR running rate, decreased FR post-reinforcement pause duration and increased FI rate of response. AMPH also decreased the FI index of curvature, indicating a change from an accelerating rate during the FI to a more constant rate. Effective doses of CPZ decreased FR rate, increased FR pause duration, decreased FI rate, and decreased FI index of curvature. Thus, schedule-controlled operant procedures that were sensitive to the effects of psychoactive drugs were able to identify only a minor and transient effect of the highest concentration (7000 ppm) of cyclohexane vapor on operant performance.
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