C would be the correct answer
Tilbury Fox described infectious impetigo in children and newborns in 1864. He drew specific emphasis to the vesicular type, which is currently common in maternity units. Almquist demonstrated in 1891 that the infecting organism was a staphylococcus. Matzenauer established the relationship between pemphigus neonatorum and impetigo contagiosa in 1900 by identifying the activating microorganism. Animal inoculation was often unsuccessful, but in 1911, Landsteiner and his colleagues generated pemphigoid lesions in chimps. With these several discoveries, the understanding of impetigo remained roughly the same until 1917. Surprisingly, throughout the fifty-three years following Fox's discovery, the disease received no special attention in any significant pandemic. However, as a questionnaire confirmed, this hitherto rare and sporadic illness abruptly altered its character and erupted in more or less violent outbreaks in 1917. Few maternity cases were excluded, and several physicians who had never seen impetigo as a nursery concern were overwhelmed by the influx of cases. Nurseries were handled like hospitals for infectious illnesses everywhere, but only to a limited extent. Many were completely closed, and others should have been.
Answer:
b. The rats press the lever least when cocaine is presented.
Explanation:
Reinforcement or reward refers to the physiological processes by which a given behavior, such as drug use, becomes habitual. This occurs when neurons release the neurotransmitter dopamine to the nucleus accumbens (NAc) after drug use.
In tobacco, nicotine is the main component triggering of the reinforcement. Once inside the brain, nicotine activates nicotinic receptors, which in turn contributes to the reinforcement mechanism. Following repeated exposure to nicotine, a neuroadaptation process is established for some (but not all) effects of nicotine. Increased brain nAChRs (acetylcoline receptors) are observed in response to desensitization of these nicotine-mediated receptors. This desensitization can play an important role in the development of tolerance and dependence.
The fact that nicotine is a weak reinforcer, means that maybe the rat already had an neuroadaptation with this drug, not feeling anything with this drug anymore, and thats why he would prefer other drug, like cocaine, pressing the lever of nicotine less often.
