Some Perspectives on the Effects of Nicotine on the Human Body

Lakes Laboratory, Northridge, California

Nicotine holds a unique fascination not only for smokers, but also for physiologists.Without nicotine, many fundamental research findings in the field of the autonomic nervous system might have been delayed by decades.If this substance had not been used by biologists as such an outstanding experimental tool, it is doubtful whether the extensive knowledge about nicotine itself would ever have become reality.Another motivation for studying nicotine’s effects is that nicotine is a potent component of tobacco use.Clearly, these two lines of inquiry are not separate; on the contrary, they are mutually beneficial.

But nicotine remains another challenge.Through its value as a physiological tool, a vast amount of information has been accumulated, including highly specialized data on electrical and neurohumoral events at the cellular and subcellular levels.The broad outlines of nicotine pharmacology have also been thoroughly investigated.It now falls to us to try to connect these two different bodies of findings.In other words, we must try to explain the various nicotine-related phenomena—such as autonomic, motor, and behavioral changes—in light of observations at the cellular level.

This presentation is divided into three parts.

The first is a brief survey of the peripheral pharmacology of nicotine, intended to establish some general concepts rather than to be exhaustive.

The second part attempts to synthesize current knowledge regarding the phenomenon of nicotine-induced knee-jerk inhibition.

Finally, a new study is presented concerning nicotine-induced hypotension and bradycardia in unanesthetized cats.

General pharmacological background

In the peripheral nervous system, including both autonomic and somatic nerves, there are various tissues that respond to nicotine.According to the available evidence, it can be said that most of these effects of nicotine mimic the actions of acetylcholine.The distinction proposed by Dale (1914) more than half a century ago between the “nicotinic” and “muscarinic” effects of acetylcholine has fully proven its usefulness in the peripheral nervous system, and it is now also of great significance for the central nervous system.