Changes in peripheral and central catecholaminergic and serotoninergic neurons of rats after acute and subacute administration of nicotine.

To establish dose-response relationships for nicotine (acute and subacute administration), we measured hemodynamic parameters as well as circulating and tissue catecholamines in sympathetically innervated organs in rats. We also investigated nicotines's influence on adrenoceptor binding sites of the heart and on serotonin metabolism. In conscious and anesthetized rats, we found a dose-dependent increase in circulating catecholamines after acute injection of nicotine. At low doses nicotine released norepinephrine, resulting in a decrease of blood flow and heart rate, whereas high doses of nicotine released epinephrine, resulting in a reversal of the cardiovascular parameters investigated. In the heart norepinephrine concentration increased after nicotine application. In the lung epinephrine rose markedly, whereas serotonin and 5-hydroxyindolacetic acid were diminished. After subacute administration of nicotine the number of binding sites for 3H-Dihydroalprenolol in the heart was significantly reduced, whereas norepinephrine content was increased. Dopamine, serotonin, and 5-hydroxyindolacetic acid were increased in the hypothalamus. Our findings show that nicotine not only affects peripheral and central catecholaminergic neurons, but also central serotoninergic neurons, thus enhancing turnover of these amines.