Effects of nicotine and mecamylamine on rat dorsal raphe neurons

Eur J Pharmacol. 1998 Oct 30;360(1):31-6. doi: 10.1016/s0014-2999(98)00658-x.


This study investigates the hypothesis that serotonin mediates certain nicotine effects, such as mood improvement and the suppression of the ponto-geniculo-occipital spikes of rapid eye movement sleep. The influence of nicotine (10-300 microM) on the firing rate of dorsal raphe neurons and on serotonin release was therefore, studied in rat midbrain slices. Nicotine increased the firing rate, 10-90%, in 67.5% recorded neurons and decreased it, 8-100%, in the remaining 32.5%. Serotonin release increased 2-7 times after nicotine administration, regardless of firing frequency, but the absolute value of serotonin release was 3 times higher during the decreases than during the increases in firing rate. Mecamylamine (1-20 microM) transiently stimulated the dorsal raphe neurons and competitively antagonized the nicotine-induced serotonin release. The results support the working hypothesis and additionally show that mecamylamine also stimulates dorsal raphe neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Animals
  • Electrophysiology
  • Ganglionic Stimulants / pharmacology*
  • In Vitro Techniques
  • Male
  • Mecamylamine / pharmacology*
  • Neurons / drug effects*
  • Neurons / metabolism
  • Neurons / physiology
  • Nicotine / pharmacology*
  • Nicotinic Antagonists / pharmacology*
  • Raphe Nuclei / drug effects*
  • Raphe Nuclei / metabolism
  • Raphe Nuclei / physiology
  • Rats
  • Rats, Wistar
  • Serotonin / metabolism


  • Ganglionic Stimulants
  • Nicotinic Antagonists
  • Serotonin
  • Mecamylamine
  • Nicotine