Modification of serotonin neuron properties in mice lacking 5-HT1A receptors

Eur J Pharmacol. 2002 Jan 25;435(2-3):195-203. doi: 10.1016/s0014-2999(01)01607-7.


Using null mutant mice for the 5-HT1A receptor (5-HT1A-/-), extracellular electrophysiological recordings were first conducted to evaluate the impact of its genetic deletion on the firing rate of dorsal raphe 5-hydroxytryptamine (5-HT) neurons. Experiments were also done using brain slices to assess whether any compensation phenomenon had taken place in key receptors known to control 5-HT and norepinephrine release. The mean firing rate of 5-HT neurons was nearly doubled in 5-HT1A-/- mice, although 65% of the neurons were firing in their normal range. In preloaded brain slices, the 5-HT1D/B receptor agonist sumatriptan equally inhibited the electrically evoked release of [3H]5-HT in mesencephalic slices (containing the dorsal and median raphe) from wildtype and 5-HT1A-/- mice. The 5-HT1B receptor agonist CP 93129 (1,4-dihydro-3-(1,2,3,6-tetrahydro-4-pyridinyl)-5H-pyrrol (3, 2-b) pyridin-5-one) and the alpha2-adrenoceptor agonist UK14,304 (5-bromo-N-(4, 5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine) produced the same inhibitory effect in both groups of mice in hippocampus and frontal cortex slices. No difference was observed on the UK14,304-mediated inhibition of [3H]norepinephrine from preloaded slices of the two latter structures between the two groups of mice. In conclusion, the loss of control of the 5-HT1A autoreceptor in 5-HT1A-/- mice lead to a significant enhancement of 5-HT neuronal firing, but it did not alter 5-HT or norepinephrine release in any of the brain structures examined. In addition, it was not associated with changes in the function of 5-HT1D and 5-HT1B autoreceptors and of alpha2-adrenergic heteroreceptors on 5-HT neurons, nor of that of alpha2-adrenoceptors on norepinephrine terminals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autoreceptors / metabolism
  • Brimonidine Tartrate
  • Hippocampus / drug effects
  • Hippocampus / metabolism
  • In Vitro Techniques
  • Male
  • Mice
  • Neurons / drug effects
  • Neurons / metabolism*
  • Norepinephrine / metabolism
  • Pyridines / pharmacology
  • Pyrroles / pharmacology
  • Quinoxalines / pharmacology
  • Raphe Nuclei / drug effects
  • Raphe Nuclei / metabolism
  • Receptor, Serotonin, 5-HT1B
  • Receptor, Serotonin, 5-HT1D
  • Receptors, Adrenergic, alpha-2 / drug effects
  • Receptors, Adrenergic, alpha-2 / metabolism*
  • Receptors, Serotonin / deficiency
  • Receptors, Serotonin / drug effects
  • Receptors, Serotonin / genetics
  • Receptors, Serotonin / metabolism*
  • Receptors, Serotonin, 5-HT1
  • Serotonin / metabolism*
  • Serotonin Receptor Agonists / pharmacology
  • Sumatriptan / pharmacology
  • Tritium


  • Autoreceptors
  • Pyridines
  • Pyrroles
  • Quinoxalines
  • Receptor, Serotonin, 5-HT1B
  • Receptor, Serotonin, 5-HT1D
  • Receptors, Adrenergic, alpha-2
  • Receptors, Serotonin
  • Receptors, Serotonin, 5-HT1
  • Serotonin Receptor Agonists
  • Tritium
  • 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one
  • Serotonin
  • Brimonidine Tartrate
  • Sumatriptan
  • Norepinephrine