Age-dependent effects of serotonin-1A receptor gene deletion in spatial learning abilities in mice

Brain Res Mol Brain Res. 2004 Nov 4;130(1-2):39-48. doi: 10.1016/j.molbrainres.2004.07.012.


The serotonin (5-hydroxytryptamine, 5-HT) receptor 1A is involved in many physiological functions, including the regulation of learning and memory by acting either as an autoreceptor located on 5-HT neurons (raphe nuclei) or as a heteroreceptor on non-5-HT neurons, mainly in the hippocampal formation. To investigate whether the effects of 5-HT via 5-HT1A receptors on learning are age-sensitive, we evaluated the performance of young-adult (3 months old) and aged (22 months old) 5-HT1A knockout (KO) mice and their homologous wild types (WT) in the hippocampal-dependent spatial reference memory version of the Morris water maze. We demonstrated that young-adult 5-HT1AKO mice exhibit an impairment in learning and retention of the spatial task, as compared to WT mice, without showing any sign of change in their sensori-motor and locomotor abilities or motivation. This genotype effect does not persist during aging. In fact, aged 5-HT1AKO mice seem to be slightly facilitated during the early stages of learning. These results are consistent with a possible prevalence of 5-HT1A raphe functions in learning and memory abilities of young-adult animals, since the effects of the mutation on mice performance (impairment) are opposite to those found after intra-raphe injection of 5-HT1A agonists (facilitation), and with data showing increased activity of 5-HT neurons in 5-HT1AKO mice. The reduced effect of the mutation in aged animals possibly reflects the lower efficacy of autoreceptors due to aging and/or a prevalence of hippocampal heteroreceptors.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aging / physiology*
  • Analysis of Variance
  • Animals
  • Learning / physiology*
  • Male
  • Maze Learning / physiology
  • Mice
  • Psychomotor Performance / physiology
  • Receptor, Serotonin, 5-HT1A / deficiency*
  • Receptor, Serotonin, 5-HT1A / genetics
  • Retention, Psychology / physiology
  • Spatial Behavior / physiology*
  • Time Factors


  • Receptor, Serotonin, 5-HT1A