Age-dependent effects of serotonin-1A receptor gene deletion in spatial learning abilities in mice.
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.
Wolff
Mathieu
M
Laboratoire de Neurosciences Cognitives, CNRS UMR 5106, Université de Bordeaux 1, Avenue des Facultés, 33405 Talence cedex, France.
Costet
Pierre
P
Gross
Cornelius
C
Hen
René
R
Segu
Louis
L
Buhot
Marie-Christine
MC
D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D007858:Learning / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D011597:Psychomotor Performance / Q000502:physiology; D044282:Receptor, Serotonin, 5-HT1A / Q000172:deficiency* / Q000235:genetics; D012153:Retention, Psychology / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology*; D013997:Time Factors
D044282:Receptor, Serotonin, 5-HT1A