Impaired maze performance in aged rats is accompanied by increased density of NMDA, 5‐HT_1A, and α‐adrenoceptor binding in hippocampus

Abstract

ABSTRACT:Using quantitative receptor autoradiography, we assessed binding site densities and distribution patterns of glutamate, GABA A , acetylcholine (ACh), and monoamine receptors in the hippocampus of 32-month-old Fischer 344/Brown Norway rats. Prior to autoradiography, the rats were divided into two groups according to their retention performance in a water maze reference memory task, which was assessed 1 week after 8 days of daily maze training. The animals of the inferior group showed less long-term retention of the hidden-platform task but did not differ from superior rats in their navigation performance during place training and cued trials. The decreased retention performance in the group of inferior learners was primarily accompanied by increased a 1 -adrenoceptors in all hippocampal subregions under inspection (CA1-CA4 and dentate gyrus), while elevated a 2 -adrenoceptor binding was observed in the CA1 region and DG. Furthermore, inferior learners had higher NMDA binding in the CA2 and CA4 and increased 5-HT 1A binding sites in the CA2, CA3, and CA4 region. No significant differences between inferior and superior learners were evident with regard to AMPA, kainate, GABA A , muscarinergic M 1 , dopamine D 1 , and 5-HT 2 binding densities in any hippocampal region analyzed. These results show that increased NMDA, 5-HT 1A , and a-adrenoceptor binding in the hippocampus is associated with a decline in spatial memory. The increased receptor binding observed in the group of old rats with inferior maze performance might be the result of neural adaptation triggered by age-related changes in synaptic connectivity and/or synaptic activity. V V C 2006 Wiley-Liss, Inc.

Serotonin 5-HT1A receptor binding sites in the brain of the pigeon (Columba livia)

“…Future studies are clearly needed to clarify the exact boundaries of different areas in the hippocampal formation of the avian species. The low overall density of 5-HT 1A receptors in the avian hippocampus is in contrast to that in rats and other mammals (Topic et al, 2007;Pazos and Palacios, 1985;Zilles et al, 1985Zilles et al, , 2000Wree et al, 1987;Zilles, 1989;Kraemer et al, 1995;Aznavour et al, 2009). …”

“…Low levels, or no binding, were reported in the basal ganglia and cerebellum (Gozlan et al, 1983;Marcinkiewicz et al, 1984;Zilles et al, 1985Zilles et al, , 2000Hall et al, 1997;Vergé et al, 1986;Albert et al, 1990;Palacios et al, 1990;Pompeiano et al, 1992;Khawaja, 1995;Kia et al, 1996a,b;Farde et al, 1997;Raurich et al, 1999;Hume et al, 2001;Maeda et al, 2001;Geyer et al, 2005;Palchaudhuri and Flügge, 2005;Eickhoff et al, 2007;Topic et al, 2007). 5-HT 1A receptors play a role in executive functions, anxiety related behavior, learning and reinforcement, feeding behavior, and locomotor activity (Zilles et al, 2000;Yilmazer-Hanke et al, 2003;Müller et al, 2007;Sumiyoshi et al, 2007;Topic et al, 2007;Borg, 2008;Perez-Garcia and Meneses, 2009). …”

Sexual dimorphisms in swimming behavior, cerebral metabolic activity and adrenoceptors in adult zebrafish (Danio rerio)

“…Specifically, zebrafish lateral zone of dorsal telencephalon (Dl), considered a homologue to the mammalian [65] and avian [66] hippocampus, included higher densities of α 2 -ARs in the females, exhibiting comparable densities of α 2 adrenergic receptors to those of birds [67] and mammals [68]. In support, α-ARs densities in rat hippocampus were also associated with gender related differences [29].…”

Developmental effects of 3,4-methylenedioxymethamphetamine: a review

“…The 5-HT 1A receptor has been implicated in learning and memory and is a possible mechanism for learning and memory deficits in MDMA-treated animals (Meneses and Perez-Garcia, 2007). In particular, increases in the 5-HT 1A receptor were observed in older rats that had deficits in the MWM (Topic et al, 2007). At high doses, the 5-HT 1A receptor agonist 8-OH-DPAT leads to decreased performance in a passive avoidance task, whereas administration of 5-HT 1A receptor antagonists facilitated passive avoidance learning (for review, see Meneses and PerezGarcia, 2007).…”