Cellular neuroscienceReversible reduction in dendritic spines in CA1 of rat and ground squirrel subjected to hypothermia–normothermia in vivo: A three-dimensional electron microscope study
Section snippets
Ground squirrels
Adult ground squirrels, Spermophilus undulatus, of both sexes and 600–700 g in weight, were caught in Yakutiya (Siberia) and kept in individual cages in a cold vivarium under natural photoperiodicity. Food supplemented with sunflower seeds and carrots, and nesting material was provided ad libitum. In November, the animals were individually placed in wooden hibernation boxes (20×20×25 cm) and transferred to a dark room having a temperature of 1–3 °C. Food was not provided during hibernation.
Synapse density
Each synapse was identified primarily on the basis of prominent PSDs and synaptic vesicles clustered close to the apposition zone. Using a volume disector synaptic densities were expressed as number of synapses identified per 100 um3 to tissue as in (Harris 1994, Fiala et al 1998, Popov et al 2004). Fig. 2 shows synapse density for both rats and ground squirrels. There are no significant differences for either functional state of rats (normothermia: 329 synapses±38; Cooling: 327±8; Recovery:
Discussion
The data presented show clearly that significant morphological changes in dendritic spines occur in both a hibernating (ground squirrel) and non-hibernating mammal (rat), subjected to low temperature. Thin dendritic spines decrease as a percentage of the population measured and there is a concomitant increase in the percentages of both stubby spines and synapses directly on dendritic shafts. Recovery on warming is similar in both animals, with reversion to the spine proportions observed before
Acknowledgments
Supported by EU FPVI Promemoria Contract No. 512012 and to V.I.P. (RFBR grant 05-04-49635-a).
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