Effect of environmental enrichment on morphology of deep layer III and layer V pyramidal cells of occipital cortex in oldest-old rat – a quantitative Golgi Cox study [Utjecaj stimulativne okoline na morfologiju piramidnih neurona dubokih slojeva III i V okcipitalnog korteksa vrlo starih štakora: kvantitativna Golgi Cox studija]

Rašin, Mladen Roko and Darmopil, Sanja and Petanjek, Zdravko and Tomić-Mahečić, Tina and Mohammed, Abdul H. and Bogdanović, Nenad (2011) Effect of environmental enrichment on morphology of deep layer III and layer V pyramidal cells of occipital cortex in oldest-old rat – a quantitative Golgi Cox study [Utjecaj stimulativne okoline na morfologiju piramidnih neurona dubokih slojeva III i V okcipitalnog korteksa vrlo starih štakora: kvantitativna Golgi Cox studija]. Collegium Antropologicum, 35 (S. 1). pp. 253-258. ISSN 0350-6134

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Abstract

Dendrites and dendritic spine density regress extensively during aging in rats housed under standard conditions (SC), which can be ameliorated by housing in the enriched environment (EE). This event is particularly pronounced on neurons where high rates of plasticity are conceivable, such as on projection neurons of archicortical regions of dentate gyrus1. However, effects of EE on neocortical projection neurons are still poorly understood. Therefore, we investigated the effect of EE housing on a deep layer III (L3) and layer V pyramidal cell (L5) morphology in the associative occipital neocortex of male Sprague-Dawley rats at 24 months of age. Rats were randomly distributed in two groups and reared under either SC (n=5) or EE conditions (n=6) for 26 days. In depth quantitative analysis of dendritic tree morphology and spine density on occipital projection neurons, from Golgi-Cox stained sections, showed similar trend in both EE occipital layers L3 and L5. Significant increase was found in total number of dendritic segments (L3 – 37.5 %, L5 – 33 %) and in dendritic diameter of intermediate segments (for more than 20 %), while increase in total spine number was around the level of significance (p>0.55; L3 – 30 %, L5 – 64 %). These findings suggest an outgrowth of new dendritic segments. When compared to archicortical region of dentate gyrus, effects of aging in the associative occipital cortex were less pronounced. Taken together, these findings suggest that structures being more affected by the aging process are more susceptible to the environmental enrichment in old age.

Abstract in Croatian

Dendriti i gustoća dendritičkih trnova pokazuju značajne regresivne promjene tijekom starenja kod štakora koji borave u standardnim laboratorijskim uvijetima (engl. standard conditions, SC), a koje se mogu ublažiti boravkom u uvijetima stimulativne okoline (engl. enriched environment, EE). Taj efekat je osobito izražen na neuronima s velikim stupnjem plastičnosti kao što su projekcijski neuroni arhikortikalne regije gyrusa dentatusa. Međutim, utjecaj boravka u EE na projekcijske neurone u neokorteksu je još uvijek nedovoljno istražen. U ovoj studiji ispitali smo utjecaj boravka u stimulativnoj okolini na morfologiju piramidnih neurona dubokog sloja III (L3) i sloja V (L5) u asocijativnoom okcipitalnom neokorteksu muških Sprague-Dawley štakora starih 24 mjeseca. Štakori su nasumično raspoređeni u dvije grupe koje su boravile u SC (n=5) ili EE (n=6) kroz 26 dana. Detaljna kvantitativna analiza morfologije dendritičkog stabla i gustoće dendritičkih trnova na projekcijskim neuronima okcipitalnog korteksa prikazanih Golgi Cox metodom pokazala je sličan utjecaj boravka u EE u oba analizirana sloja – L3 i L5. Statistički značajan porast nađen je u ukupnom broju segmenata (L3 – 37,5%, L5 – 33%), te u promjeru dendrita na intermedijarnim segmentima (za više od 20%), dok je porast ukupnog broja dendritičkih trnova bio vrlo blizu statističke značajnosti (p>0,55; L3 – 30%, L5 – 64%). Ti podaci pokazuju da je najizraženiji efekat boravka u EE okolini bio izrastanje novih dendritičkih segmenata. S obzirom da je utjecaj starenja u okcipitalnom korteksu bio manje izražen nego u ontogenetski starijim moždanim strukturama kao sto je gryus dentatus, smatramo da strukture koje su jače zahvaćene staračkom regresijom plastičnije reagiraju na boravak u stimulativnoj okolini tijekom starenja.

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