Morfološka i kemijska obilježja kalretininskih neurona u neokorteksu primata [Morphological and chemical characteristics of calretinin neurons in the primate neocortex]

Džaja, Domagoj (2015) Morfološka i kemijska obilježja kalretininskih neurona u neokorteksu primata [Morphological and chemical characteristics of calretinin neurons in the primate neocortex]. PhD thesis, Sveučilište u Zagrebu.

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Abstract

In this study the proportion of calretinin neurons in medio-orbital (MO) area of rat as well as in area 14c of monkey and human has been studied using stereological approach. Qualitative analysis showed that calretinin neurons have features of non-pyramidal (GABA) neurons. Quantitative analysis showed a five-fold increase in the proportion of calretinin neurons between rat (2,5%) and monkey (12,5%). In human there is an additional increase and they represent 15% of total neuron pool. The highest proportion of calretinin neurons is observed in monkey and human layer I, where half of neurons are expressing calretinin. Intrestingly, changes in structure of layer I imply that in primates it has more complex neuronal structure since almost 7% of all cortical neurons are located there, whereas in rat this proportion is slightly above 2%. In other layers incrase in the proportion of calretinin neurons between rat and monkey appears concurrently. In contrary, between monkey and human number of calretinin neurons increases in layer II/III more then total number of neurons, whreas in layers V and VI this pattern is reversed. It seems that there is a layer specific patter for functional specialization of local circuitry during primate evolution. Data about decrease in total neuronal density (NeuN) through cortical layers show that increase in the proportion of calretinin neurons correlates with increased dendritic complexity of particular layer as well as with increase in synaptic number and intra-areal connectivity. So, the lowest density is observed in layers of human cortex dominated by corticocortical neurons (II/III) where proportion of calretinin neurons is much above average (22%). We hypothethised that such a pronounced increase in proportion of calretinin neurons is related with reorganization of local circuitries resulting in increase of processing capacity without linear increase in number of projection neurons.

Abstract in Croatian

U ovom istraživanju stereološkim metodama analiziran je udio kalretininskih neurona u medio-orbitalnom (MO) polju štakora, te polju 14c u majmuna i čovjeka. Kvalitativnom analizom potvrđeno je kako kalretininskih neuroni imaju obilježja ne-piramidnih (GABA) neurona. Kvantitativni podaci su pokazali peterostruko povećanje udjela kalretininskih neurona između štakora (2,5%) i majmuna (12,5%). Kod čovjeka se njihov udio još dodatno povećao te oni čine 15% od ukupne populacije kortikalnih neurona. Najveći udio kalretininskih neurona zabilježen je u sloju I kod majmuna i čovjeka, gdje više od polovice neurona izražava kalretinin. Zanimljivo je i kako promjene u strukturi sloja I ukazuju da on kod primata u cjelini ima daleko složeniju neuralnu strukturu jer sadrži gotovo 7% od ukupnog broja svih kortikalnih neurona, dok je kod štakora taj udio nešto iznad 2%. U ostalim slojevima podjednako je povećanje udjela kalretininskih neurona u ukupnoj populaciji neurona između štakora i majmuna. Nasuprot tome, od majmuna do čovjeka u slojevima II/III broj kalretininskih neurona raste brže od ukupnog broja neurona, dok je u slojevima V i VI obrnuto. To ukazuje kako od majmuna do čovjeka evolucija lokalnih neuralnih krugova uključuje funkcionalnu specijalizaciju specifičnu za sloj. Podaci o smanjenju ukupne gustoće neurona (NeuN) po pojedinim slojevima pokazuju kako povećanje udjela kalretininskih neurona korelira s usložnjavanjem dendritičke morfologije neurona određenog sloja te povećanjem broja sinapsi i intra-arealnih projekcija. Tako je najmanja gustoća neurona zabilježena kod čovjeka u slojevima gdje dominiraju kortiko-kortikalni neuroni (II/III) i gdje je udio kalretininskih neurona znatno iznad prosjeka (22%). Može se pretpostaviti da ovakvo dramatično povećanje udjela kalretininskih neurona mijenja strukturu lokalnih neuralnih krugova i omogućava povećanje kapaciteta procesuiranja bez linearnog povećanja broja projekcijskih neurona.

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