Layer 1 calretinin thorn cells in monkey prefrontal cortex [poster presentation].
In: FENS Forum 2004 (4th Forum of European Neuroscience), 10-14 Jul 2004, Lisbon, Portugal, p. 244.
This immunocytochemical study examined the morphology of a remarkable type of highly thorned unipolar calretinin immunopositive non-pyramidal neuron in superficial layer 1 of medial prefrontal cortex (mPFC) in three juvenile macaque monkeys. Calretinin thorn cells had oval somata and possessed a single highly branched fan-like dendritic arbor which ramified parallel with the pia in layer 1. The immunolabelled dendrites possessed many characteristic spiny thorn-like processes. Labelled somata also gave rise to extensive varicose axonal arbors organised tangentially within layer 1. The morphology of calretinin thorn cells was different from Cajal-Retzius and other layer 1 neurons described previously.
Correlated light- and electron microscopy was used to ultrastructurally examine 45 axonal varicosities from identified calretinin thorn cells. These calretinin immunolabelled boutons established asymmetrical synapses with the shafts (32%) and spines (68%) of unlabelled layer 1 profiles. The dendrites of calretinin thorn cells were innervated by unlabelled symmetric and asymmetric synaptic junctions. The somata of calretinin thorn cells were infrequently innervated by calretinin immunopositive asymmetrical junctions.
These data provide evidence for the morphology and synaptic connectivity of a defined type of layer 1 calretinin neuron in PFC of juvenile monkeys - such cells may have strategic structural and functional roles in cortical development.
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