[Intrinsic cholinergic components in the cholinergic innervation of the auditory cortex in the cat (zone AI)]

Neuronally isolated auditory cortical slabs (zone Al) of cat were studied using histochemical AChE reaction 3 days and 1, 2, 3 weeks after isolation. Following structures were observed: cholinergic long-axon associative neurons responding to the cortex isolation by retrograde degeneration and AChE hyperreaction (Cajal-Retzius cells of layer I and neurons of layer VI whose axons travel to the subcortical layer of the associative fibres); cholinergic short-axon associative cells of layers II-VI, which retain normal structure and moderate AChE activity after isolation; their axon collaterals terminate on neighbouring neurons; short-axon neurons are more numerous in deeper layers of the cortex; on the whole they predominate over the long-axon associative neurons; cholinoceptive cells (pyramidal and stellate) were found with cholinergic terminals on the soma and proximal parts of the dendrites; these terminals were formed by associative cell axons. Cholinoceptive neurons occurred more frequently in deeper layers of the cortex.