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Immunocytochemical and electron microscopic methods were used to examine neurons in regio superior of rat hippocampus displaying cholecystokinin octapeptide-like immunoreactivity. Cholecystokinin-immunoreactive synaptic terminals and somata are found in all layers of regio superior but are most numerous in stratum pyramidale. The vast majority of terminals form symmetric synaptic contacts onto the somata and proximal dendrites of hippocampal pyramidal cells and onto smaller dendrites which may also arise from pyramidal cells. A very small number of cholecystokinin-immunoreactive terminals form synapses that appear asymmetric and contact dendritic shafts or spines. The somata of some pyramidal cells receive symmetric synapses from cholecystokinin-immunoreactive terminals that are joined by cytoplasmic bridges to form parts of pericellular baskets. These and adjacent pyramidal cell somata are also contacted by terminals that are not immunoreactive for cholecystokinin. No cholecystokinin-positive terminals contacted the initial segments of pyramidal cell axons. Cholecystokinin-immunoreactive cells are found in all layers of regio superior. Their somata receive a few symmetric synapses, most of which are formed by terminals not immunoreactive for cholecystokinin. Their dendrites receive a greater number of both symmetric and asymmetric contacts, some of which are immunoreactive for cholecystokinin. We conclude the following: The localization of cholecystokinin immunoreactivity in synaptic terminals contacting the somata and dendrites of hippocampal pyramidal cells is consistent with the suggestion that cholecystokinin acts as a neurotransmitter at these sites and at sites in other parts of the cerebral cortex. Results from the present and previous studies suggest that cholecystokinin-like immunoreactivity may co-exist with gamma-aminobutyrate in some non-pyramidal neurons of regio superior. Cholecystokinin-immunoreactive terminals arise mainly from non-pyramidal cells intrinsic to the hippocampus, one class of which appears to be a type of basket cell.
S H Hendry, and
E G Jones
July 1998,
Neuroscience letters,
S H Hendry, and
E G Jones
January 1988,
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S H Hendry, and
E G Jones
January 1996,
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S H Hendry, and
E G Jones
April 1987,
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S H Hendry, and
E G Jones
August 1988,
Neuroscience,
S H Hendry, and
E G Jones
December 1982,
Neuroscience letters,
S H Hendry, and
E G Jones
March 1989,
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S H Hendry, and
E G Jones
August 1984,
The Journal of comparative neurology,
S H Hendry, and
E G Jones
January 2003,
Neuroscience,
S H Hendry, and
E G Jones
August 1984,
Neuroscience letters,
