Pyramidal neurones hippocampus

Pyramidal neurons are the principal long-projecting cells of the cerebral cortex and hippocampus. They are so named because of the characteristic large apical dendrite, giving them a pyramidal shape. 

Intracerebroventricular injection of kainic acid has been shown to result in a well-characterized pattern of neuronal cell damage. In the hippocampus, kainic acid causes a selective lesion of the CA3 pyramidal neurons, an area rich in KA1 and GluR6 receptors. The lesion does not compromise passing axons, which is why this type of (excitotoxic) lesion is often referred to as axon-sparing . Kainic acid injection into the hippocampus also leads to epileptiform discharges in cells normally innervated by the damaged pyramidal neurons. 

CA3 pyramidal neurons receive the mossy fiber input from the granule neurons of the dentate gyrus. This connection is part of the 3-cell circuit of the hippocampus that is believed to be involved in learning and memory. 

FIGURE 52-10 Summary of adrenal steroid effects on neurons of the hippocampus, illustrating their ability to protect and stabilize the population of the dentate granule neurons and to potentiate damage caused by excitatory amino-acid release upon pyramidal neurons. E, estrogen. (From [41], with permission.)... 

CYPIBI mRNA in male and female Rhesus monkey frontal cortex, hippocampus, thalamus, and amygdala CYPIBI protein colocalized with mRNA in female brains but restricted to hippocampal pyramidal neurons in male brains (Scallet et al., 2005). 

CYP2D6 mRNA and protein in human brain regions by RT-PCR, Northern blot, and Immunobiot, in situ hybridization and IHC shows constitutive CYP2D6 mRNA expression in neurons of cerebral cortex, Purkinje and granule cell layers of cerebellum, reticular neurons of midbrain and pyramidal neurons of C47, CA2, and CAS subfields of hippocampus. Protein found in cortex, cerebellum, midbrain, striatum, and thalamus of human brain. IHC shows CYP2D6 in dendrites of Purkinje and cortical neurons and neuronal soma (Chinta et al., 2002). 

CYP2E1 mRNA seen in neurons of the cerebral cortex, Purkinje and granule cells of cerebellum, granule cells of dentate gyrus, and pyramidal neurons of CA1, CA2, and CA3 subfields of hippocampus in rat and human brain by in situ hybridization ethanol-induced brain expression in rat (Upadhya et al., 2000). 

Chronic nicotine induces CYP2E1 expression in cortical pyramidal neurons and cerebellar Purkinje cells no change seen in temporal cortex, hippocampus, putamen, or thalamus of monkey brain (Joshi and Tyndale, 2005, 2006). 

Durand GM, Kovalchuk Y, Konnerth A (1996) Long-term potentiation and fimctional synapse induction in developing hippocampus. Nature 381 71-75 Eder M, Becker K, Rammes G, et al (2003) Distribution and properties of functional postsy-naptic kainate receptors on neocortical layer V pyramidal neurons. J Nemosci 23 6660-... 

Dodd J, Kelly JS The actions of cholecystokinin and related peptides on pyramidal neurones of the mammalian hippocampus. Brain Res 205 337-350, 1981... 

Fig. 5.3 CPLA2 immunoreactivity in field CA1 of the hippocampus. A section from a normal rat, showing light cPLA2 immunoreactivity in pyramidal neurons (arrows). B section from a rat that had been injected with kainate 3 days earlier, showing increased labeling of pyramidal neurons (arrows). C, D sections from rats that have been injected with kainate 2 weeks (C) and 11 weeks earlier (D), showing increased labeling in astrocytes (arrows). Abbreviation sp stratum pyrami-dale. Scale A = 200 /xm, B = 80 /xm, C,D = 100 /xm. Reproduced with kind permission from Sandhya et al., 1998, Brain Research 788 223-231, Elsevier...

Fig. 9.3 Apolipoprotein D-immunolabeled sections of field CA1 of the hippocampus from a normal rat (A), and rats injected with kainate one (B) or 3 (C, D) days previously. Very few isolated neurons (arrow) are labeled for apolipoprotein D in the normal hippocampus (A). In contrast, large numbers of neurons are labeled for apolipoprotein D in the kainate-injected animals (B-D, arrows). The labeled neurons have features of pyramidal neurons (D, arrows). Scale bar=160 //m (A-C), 40 fim (D). Reproduced with kind permission from Ong et al., 1997, Neuroscience 79 359-367. Elsevier.

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