Muscarinic M1, M3, Nicotinic,GABAA and GABAB Receptor ...

α7 NICOTINIC ACETYLCHOLINE RECEPTOR GENE EXPRESSION IN
BRAIN REGIONS OF EXPERIMENTAL RATS
In the brain, nicotinic receptors include several subtypes with differing
properties and functions. The abundant presence of α7 nAChR’s in the
hippocampus, neocortex and basal ganglia (Clarke et al., 1985), in conjunction
with the memory-enhancing activity of selective α7 nicotinic agonists such as
DMXB (Bitner et al., 2007), suggests a significant role for α7 nAChR’s in
learning and memory.
Present study on analysis of α7 nAChR expression levels in different brain
regions of hypoglycemic and diabetic rats showed that glucose deprivation
significantly affects its expression thereby contributing to functional deficits. Our
results showed an increased expression of α7 nAChR in cerebral cortex,
cerebellum, brain stem, corpus striatum and decreased expression in hippocampus
of hypoglycemic rats compared to diabetic and control rats. A previous study
demonstrated a critical involvement of α7 nAChRs in hippocampal gamma band
oscillations (Song et al., 2005). Confocal studies using specific antibody for α7
nAChR confirmed the mRNA expression in cerebral cortex, cerebellum, brain
stem, corpus striatum and hippocampus in experimental rats which showed
significant alterations in hypoglycemic condition. Similar to the hippocampus,
functional α7 nAChRs are present on GABAergic interneurons in the human
cortex (Alkondon et al., 2000) and the majority of parvalbumin-positive cells in
the human cortex express α7 nAChRs (Krenz et al., 2001) inviting the possibility
that α7 nAChRs can directly modulate cortical GABAergic neurotransmission and
gamma band oscillations, deficits of which underlie the cognitive deficits seen in
schizophrenic patients. α7 nAChR activation is involved in performance on a
variety of cognitive tests related to working, short-term, and longterm memory
function in animal models (Boess et al., 2007; Pichat et al., 2007; Hashimoto et
al., 2008). Because the nAChR admits Ca 2+ into the neuron (Vijayaraghavan et
119