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

Cholinergic Innervation
Cholinergic neurons form extensive networks with each other and with
glutamatergic and GABAergic neurons. Cholinergic neurons also interconnect
with other neuromodulator systems, such as networks using dopamine,
norepinephrine, serotonin and histamine, to modulate sensory information relayed
by glutamate synapses. Neuroplasticity is essential to the continuous updating
these neural networks and some cholinergic axons are particularly plastic (Farris et
al., 1995). At both central and peripheral sites, cholinergic receptor activation
leads to cytoskeletal responses. Centrally, muscarinic acetylcholine receptors,
which utilize G-protein mechanisms, far out number nicotinic acetylcholine
receptors, which are ionotropic in nature. In the periphery, nicotinic acetylcholine
receptors predominate. Despite marked differences in receptor mechanisms, the
binding of acetylcholine to either muscarinic or nicotinic acetylcholine receptors
triggers cytoskeletal protein interactions with other cytoskeletal proteins at central
and peripheral sites (Woolf, 2006).
Cholinergic neurons comprise less than one percent of neurons in the
nervous system, yet they appear to be involved in the most intriguing and
enigmatic of neural functions, ranging from gross observable movement to
consciousness. Cholinergic systems orchestrate activity across groups of muscle
cells and in conjunction monoamines - dopamine, norepinephrine, serotonin and
histamine neuronal assemblies in cortical fields. The end result is a unified action,
either behavioral or cognitive, which because of inherent neuroplasticity can be
honed through the learning process to become purposeful action (Woolf &
Butcher, 2010).
With a few exceptions, cholinergic neurons assume a ventral or basal
location. This ventral or basal location is consistent with the motor and “cognitive
action” functions of cholinergic neurons. Mesopontine cholinergic neurons are
located in the laterodorsal tegmental nucleus and the pedunculopontine tegmental
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