Cholinergic Neuromodulation II

ME.6200

Cholinergic Neuromodulation II

Prof. Gregor Rainer

LC; locus ceruleus (NE)

ldt, laterodorsal tegmental nucleus

LH, lateral hypothalamus

ms, medial septal nucleus

ppt, pedunculopontine nucleus

si, substantia innominata

SN, substantia nigra

vdb, vertical diagonal band nucleus

bas, nucleus basalis

BLA, basolateral amygdala

DR, dorsal raphe (5-HT)

EC, entorhinal cortex

hdb, horizontal diagonal band nucleus

Icj, islands of Cajella

IPN, interpeduncular nucleus

Cholinergic CNS projections

Cholinergic CNS effects: Septo-Hippocampal pathway



DR, dorsal raphe





LC; locus ceruleus








The hippocampal theta (4-8Hz) rhythm

LIA

LIA: Large irregular activity

The hippocampal theta (4-8Hz) rhythm

The hippocampal theta rhythm in rat is probably the most well-studied biological rhythms. We

distinguish type I (non-cholinergic, movement-related) and type II (cholinergic, not movement-

related) theta. Type I theta has higher peak frequency and greater amplitude than type II theta.

Type I theta is observed during exploratory behavior associated with voluntary movements such as

walking, hopping, head movements and manipulatory paw movements.

Type II theta is observed during periods of alert immobility, during the delivery of sensory stimuli in

the auditory, visual and somatosensory modality.

Outside of theta, the hippocampus shows LIA (large irregular activity) that does not have a clear

theta peak, and is associated with automated behaviors such as grooming. LIA often includes

«sharp waves», large amplitude broad band frequency events.

Infusion of Carbachol into the medial

septum (MS) region produces robust

theta activity, during behavioral

states not or weakly associated with

theta oscillatory activity.

Behaviorally, Carbachol application

in the MS elicits exploratory behavior

including walking, sniffing, rearing

followed later by an extended period

of alert immobility.

Infusion Atropine reduces type II

theta rhythm and associated

behaviors, while not affecting type I

theta.

Exploratory behavior

Automated motor behavior

Alert immobility

In vivo behavioral pharmacology of the theta rhythm

Type I theta is not cholinergically controlled

• The two types of Hippocampal theta rhythm are associated with

exploratory behavior and alert immobility respectively. Type II theta

has a lower peak frequency and is controlled by the Cholinergic

system.

• Delivering Carbachol to the medial septum induces theta in the

hippocampus and elicits theta-associated behaviors.

Take Home Message

Two components of Acetylcholine response to exploration of novel environment

Neuroscience. 2001;106(1):43-53. http://dx.doi.org/10.1016/S0306-4522(01)00266-4

o Control animals (kept in home cage, no exploration)

I Expl

II Expl

Exploration of novel environment: strong enhancement in Ach, not

correlated with motor exploration. >> Other mechansims (type I theta)

control behavior here.

Exploration of familiar environment:weaker enhancement in Ach,

correlated with motor exploration. >> type II theta regime.

The Journal of Physiology, 562, 81-88. January 1, 2005

In vitro activation of CA3 pyramidal cell by medial septum stimulation

Electrical microstimulation in the presence of AMPA/kainate,

NMDA, GABAA and GABAB receptor antagonists in the slice

medium.

50 ms

100 μ

V

Induction of fast oscillations in field CA3 of hippocampal slices by Carbachol (CCh)

PNAS March 4, 2003 vol. 100 no. 5 2872-2877

Note: CCh is a mAChR agonist that does not cross the

BBB. It activates both nAChR and mAChRs.

Nature Neuroscience 4, 1259 - 1264 (2001)

Human hippocampal-rhinal cortex gamma range (32−48 Hz) oscillatory synchronization

predicts subsequent memory

doi:10.1038/nn759

PNAS February 8, 2005 vol. 102 no. 6 2158-2161

ACh lesion Control

delay lengths [s] list lengths [N. items]

Rhinal cortex cholinergic deafferentation produces severe memory impairment

AChE staining

http://dx.doi.org/10.1073/pnas.0409708102

Local infusion of cholinergic immunotoxin

severly disrupts memory in a delayed-non-

matching-to-sample task. Effects are

similar in magnitude to complete ablation of

this cortex.

Rhinal cortex is essential for storing the

representations of new visual stimuli,

thereby enabling their later recognition.

ACh

Current theory of rhinal cortex

function as „gatekeeper for

declarative memory“

The more familiar an item is, the

less rhinal processing it requires

and the less vigorously it is

encoded into memory.

Rhinal cortex cholinergic deafferentation produces severe memory impairment

http://dx.doi.org/10.1016/j.tics.2006.06.003 Trends in Cognitive Sciences Volume 10, Issue 8, August 2006, Pages 358-362

http://www.sciencedirect.com/science/journal/13646613

http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=

Muscarinic prefrontal or temporal cortex blockade impairs object/place task performance

Learn. Mem. 2009. 16: 8-11 http://dx.doi.org/10.1101/lm.1121309

Bilateral Muscarinic blockade

(scopolamine) in rhinal or the

prefrontal cortex impairs object/place

test performance.

This test does not involve any specific

training, but relies on the innate

tendency of animals to explore novel

objects or places more than familiar

ones.

Unilateral Scopalamine infusion in

rhinal cortex together with prefrontal

cortex of the opposite hemisphere has

the same effecs as bilateral infusions

in each structure.

Object-in-place associative memory

depends upon cholinergic modulation

of neurones within the PRH-PFC

circuit

• The two types of Hippocampal theta rhythm are associated with

exploratory behavior and alert immobility respectively. Type II theta

has a lower peak frequency and is controlled by the Cholinergic

system.

• Delivering Carbachol to the medial septum induces theta in the

hippocampus and elicits theta-associated behaviors.

• In vitro work has shown that cholinergic agonists can also induce

higher frequency oscillations (including gamma oscillations).

• Synchronization of oscillations between hippocampus and rhinal

cortex predicts memory encoding.

• Impaired oscillatory interaction between hippocampus and

adjacent cortex may underlie amnesia and learning impairments.

Take Home Message



DR, dorsal raphe





LC; locus ceruleus








Cholinergic CNS effects: Visual System

Neuroscience 132 (2005) 501–510

Acetylcholine is increased in visual cortex during visual stimulation


Prefrontal Visual

Visual Visual

Blue: Visual projection

Yellow: Prefrontal projection

Red: ChAT

• Acetylcholine release in the cortex is regionally specific. Increases are

observed in the visual cortex, but not in the prefrontal cortex, during visual

stimulation. Basal forebrain cholinergic projections to the visual system

originate mainly in the NBM/HDB region.

Take Home Message

Orientation selectivity in primary visual cortex (V1)

Neuron Volume 56, Issue 4, 21 November 2007, Pages 701-713

NIC: nicotine

MEC: mecamylamine (an nAChR antagonist)

Nicotine enhances visual response gain of layer 4 visual cortex neurons

nAChRs are expressed presynaptically at thalamic

synapses onto excitatory, but not inhibitory, neurons

in the primary thalamorecipient layer 4c.

Psychophysical effect of Nicotine on grating detection in humans

with Nicotine

Response threshold

Nicotine boosts neural signals at low contrast

0 .1 .5 1 0

20

40

60

Contrast Level

Sp

ike R

ate

[H

z]

V1 Neuron contrast response function

nAChR Agonist

Recovery

Control

Rmaxcontrol

RmaxnAChR

C50control

C50nAChR

C50…. Semi-saturation contrast

Rmax…. Responsivity

Naka-Rushton function

Drifting sinusoidal gratings were presented at 3 different contrast levels (0.1, 0.5, 1) and at 8 different directions with and without iontophoretic cholinergic drug application.

Nicotine enhances contrast response in tree shrew V1

Bhattacharyya et al Eur J Neurosci 35(8): 1270-1280 (2012)

Rmax but not C50 affected by cholinergic agonists

0 20 40 60 80 100 0

20

40

60

80

100

Control R max

[Hz]

Dru

g R

max [H

z]

0 0.2 0.4 0.6 0.8 1 0

0.2

0.4

0.6

0.8

1

Control C 50

Dru

g C

50

nAChR

mAChR nAChR

mAChR

200 400 600 800 1000 1200 1400

-100

0

100

200

300

nAChR Agonist

D C

RF

A [H

z]

Depth [ m m]

200 400 600 800 1000 1200 1400

-100

0

100

200

300

mAChR Agonist D

CR

FA

[H

z]

Depth [ m m]

Supragranular Granular Infragranular 0

20

40

60

D C

RF

A [H

z]

mAChR Agonist

nAChR Agonist

Laminar differences in nicotinic and muscarinic modulation

P<0.05

Nicotine enhances thalamocortical activation

cortex

LGN

thalamus

fro

m r

etin

a

nAChR

mAChR

Glutamatergic

GABAergic

Cholinergic

Muscarinic stimulation mostly affects non-granular layers

Diffusion Tensor Imaging of

the BF to V1 projection

Courtesy Dr. David Leopold, NIH, Bethesda (USA)

Basal forebrain (BF) projections to primary visual cortex (V1)

Experimental Setup

BF stimulation elicits -band oscillations and reduces D-band activity

Peaked and broad -band spectral changes following BF stimulation

DOI: 10.1111/j.1460-9568.2010.07171.x

in vitro rat visual cortex

kainate / carbachol application

BF DBS increases responsivity and contrast sensitivity in V1: example

MUA site

BF DDBS

BF DBS

CONTROL

C50control

C50bf dbs

Rmaxcontrol

Rmaxbf dbs

C50…. Semi-saturation contrast

Rmax…. Responsivity

Naka-Rushton function

Drifting sinusoidal gratings were presented at 3 different contrast levels (0.1, 0.5, 1) and at 8 different directions with and without BF stimulation.

BF DBS increases responsivity and contrast sensitivity in V1:

population

Rmax and C50 changes in previous Literature

Study Manipulation Area Rmax C50

Bhattacharyya et al 2012 nAChR, mAChR activation V1 =

Soma et al 2011 mAChR activation V1 =

Disney et al 2012 ACh application V1 =

Atallah 2012 GABA interneuron activation V1 =

Katzner et al 2011 GABA-A blockade V1 =

Alitto et al 2010 Anaesthesia LGN =

Wilson et al 2012 SOM interneuron activation V1

DOI

10.1111/j.1460-9568.2012.08052.x

10.1152/jn.00188.2012

10.1152/jn.00330.2011

10.1016/j.neuron.2011.12.013

10.1523/jneurosci.5753-10.2011

10.1113/jphysiol.2010.190538

10.1038/nature11347

Multiple pathways of BF influence on cortical activity

RN

basal forebrain

cortex

LGN

thalamus

fro

m r

etin

a

NBM

from

laye

r VI

nAChR

mAChR

Glutamatergic

GABAergic

Cholinergic

SOMATOSTATIN

PARVALBUMIN

V1 Interneuron stimulation

Wilson et al 2012

• Nicotinic AChR agonist application has largest effects on the contrast

response in the granular layer, targeting presynaptic nAChR on the

thalamocortical projections and up-regulating Glutamate release.

• Muscarnic AChR agonist application has largest effects on contrast responses

outside the granular cortical input layer.

• Both nAChR and mAChR agonists enhance contrast responsivity (Rmax) while

not afffecting contrast sensitivity (C50).

• The signature of basal forebrain activitation in cortex is enhanced gamma

range oscillations, which can take a broad band or peaked form. The peaked

form is likely cholinergic in origin.

• Basal forebrain deep brain stimulation results in enhanced contrast

responsivity, as well as greater sensitivity to contrast corresponding to reduced

C50 values. GABAergic projections from the basal forebrain to cortex that

target somatostatin-positive interneurons are likely to be the pathway

mediating these changes.

Take Home Message

Single object Object pairs

Basal forebrain neural ensembles exhibit -Frequency oscillations

during visual-reward learning

• Rats were trained with 3 LEGO objects, each of which was associated with a

specific reward value (high positive, low positive, mild aversive).

• They were then exposed to pairs of objects, and had to choose one of them to

receive the associated reward (decision task). Animals needed 2-3 days to

learn this decision task.

• Frequency oscillation bursts tended to occur around the time of the

decision, prior to object encounter, in the basal forebrain local field potential

(LFP). These bursts showed a tendency to be larger during the first day of the

visual-reward learning, linking basal forebrain activation to visual learning

processes.

Take Home Message

Nature 454, 1110-1114 (28 August 2008)

release bar reward

Acetylcholine contributes to attention in primary visual cortex through mAChR

Drug: Ach applied locally by Iontophoresis,

ACh application enhances neural tuning for bar length in V1, and

upregulates attentional modulation.

Ach Attentional Effects are reduced by mAChR blocker Scopolamine,

Acetylcholine biases processing in favour of sensory (subcortical) over lateral

(intracortical) inputs

Brain Research Volume 880, Issues 1-2, 13 October 2000, Pages 51-64

IC intracortical

SC subcortical

AC auditory cortex

Slice preparation

su

bco

rtic

al

intr

acort

ica

l

fast slow

fast slow

Layer 4 responses in

Auditory Cortex (AC)

CCh attenuates IC

fast potential more

than SC fast

potential

fast potential -> AMPA sensitive monosynaptic

slow potential -> polysynaptic

LOW CCh: strong reduction in slow potentials, fast potentials unaffected

• Acetylcholine contributes to attentional modulation in the primary visual

cortex through mAChR.

• Acetylcholine can bias cortical processing in favour of sub- or intracortical

inputs. High ACh is associated with domination of subcortical (thalamocortical)

inputs and perception of parts, whereas low ACh favors intracortical inputs and

holistic perception.

Take Home Message



DR, dorsal raphe





LC; locus ceruleus








Cholinergic CNS effects: Cholinergic Striatum Interneurons

Nucleus Accumbens (NAcc)

NAcc connects Putamen and Nucleus Caudatus of the Striatum

MSN (Medium Spiny Neuron) are the main neuron type in the Striatum

NAcc is major target of ventral tegmental area (VTA), involved in

reward/motivation pathway

Cholinergic Interneurons only account for 1-2% of Neurons.

Cholinergic CNS effects: Striatum Interneurons


MSN

Cholinergic Interneuron activation (mostly) inhibits MSN neurons

Cholinergic CNS effects: Striatum Interneurons


Cocaine-induced Place preference is abolished by silencing Cholinergic NAcc interneurorns.

• Cholinergic interneurons in the Nucleus Accumbens play an important role in

the motivation / reward network

• Optogenetic activation of these neurons mostly reduces firing rates of

medium spiny neurons, that make up the majority of NAcc neurons.

Conversely, inhibition of cholinergic neurons increases MSN activity.

• Silencing NAcc Cholinergic interneurons abolishes conditioned place

preference induced by Cocaine administration.

Take Home Message

Cholinergic CNS effects: LDT/PPT Thalamic pathway



DR, dorsal raphe





LC; locus ceruleus








Encephalitis Lethargica: Viral brain infection pandemic in early 1900s

In 1917, the Viennese Neurologist von Economo

observed large number of patients suffering from a

novel sleep disorder.

While they were able to stand, walk or communicate

normally, they would spontaneously fall asleep when

left alone. Many slept for 20hours per day. The

disease progresses quickly and could lead to death

within a period of a few weeks. Von Economo

observed, that a specific region in the brain stem

tended to show lesions in these patients.

Interestingly, he also described a small number of

patients suffering from insomnia. These patients

were found to have lesions confined to a small

region anterior to the other patients‘ lesion.

The disease turned out to be a viral pandemic,

which disappeared again as spontaneously as it had

appeared.

Based on these observations, von Economo

postulated the existence of a sleep center, which

inhibits neurons in a brain stem target region

responsible for arousal and wakefullness, thereby

inducing sleep.

VLPO, ventrolateral preoptic nucleus (lacks Ox receptors)

TMN, tubermomamillary nucleus

BF, basal forebrain

LC, locus coeruleus

LDT, laterodorsal tegmental nucleus

PPT, peduncopontine nucleus

PeF, perifornical area

Involvement of Cholinergic Centers in wake/sleep regulation

Nature 437, 1257-1263 (27 October 2005)

The Ascending Arousal System The VLPO Sleep Promotion System

The VLPO and the ascending arousal

systems form mutually inhibitory circuits that

prevent intermediate states between waking

and sleep.

Orexin acts to stabilize the system in the

awake or the sleep state, and prevents

intermediate states (Both humans and

animals spend only a small part of each day

(typically <1–2%) in transitional states)

A lack of orexins or their type 2 receptor can

cause symptoms of narcolepsy in

experimental animals, by destabilizing the

wake/sleep regulation mediated by Orexin.

(REM only) LDT / PPT

LDT / PPT

The flip/flop circuit of sleep regulation

Behavioural Brain Research Volume 115, Issue 2, November 2000, Pages 183-204

Adenosine promotes sleep by inhibiting Cholinergic activity

Caffeine, the most widely

used psychoactive drug is

an adenosine A1 and A2A

receptor antagonist

be

ha

vio

ral sta

te [%

]

Adenosine injection into

Cholinergic brainstem centers

cause sleep.

Adenosine builds up in parts of

the brain because the energy

supply (ATP) runs low. (ATP is

degraded to ADP, AMP and

eventually Adenosine)

NEJM Volume 348:2110-2124 May 22, 2003

The nicotinic ACh Receptor is a major target of general Anesthetics such as Isoflurane

• The wake/sleep cycle is governed by a brain stem circuit that

includes the VLPO (sleep center), which inhibits brain stem

centers controlling release of Acetylcholine and other

neuromodulators to the cortex.

• Caffeine is an Adenosine receptor antagonist. By blocking

Adenosine, Caffeine reduces Adenosine´s inhibitory influence

on Cholinergic neurons, leading to increased release of ACh and

arousal. Adenosine tends to build up during periods of

extended wakefullness, when ATP is running low. It returns to

normal levels after sleep.

• The nAChR is a major target of volatile anesthetics used

during general Anesthesia. It is an allosteric modulator of the

nAChR receptor, causing a strong reduction in excitatory

membrane currents mediated by nAChR. Other major targets are

the GABA-A and the glycine receptor.

Take Home Message

Cholinergic Neuromodulation II

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