Genetic dissection of medial habenula–interpeduncular nucleus

pathway function in miceYuki Kobayashi, Yoshitake Sano, Elisabetta

Vannoni, Hiromichi Goto, Toshio Ikeda, Hitomi Suzuki, Atsuko Oba, Hiroaki Kawasaki, Shigenobu Kanba, Hans-Peter Lipp, Niall P. Murphy,David P.

Wolfer and Shigeyoshi Itohara

Presented by: Justin P. Smith

Fineberg Review

• Impulsivity- a predisposition toward rapid, unplanned reactions to internal or external stimuli with diminished regard to the negative consequences of these reaction to the impulsive individual or to others

Fineberg Fig 1

IPN

Neurocognitive domain Definition Task Neural system Neurochemistry

Impulsivity

 Motor impulsivity Prepotent motor disinhibition

Stop signal reaction time task (SSRT)

Right inferior frontal cortex and subcortical

connectionsNorepinephrine

 Decision-making impulsivity

Difficulty in delaying gratification and

choosing immediate small rewards despite

negative long-term consequences

Decision making or gambling tasks (eg

Cambridge Gambling Task (CANTAB), Iowa

gamble task)

Orbitofrontal cortex and subcortical

connections

Cortex—serotonin Subcortical circuitry-serotonin/dopamine

 Reflection impulsivity

Insufficient information sampling before making a choice

Reflection task, 5-CSRTT Not known Not known

Table 1

Role of 5-HT (Table 2)

Compulsivity (reversal learning task)

Impulsivity (5CSRTT)

5-HT2C antagonist (SB24284)

ReducedIncreased

5-HT2A antagonist (M100907)

Increased Reduced

Hypothesized- mediating neuroanatomy

Neural projections from OFC to the caudate nucleus (dorsomedial striatum in the rat)

Neural projections from VMPFC (area 25) to the shell of the nucleus accumbens

Impulsivity (5CSRTT)

5-HT2C antagonist (SB24284) Increased

5-HT2A antagonist (M100907) Reduced

Hypothesized- mediating neuroanatomy

Neural projections from VMPFC (area 25) to the shell of the nucleus

accumbens

Heldt and Ressler

• Habenula (Hb) modulates DA and 5-HT• Lesioned Hb • Tested ± DA agonist (apomorphine) or DA/5-HT antagonist (clozapine)

– Fear-potentiated startle – Freezing– Conditioned fear– Prepulse inhibition (PPI)– Locomotion

Heldt and Ressler

• No stress = no difference• Following Conditioned Stress (lesioned animals)

– ↓ PPI, normalized with DA/5-HT antag (clozapine)– DA agonist (apomorphine) = hyperlocomotion

– Hb involved in stress-dependent regulation of monoamine systems

Heldt Ressler Fig 3

Main paper

• Created genetic ablation of mHb• Subdivide Hb into medial (mHb) & lateral (lHb)• mHb- nicotinic acetylcholine R’s– α3,α5 & β4 subunits

• mHb-interpeduncular nucleus (IPN) pathway • Behavioral role- ↓ cognition-dependent

executive fxns

Behavior

• Males for classic tests• Females for IntelliCage study• Nicotine subcu groups– 0, 0.35, 1.05, 3.5, 10.5, and 35 μg/kg – once daily, – 10 min prior to the task

α5 subtype in mHb cells role limiting mHb–IPN pathway & nicotine intake

Fig 1

Characterization of mHb-specific Cre expression transgenic mice

Show us they have targeted the mHb

Fig 2 mHb-selective lesions in mHb:DTA mice

Successful genetic lesion of mHb

Monoamines and metabolites

Behavior

• Locomotor activity in home cage• mHb:DTA mice had no new environment

habitation• 5-choice serial reaction time task (5-CSRTT)• Prepulse Inhibition• Open field• EPM

Fig 3

Locomotor activity

PPI Open fieldEPM

5-CSRTT

Delayed and Effort based decision making (ish)

• T-maze• ↑ reward (HRA; 10 pellets), ↓reward (LRA;1 pellet)

• Delay-trained to wait (5, 10 then 15s) for HRA• Effort- small 15cm obstacle in HRA, LRA open

Fig 4: Delay top, Effort bottom Black = control

Learning and memory tests

• Morris water maze• Fear conditioning• Radial arm maze

Fig 5

Morris water maze

Fear conditioning

Radial arm maze

IntelliCage (females)

• Activity and Adaptation– Visits to water bottle– Week 1 all doors were open, access 8 drinking

bottles (free adaptation)– week 2 doors closed, opened with 5 s nose-poke

(nose-poke adaptation)– 3rd week fixed drinking schedule (drinking session

adaptation) opening to nose-pokes between the hours of 11am–noon and 4pm–5pm

IntelliCage

• Corner avoidance task (Avoidance and preference)

• Trained to drink from specific corners• Air puff to face if incorrect

Fig 6: IntelliCage

reversal

Flexibility• Chain task reward

– water same corner for 14 sessions (corner preference), – 14 sessions water in opposite corner (corner reversal) – 8 sessions learn new corner during each drinking session (serial

reversal)• Cage mates in four subgroups, target corners

– water delivered in corner adjacent to most recently visited one – 14 sessions in one direction (chaining acquisition) – 21 sessions in the opposite direction (chaining reversal)– Water in the corner adjacent to the last rewarded corner

(patrolling acquisition) clockwise or counter clockwise– 21 sessions in opposite direction (patrolling reversal)

Reaction time and Saccharin preference

• Reaction time– Nose poke with light cue and allow drinking– Nose poke during delay = premature response

• Saccharin preference– Preference for sweet water– Must wait timeout period (increases per day)

Chaining Chaining Patrolling Patrolling

Reaction Time

Saccharin preference Saccharin delay

Fig 7: Lack of susceptibility to nicotine in mHb:DTA mice on 5-CSRTT performance and adaptation to a new environment

• Effects of nicotine on the new environment adaptation task

• Nicotine failed to induce any effect

• Mhb-IPN central pathway on inhibitory and environmental adaptation

c-Fos expression

• Measure of activity• Sampled from 5-CSRTT • Reflect differences in the genotype• Suggest a crucial involvement – ACC and hippocampus in the behavioral

abnormalities of mHb-DTA mice

Fig 8

Take home• mHb-IPN pathway involved– inhibitory control (impulsive and compulsive behaviors)– Executive functions

• mHb:DTA resemble phenotypes with bilateral lesions habenular complex

• mHb:DTA lack susceptibility systemic nicotine– supports mHb–IPN pathway, expresses a ↑level of

unique nicotinic acetylcholine receptors (α3,α5 & β4)• mHb–IPN–monoaminergic centers & lHb-

mediated pathway essential for controlling monoaminergic centers (mech unknown)