The Effects of the Hallucinogen DOI on the Novel Object Recognition Task and Conditioned Place Preference Within the Rat Model

Mitchell MorningstarSponsor: George Rebec

Introduction: Motivation

Return of psychedelic assisted psychotherapies MDMA1

LSD2

Psilocybin3 Effects of psychedelics on

healthy individuals Good Friday study + subsequent

follow up4,5

Present work6

1. Mithoefer. 2011. J Psychopharmacol.2. Gasser. 2014.3. Johns Hopkins. Unpublished.4. Pahnke. 1963. Harvard PhD

Dissertation5. Doblin. 1991. J Transper Psycho.6. Griffiths et al. 2011. Psychopharm.

Introduction: Serotonin (5-HT)

Serotonin 2A (5-HT2A) agonism is thought to be the primary mediator of psychedelic activity1

▪ Expressed widely throughout the brain – highest within frontal cortex2

▪ Sensory cortices, basal ganglia, locus coeruleus, ventral tegmental area, and hippocampus also have some expression3

Other receptors talked about will be 5-HT2B, 5-HT2C

Frontal cortex

Basal Ganglia

Sensory cortices

HippocampusVentral Tegmental

Area

Locus Coeruleu

s

1. Vollenweider. 1998. Neuroreport.2. McKenna and Saavedra. 1987. Eur J Pharm. 3. Wong et al. 1987. Synapse.

Introduction: DOI

2,5-dimethoxy-4-iodoamphetamine (DOI) is a 5HT2A receptor agonist1

Similar to classical hallucinogens such as LSD, psilocybin (shrooms), and DMT

Active at 5-HT2A, 5-HT2B, 5-HT2C1

Hallucinogenic phenethylamine Produces head-twitch response2

Currently unregulated, not a popular recreational drug Long duration 1. Canal. 2012.

Drug Testing and Analysis

2. Keller. 1956. Science.

Introduction: Behavioral Effects

5HT2A activation… Alters time perception and perception of light1 Increases acquiring of associative learning, classical

conditioning responses2

Increases memory consolidation3

5HT2A blockade decreases rodent’s ability to retrieve complex memories4

1. Hanks. 2012. ACS Chem. Neuro.

2. Harvey. 1996. Behav. Brain Research.

3. Zhang et al. 2013. Front. Pharm.

4. Bekinschtein. 2013. J. Neuroscience

Introduction: Behavioral Tasks Novel Object Recognition (NOR) task tests rodent’s ability

to remember where and what Able to do so because of rodent’s innate preference for novel,

new objects in environment1 Entorhinal cortex and hippocampus are important areas for

storing, encoding and retrieving memories related to the NOR task2

Conditioned Place Preference (CPP) is often used to measure rewarding effects of drugs3

Associative learning – drug paired side becomes a conditioned stimulus able to cause rodent to preference it 3 1. Bevins. 2006. Nature Prot.

2. Cohen et al. 2015. Behav. Brain Research

3. Huston. 2013. Cell.

Hypothesis

Rats injected with DOI (0.2 mg/kg, i.p.) won’t be able to discriminate between the novel and familiar objects in the novel object recognition task.

Rats injected with DOI (0.2 mg/kg, i.p.) will spend less time in the drug-paired side of a conditioned place preference task.

Methods Novel Object Recognition (NOR) Three Phases

▪ Habituation▪ 10 Minutes of Free Roaming

▪ Familiarization▪ 10 Minutes with 2 Objects

▪ Trial▪ Delay of 1 hour▪ Injection (i.p.) 30 minutes into hour▪ One object is replaced with a new, novel

object▪ 5 Minute trial period

Time spent with each object was measured

Counterbalanced, data normalizedA B C

Figure adapted from Bevins 2006

A B CA

One placement (10 minutes)

One placement(5 minutes)

Methods

Conditioned Place Preference (CPP) 3 days of baseline data recorded to find

initial side preference Cocaine was paired on side least preferred Eight days of conditioning starting with

cocaine Tested 48 hours after last conditioning trial DOI or Saline injection given 30 minutes

prior to CPP test Time measured with digital stopwatches Biased

3 Days of Drug Naive

Baseline Data

Conditioning beginning with

cocaine (12.5 mg/kg), alternating to

saline

Saline or DOI (0.2 mg/kg)

pretreatment prior to assessing

CPP

Results: NOR

• Ratio of time spent with novel object

• Rats with DOI on-board during the testing phase

• Significantly worse at differentiating the novel object from the object they had been familiarized to 1 hour prior

n = 7 n = 7

Group TypeDOI Saline

Mea

n D

iscr

imin

atio

n R

atio

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

***

t(12) = -2.45, p < 0.05

Novel Object Recognition Results

n = 7 n = 7

Results: NOR

Group TypeDOI Saline

Tota

l Tim

e S

pent

With

Bot

h O

bjec

ts

0

5

10

15

20

25

30

35

40

45

50

t(12) = -2.00, p = 0.0914

Total Time

• Total time spent• No significant difference

between groups

n = 7 n = 7

Results: CPP

DOI Treated Group Saline Treated GroupPre

fere

nce

(sec

s) |

Dru

g P

aire

d S

ide

- Sal

ine

Pai

red

Sid

e

-100

-80

-60

-40

-20

0

20

40

60

80

100

***

• DOI decreases time spent on drug-paired side

• Animals treated with DOI did not have a preference for the drug-paired side

• Animals treated with Saline did have a preference for the drug-paired side

• A significant difference was found between the two groups

n = 4

n = 4

Results: CPP

DOI Treated Group Saline Treated Group

Per

cent

age

of B

asel

ine

0

20

40

60

80

100

120***

*

**

Percentage of Baseline Per Group

Saline PairedDrug Paired

• Figure describes the amount of time spent per side in each group as compared to baseline taken prior to cocaine conditioning

n = 4 n = 4

Results: Summary

Deficits in the NOR task were found suggesting that on-board DOI impairs object recognition memory No significant difference between the on-board DOI and

saline groups were found in overall time spent with both objects.

CPP was attenuated with DOI on-board suggesting that 5-HT2A agonism could be a target of attenuating the rewarding properties of drugs of abuse

Conclusion DOI decreased performance in the NOR task while

attenuating cocaine-induced CPP Recognition of the familiar object and recognition of the CS

were impaired, whether this is upstream perceptual deficit or downstream memory deficit can’t be determined

Future studies could employ region specific pharmacological manipulations while also utilizing electrophysiology in order to find changes in neuronal response

Future studies can further investigate the effects of 5-HT2A on memory, perception, and locomotion

Questions?