Title

Social habituation and dishabituation in CD-1 mice treated with the norepinephrine neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4)

Date of Award

1998

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Advisor(s)

Catherine Cornwell

Keywords

Chloroethyl ethyl bromobenzylamine, Odor recognition, Habituation, Norepinephrine

Subject Categories

Psychology

Abstract

Male CD-1 mice between postnatal days 60 and 90 were injected intraperitoneally (i.p) with either water vehicle (controls) or 50$\mu$g/g of the norepinephrine neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). They were tested 3 to 6 days later on the odors of adult males in a four-trial habituation/dishabituation paradigm. There were four groups: group CSS were water injected and exposed to the same male on all four trials; group CSN were water injected and exposed to the same male on the first three trials and a novel one on the fourth; group DSN were DSP-4 treated and exposed the same male on the first three trials and a novel one on the fourth; and group D0-N were exposed to the empty apparatus on the first three trials and to a novel male on the fourth.

All groups showed a significant decline in screen investigation time between the first and second trials, an indication of habituation to the overall testing environment. Group CSS demonstrated a progressive decrease in screen investigation time with the least investigation time occurring on trial 4. Group CSN demonstrated a similar pattern of diminishing screen investigation time over the first three trials, but stopped diminishing on the fourth trial when a new stimulus animal was placed in the cage. Animals from the DSN group did not demonstrate a quantitative change in screen investigating time at all. Screen investigation time of the D0-N group decreased progressively over the first three trials but increased sharply on trial 4 to trial 1 levels.

These results suggest that animals from the CSN group could distinguish between the odors of a familiar and novel animal while those from the DSN group could not. Thus DSP-4 treatment may have impaired the ability of the animals to recognize the odors of a familiar versus an unfamiliar conspecific. This failure of recognition was not due to anosmia since animals from the D0-N group habituated to the testing environment showed a strong dishabituation response when exposed to a novel animal. In addition, on an olfactory preference test, all groups showed a preference for a familiar botanical odor (hardwood) over a nonfamiliar one (pine). Taken together, these results suggest that central NE is a modulator of intermale social olfaction.

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