Chemosensory and hormonal mediation of social memory in male rats.

Abstract

The persistence with which adult male rats investigated a juvenile conspecific was significantly reduced following preexposure to either the juvenile or chemosensory stimuli (soiled bedding or urine) from that juvenile. The reduced persistence did not occur when the chemosensory stimulus came from a juvenile different from the one with which the subject was subsequently tested, which suggests the presence of a chemosensorily mediated social memory. It is suggested that any such memory may have adaptive value in that it permits a male rat to more readily identify a novel conspecific. Also, the lack of reduced persistence of social investigatory behavior in castrated subjects demonstrates the importance of male gonadal hormones in the formation, storage, and/or retrieval of the proposed chemosensorily mediated social memory.

Short-term social memory in the laboratory rat: its susceptibility to disturbance

“…Social discrimination in rats is regulated by the presence of olfactory cues (e.g. Sawyer et al, 1984), and investigation therefore takes the form of sniffing of the social stimulus, particularly focusing on the ano-genital region (Carr et al, 1976). The test is based upon a comparison of behaviour, particularly investigation, between two exposures of the same individual to a subject animal, separated by an inter-exposure interval (IEI).…”

“…Studies have indicated that it is unlikely, however, that odour deposition, either by the adults on the juveniles, or by the juveniles in the home cages of the adults, influences the outcome of the social recognition test (e.g. Sawyer et al, 1984;Perio et al, 1989).…”

Recognition of conspecific odors by laboratory rats ( Rattus norvegicus) does not show context specificity.

“…70.5s: Burman & Mendl 2000). However, previous research has indicated that both urine and soiled bedding can be used successfully to replace live conspecifics as stimuli in social recognition tests (Sawyer et al, 1984). Post-hoc analysis, in which context data were pooled and data for experienced and inexperienced groups analysed separately, revealed that for those rats without …”

The influence of preexperimental experience on social discrimination in rats (Rattus norvegicus).

“…It therefore appears that olfactory cues are able to represent the identity of individual animals -as demonstrated by the substitutability of urine or soiled bedding as social stimuli for live animals in recognition tests (e.g. Sawyer et al, 1984).…”

“…Kruczek 1998; an odour cue: e.g. Sawyer et al 1984) to a subject animal in order to encourage a habituation of stimulus investigation. The original 'habituation' stimulus and a 'novel' social stimulus are then introduced simultaneously, and stimulus investigation observed.…”