Changes in spontaneous, odor modulated and shock induced behavior patterns following discrete olfactory system lesions

Abstract

Three groups of male hooded rats were preoperatively matched and then sham operated (SHAM), bilaterally lateral olfactory tract lesioned or anterior olfactory nucleus/anterior commissure lesioned. In one experiment, spontaneous behavior patterns emitted in an exploration field containing different odors were quantified during satiated and food deprived conditions. In other experiments, flinch and jump thresholds to electric shock and running patterns in an appetitively motivated straight alley experiment were measured. All lesioned animals were hyperactive and typically froze and groomed less than SHAMs while sniffing and rearing patterns differentiated the lesioned and SHAM groups in several ways. All animals had similar flinch and jump thresholds and also emitted similar types of responses to electric shock. In the straight alley, odors from normal and stressed rats had little effect on the running time of the experimental animals while a faint cat odor strongly inhibited SHAM running behavior. Responses to a novel chemical odor (trimethylpentane) and to changes in the alley floor or electric shock applied to the floor were minimal in all animals. The results were discussed against a background of other olfactory system lesions and some evidence separating the effects of olfactory cues from nonolfactory lesion effects was presented. Finally, problems associated with tests for olfactory discrimination were discussed. A need for more rigorous and specific discrimination tests in behavioral studies involving anosmia was emphasized.