Multisensory deficits in rats produced by acute exposure to cold swim stress.

Cold swim stress and morphine administration produce analgesia. Whether this was accompanied by changes in other senses was investigated. Analgesia was assessed with a tail-flick test; the sensitivity of the other senses was assessed using the ability of mild sensory stimuli (prestimuli) to inhibit the amplitude of a subsequently elicited acoustic startle response. In Experiment 1, auditory prestimuli were used. In Experiment 2, visual prestimuli were used. In each experiment, rats were exposed to cold-water swims followed by behavioral testing, warm swims followed by testing, and testing alone. This was repeated, substituting morphine injections followed by testing, vehicle injections followed by testing, or testing alone. Both cold swim stress and morphine produced reliable analgesia. Only cold swim stress interfered with the ability of the stimuli to inhibit startle. This reflects decreased sensitivity to auditory and visual stimulation caused by cold swim stress, which suggests that the resultant sensory deficits are more global than is currently believed.