The use of the cochlear microphonic response as an indicant of auditory sensitivity: review and evaluation.
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Animals↗
Biomedical subjects
T G Raslear
Publications and source records attributed to T G Raslear.
A surgical technique for bilateral cochleotomy in the Long-Evans rat.
A bilateral cochleotomized surgical rat model, needed for a study involving microwave effects, was developed, standardized, and assessed for reproducibility. After a review of the literature concerning attempts and approaches with various species, a technique involving an approach through the external auditory canal was chosen and modified. Using a stereomicroscope, a cutaneous incision in the intertragic notch was made and extended medially along the ventral aspect of the external auditory canal to the depth of the external auditory meatus. The tympanic membrane was ruptured and the malleus removed with splinter forceps, allowing visualization of the cochlea. The lateral wall of the cochlea was penetrated with a 0.024-in. wire gauge drill bit and endolymph was suctioned from the cochlea. A 5-mm piece of 3-O silk suture, inserted into the cochlear opening, maintained patency. Appraisal of the reliability and standardization of the procedure was performed utilizing startleometry. Histology assessed completeness of the procedure and any evidence of cochlear infection.
Animals↗
The effects of diisopropyl phosphorofluoridate (DFP) on inter-response time and circadian patterns of lever-pressing in rats.
Rats were injected with saline, 1.0 mg/kg or 2.6 mg/kg of diisopropyl phosphorofluoridate (DFP). Three days later the animals were placed in cages in which they could press a lever to obtain their entire daily ration of food. The time of day at which responses occurred and the time between successive responses were recorded over a six day period to determine the circadian pattern of lever-pressing and the distribution of inter-response times (IRTs). The saline injected rats exhibited a normal nocturnal pattern of feeding, while both DFP treated groups exhibited a significantly greater tendency to eat during the day. Analysis of the IRT distributions of the three groups showed a different pattern of results. The saline and 1.0 mg/kg DFP groups produced nearly identical IRT distributions, while the 2.6 mg/kg group produced an IRT distribution which was marked by significant increases in the interquartile range and median IRT. Since the 1.0 mg/kg dose of DFP produced a circadian disruption but did not affect the IRT distribution, it appears that the disruption of circadian activity by DFP which was reported by Raslear and Kaufman cannot be solely explained by simple changes in the motor response.
Animals↗
Diisopropyl phosphorofluoridate (DFP) disrupts circadian activity patterns.
A single dose (1.75 mg/kg SC) of diisopropyl phosphorofluoridate (DFP) was given to rats living continuously in modified activity cages in which wheel running, lever pressing and feeding were monitored twenty four hours per day. The first twenty four hours following DFP injection was characterized by a marked reduction in all monitored activities. Within a few days, food intake and lever pressing had recovered to pre-injection levels, but running remained suppressed throughout the remainder of the experiment. A comparison of the circadian distribution of activities for individual subjects showed phase shifts and a reduction in amplitude of all three monitored activities, persisting well beyond the initial reductions in the daily totals.
Animals↗