George H. Crampton

8-OH-DPAT suppresses vomiting in the cat elicited by motion, cisplatin or xylazine

Vomiting was suppressed in cats pretreated with 8-OH-DPAT and then challenged with an emetic stimulus; motion, xylazine or cisplatin. The antiemetic effect is likely due to stimulation of postsynaptic serotonin-1A receptors. The most parsimonious explanation is that it acts at a convergent structure, presumably at or near the vomiting center. If so, 8-OH-DPAT may block emesis elicited by virtually any other stimulus. A supplementary experiment revealed that lorazepam suppressed motion sickness at a dose that produced ataxia, but did not suppress xylazine-induced emesis. These results do not support the possibility that the antiemetic effects of 8-OH-DPAT were the result of anxiolytic activity.

Systemic naloxone increases the incidence of motion sickness in the cat

Subcutaneous injections of naloxone in a total dose of 0.4 mg or greater one hour before a swing stimulus increased the frequency of motion sickness symptoms and shortened the latency of retching and vomiting.

Cerebrospinal fluid constituents of cat vary with susceptibility to motion sickness

Six female cats, varying in susceptibility to motion sickness, were implanted with chronic cannulae in the rostral portion of the fourth ventricle. The cats were then challenged with a motion sickness-inducing stimulus. Samples of cerebrospinal fluid were withdrawn before and after emesis or 30 min of motion if emesis did not occur and again on control (no motion) days. The samples were analyzed by HPLC with an array of 16 coulometric detectors. Thirty-six compounds were identified in the samples. Baseline levels of DOPAC, MHPGSO4, uric acid, DA, 5-HIAA and HVA were lower on motion and control days in cats which became motion sick when compared with cats which did not become motion sick. None of the identified compounds varied as a function of either exposure to motion or provocation of emesis. It is concluded that susceptibility to motion sickness is a manifestation of individual differences related to fundamental neurochemical composition.

Statistical analysis of censored motion sickness latency data using the two-parameter Weibull distribution

The suitability of the two-parameter Weibull distribution for describing highly censored cat motion sickness latency data was evaluated by estimating the parameters with the maximum likelihood method and testing for goodness of fit with the Kolmogorov-Smirnov statistic. A procedure for determining confidence levels and testing for significance of the difference between Weibull parameters is described. Computer programs for these procedures may be obtained from an archival source.

Research Strategies for Motion and Space Sickness

Research is urged for several motion sickness topics now receiving relatively little attention. The role of the area postrema, if any, is not completely resolved. The hypothesis that the cerebral spinal fluid might be a necessary neurochemical conduit should be confirmed or put to rest. It is surprising that the cerebellum, implicated more than 40 years ago, has not been reevaluated for its role in motion sickness in view of the explosion of new data on this structure. The sensory rearrangement theory, known by several names, needs direct experimental verification. One such experiment should determine if vestibular input is an essential element. Data interpretation problems related to rates of adaptation, often a consideration in sensory rearrangement experiments, are explored. The most exciting gains are to be achieved through neuropharmacologic approaches, particularly by exploiting the unique advantages offered by animal models.

8-OH-DPAT does not interfere with habituation to motion-induced emesis in cats

Experiments were performed to determine if suppression of motion-induced emesis (motion sickness) by 8-OH-DPAT altered the development or retention of habituation to the motion stimulus. Cats received 8-OH-DPAT followed by provocative motion on three consecutive treatment days. A drug-free test on the fourth day resulted in an incidence of emesis that was not different from that obtained on the fourth consecutive day of drug-free motion testing. Three consecutive days of treatment with 8-OH-DPAT without motion had no effect on the incidence of motion sickness on the fourth day. It was concluded that suppression of motion sickness by 8-OH-DPAT does not alter the acquisition or retention of habituation.