Gripping the tail of taiep rats a myelin mutant is an effective way to induce cataplexy episodes: an ontogenetic study

J.R. Eguibar, M.C. Cortés, B. Gavito, A. Moyaho and J. Valencia

Institute of Physiology, Benemérita Universidad Autónoma de Puebla, Puebla, México

The taiep rat is a neurological mutant with immobility episodes (IEs) which are elicited by gripping the animal's tail or body (thorax). During cataplexic attacks the cerebral cortex is desynchronized and theta rhythm appears in the hippocampus, suggesting a REM sleep state. In previous experiments we alternated gripping the animal's body (B) and tail (T) to induce immobility episodes. The present study tested which method T or B is better to induce IEs in male and female taiep rats from 5 to 12 months of age.

 

Figure 1. Taiep rat during a cataplexic episode induced by gripping the animal's tail.

Animals were maintained under standard laboratory conditions. All experiments were done at 8:00 A.M. when an acrophase of gripping-induced IEs arises. We tested the feasibility and dependency on the order of execution of gripping-induced immobility methods by performing the four possible combinations (TT, BB, BT, TB). Gripping-induced IEs are more frequent after T than B. TT produced about 4.43 IEs out of 18 trials (24.6%), TB 3.67 (20.4%), and BT 4 IEs (22.2%), but BB only induced 1.38 IEs (7.7%). In the case of BT and TB 98% were induced bgripping the animal's tail. BB was statistically different from TT, BT and TB (ANOVA p<0.001, followed by Dunnett p<0.05). It was easier to induce IEs when the rats were between 7 and 8 months of age (ANOVA p<0.01); after that the frequency of IEs decreased with age. At 7 and 8 months of age, the number of gripping-induced IEs is sexually dimorphic, being the males more responsive.

These results show that gripping the animal's tail rather than its body produces IEs. Seemingly, differences between methods to induce immobility episodes are frequent. For instance, narcolpetic Doberman-Pinscher shows food-elicited cataplexy more frequently than play-elicited cataplexy. Taiep rats also show more IEs at 7-8 months of age with a marked sexual dimorphism, an interesting phenomenon that is worth studying further. In human beings too the cataplexic episodes are dependent on the age of the patient and are produced by a strong emotion. These results support that taiep rats are a suitable model to study cataplexy.

Supported by CONACYT, Mexico, grant 31758-N and VPPII-BUAP to JRE. MCC and BG have studentships from CONACYT.


Poster presented at Measuring Behavior 2000, 3rd International Conference on Methods and Techniques in Behavioral Research, 15-18 August 2000, Nijmegen, The Netherlands

© 2000 Noldus Information Technology b.v.