Morales MJJ, Pérez AMA, Nieto MOA

Language: Spanish
References: 10
Page: 161-163
PDF size: 245.17 Kb.

ABSTRACT

Background: The low temperature effects on auditory response in mammals, especially the man, causes that the brainstem auditory evoked potential (BAEP) disappear when the range of the corporal temperature from 20 to 27°C and convulsions take place when it arrives at the 20-21°C. However, in the reptiles the effect of the hypothermia have not been sufficiently studied.
Objective: To observe the disappearance of the auditory response of brainstem after submitting to the hypothermia to the reptilian and the progressive recovery of (BAEP) the in function of the increment of temperature-time.
Material and methods: The pattern of the brainstem auditory evoked potential in reptiles exposed to hypothermia was studied in a population of the prhynosomatid lizard Scelophorus torquatus (collar lizard) from the environs of Mexico City. The lizards were immersed in ice until their body temperature was between 0 and 4°C. BAEP was recorded then and subsequently (as body temperature increased) at intervals of approximately five minutes, until the record obtained became constant (and body temperature matched the air temperature).
Results: BAEP exhibited extremely low amplitudes and exceedingly long latencies at 4°C. As body temperature increased, BAEP wave latencies shortened steadily while amplitudes increased, also steadily, until an essentially constant response was obtained (about 25 min later). A correlation analysis showed a strong correlation between the temperature and the recovery of the auditory response.
Conclusions: Our results suggest that the brainstem is, from a phylogenetic point of view, primitively a highly damage-resistant structure (especially against generalized hypothermia) in amniotes. Thus, while low temperatures do affect the auditory response of the lizards, extending BAEP latencies while lowering its amplitudes, they do not produce permanent damage like in mammals.

REFERENCES

1. Dorfman LJ, Britt RH, Silverg GD. Human brainstem auditory evoked potentials during controlled hypothermia and total circulatory arrest. Neurology 1981;31:88- 89.

2. Marsh RR, Yamane H, Potsic WP. Auditory brain-stem response and temperature: relationship in the guinea pig. Electroenceph Clin Neurophysiol 1984;57:289-93.

3. Corwin JT, Bullock TH, Schwitzer J. The auditory brain stem response in five vertebrate classes. Electroenceph Clin Neurophysiol 1982;54:629-41.

4. Morales MJ, Solis H. Comparación de la respuesta auditiva del tallo cerebral entre Rana catesbiana (Anura: Ranidae) y Scelophorus torquatus (Sauria: Phrinosomatidae). Acta Zool Mex 1999;76:103-12.

5. Gerahard HC. Temperature coupling in the vocal communication system of the gray tree frog, Hyla versicolor. Science 1978;199:992-4.

6. Rose GB, Brenowitz EA, Capranica RR. Species specifity and temperature dependency of temporal processing by the auditory midbrain of two species of tree frogs. J Com Physiol 1985;157: 763-9.

7. Rubio T. Hypothermia chronic and syndrome of bad adaptation in river crocodile (Crocodylus marries acutus). Rev Biomed 2000;11:133-4.

8. Strain GM, Olcott BM, Thompson DR, Graham MC. Brainstem auditory evoked potential measurementes in holstein cows. Am J Vet Res 1987;6:162-9.

9. Schorn V, Lennon V, Rickford R. Temperature effects on the brainstem auditory evoked responses (BAEPs) of the rat. Biomed Symp 1977;16:313-8.

10. Stockard JJ, Sharbrough FW, Tinker JA. Effects of hypothermia on the human brainstem auditory response. Ann Neurol 1978;3: 368-70.