Direct evidence of inter-hemispheric modulation by callosal fibers: a cortical spreading depression study in well-nourished and early-malnourished adult rats

• Published in: Experimental brain research 2008-03, Vol.186 (1), p.39-46
• Main Authors: Pinto, Ana Virgínia Oliveira, Guedes, Rubem Carlos Araújo
• Format: Article
• Language: English
• Subjects: Adults; Animals; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Body Weight; Brain research; Corpus Callosum - anatomy & histology; Corpus Callosum - pathology; Corpus Callosum - physiology; Corpus Callosum - physiopathology; Disease Models, Animal; Epilepsy; Female; Functional Laterality; Fundamental and applied biological sciences. Psychology; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Laboratory animals; Male; Malnutrition; Malnutrition - physiopathology; Medical sciences; Mental depression; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Nerve Fibers - physiology; Nervous system (semeiology, syndromes); Neurology; Neurosciences; Nutrition research; Pregnancy; Propagation; Protein-Energy Malnutrition - pathology; Protein-Energy Malnutrition - physiopathology; Proteins; Rats; Rats, Wistar; Reference Values; Research Article; Vertebrates: nervous system and sense organs; Weaning
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-007-1201-z

Inter-hemispheric modulation has been extensively studied, as it is critical for human behavior and could be involved in the development of neuropsychiatric disorders, such as major depression, epilepsy and stroke. Malnutrition early in life can alter brain processes such as inter-hemispheric modulation and these alterations can persist into adulthood. Here, we used cortical spreading depression (CSD) as a neurophysiological parameter to investigate inter-hemispheric modulation in 19 well-nourished and 18 early-malnourished male adult rats. CSD was evoked on the right frontal region and monitored at two parietal points on the same hemisphere. After a 2 h baseline recording, fibers projecting from the left to the right hemisphere via the corpus callosum were cut with a longitudinal lesion in the contralateral cortex and recording continued for two more hours. The results show that (1) baseline CSD propagation velocities were higher in the malnourished rats, as compared to the respective well-nourished controls; (2) post-lesion velocities increased in both nutritional groups, as compared with the baseline values; (3) this CSD increase persisted 3–7 days after lesion, suggesting a lasting effect and (4) in the malnourished group the post-lesion CSD enhancement was of smaller amplitude. Furthermore, a midline lesion (callosotomy) in eight well-nourished rats similarly facilitated CSD, suggesting the involvement of callosal fibers on this effect. No differences were found in sham-operated rats (21 well-nourished and 21 malnourished), as well as in a superficial (1 mm deep) contralateral lesion group (8 well-nourished). Results support the hypothesis of a lasting inhibitory contralateral influence on CSD propagation, which is attenuated, but not abolished, by early malnutrition.