Transient attenuation of neuropathic manifestations in rats following lesion or reversible block of the lateral thalamic somatosensory nuclei.
OBJECTIVE
Nociceptive behavior in animal models for mononeuropathy has been shown to be altered by spinal tract lesions which suggest a possible supraspinal modulation. The thalamus constitutes a chief center for the processing of nociception. We have, therefore, investigated the effects of transient or permanent blocks of the lateral somatosensory thalamic nuclei (the ventrobasal complex) on the neuropathic manifestations in rats.


METHODS
Different groups of rats (n = 5-6) were subjected to mononeuropathy, following the spared nerve injury model, known to produce sustained heat hyperalgesia and tactile and cold allodynia which peaked about 2 weeks after nerve injury. This was followed by stereotaxic placement of either electrolytic or chemical lesions or implantation of mini osmotic pump for slow release of lidocaine in the ventrobasal complex.


RESULTS
Chronic electrolytic and chemical lesions or reversible block of the lateral somatosensory thalamus produced transient (1-2 weeks) attenuation of neuropathic manifestations along with a persistent decrease of the hot plate latency. The most pronounced effect was observed on heat hyperalgesia, and the least significant and short-lived effect was observed on cold allodynia.


CONCLUSIONS
We conclude that the lateral somatosensory thalamic complex is involved in the processing of neuropathic manifestations but cannot be considered as an obligatory or exclusive relay center for the neuropathic syndromes.
Saadé
N E
NE
Department of Human Morphology, Faculty of Medicine, American University of Beirut, Riad El Solh Beirut 1107-2020, Lebanon. nesaade@aub.edu.lb
Al Amin
H
H
Abdel Baki
S
S
Safieh-Garabedian
B
B
Atweh
S F
SF
Jabbur
S J
SJ
D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003080:Cold Temperature; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005260:Female; D006358:Hot Temperature; D006930:Hyperalgesia / Q000473:pathology; D007051:Ibotenic Acid / Q000633:toxicity; D007608:Kainic Acid / Q000633:toxicity; D020647:Lateral Thalamic Nuclei / Q000187:drug effects*; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009407:Nerve Block; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects; D010523:Peripheral Nervous System Diseases / Q000473:pathology*; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D013127:Spinal Nerves / Q000293:injuries; D013238:Stereotaxic Techniques
D000779:Anesthetics, Local; D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid; D008012:Lidocaine; D007608:Kainic Acid