Reversible attenuation of neuropathic-like manifestations in rats by lesions or local blocks of the intralaminar or the medial thalamic nuclei.
Author: Saadé NE, Al Amin H, Abdel Baki S, Chalouhi S, Jabbur SJ, Atweh SF.
Source:
Experimental neurology, 204(1), 205-219.
BACKGROUND AND AIM: Thalamic somatosensory nuclei have been classified into
medial and lateral systems based on their role in nociception. An imbalance
between these two systems may result in abnormal somatic sensations and
spontaneous pain. This study aims to investigate the effects of transient or
permanent block of the medial and intralaminar nuclear groups on the
neuropathic-like behavior in a rat model for mononeuropathy. METHODS: Neuropathy
was induced on one hind paw in different groups of rats following the spared
nerve injury model. When the resulting hyperalgesia and allodynia (tactile and
cold) reached a maximum plateau, the rats received either chemical or
electrolytic lesion or lidocaine (2%) microperfusion, placed in the various
thalamic nuclear groups. RESULTS: All procedures produced transient but
significant decrease of neuropathic manifestations. The magnitude and duration of
decrease depended on the type and the site of the block. These effects can be
ranked in increasing order as follows, electrolytic<chemical<lidocaine
micro-perfusion according to the procedure, and as
rostro-medial<ventro-median<parafascicular nuclei, according to the site of the
block. Thermal hyperalgesia was the most affected while cold allodynia showed the
least attenuation. Neuropathic manifestations returned to their pre-lesion levels
after 2-3 weeks, along with frequently observed delayed hyper-responsiveness to
the hotplate test. CONCLUSION: The observed results demonstrate the involvement
of the medial and intralaminar thalamic nuclei in the processing of
neuropathic-like manifestations, and the reversibility of the effects suggests
the flexibility of the neural network involved in supraspinal processing of
nociceptive information.