Autor(es):
Almeida, Hugo Leite 
; Fernandes, Ana Valle ; Almeida, Armando
Data: 2006
Identificador Persistente: http://hdl.handle.net/1822/5186
Origem: RepositóriUM - Universidade do Minho
Assunto(s): Supraspinal circuitry; Medullary reticular formation; Pain pathways; Cholera toxin subunit B; Biotinylated dextran; Brain efferents
Descrição
In the last 15 years a role has been ascribed for the
medullary dorsal reticular nucleus as a supraspinal pain modulating
area. The medullary dorsal reticular nucleus is reciprocally
connected with the spinal dorsal horn, is populated mainly
by nociceptive neurons and regulates spinal nociceptive processing.
Here we analyze the distribution of brain projections
from the medullary dorsal reticular nucleus using the iontophoretic
administration of the anterograde tracer biotinylateddextran
amine and the retrograde tracer cholera toxin subunit B.
Fibers and terminal boutons labeled from the medullary dorsal
reticular nucleus were located predominately in the brainstem,
although extending also to the forebrain. In the medulla
oblongata, anterograde labeling was observed in the orofacial
motor nuclei, inferior olive, caudal ventrolateral medulla, rostral
ventromedial medulla, nucleus tractus solitarius and most of
the reticular formation. Labeling at the pons-cerebellum level
was present in the locus coeruleus, A5 and A7 noradrenergic
cell groups, parabrachial and deep cerebellar nuclei, whereas in
the mesencephalon it was located in the periaqueductal gray
matter, deep mesencephalic, oculomotor and anterior pretectal
nuclei, and substantia nigra. In the diencephalon, fibers and
terminal boutons were found mainly in the parafascicular, ventromedial,
and posterior thalamic nuclei and in the arcuate,
lateral, posterior, peri- and paraventricular hypothalamic areas.
Telencephalic labeling was consistent but less intense and concentrated
in the septal nuclei, globus pallidus and amygdala.
The well-known role of the medullary dorsal reticular nucleus
in nociception and its pattern of brain projections in rats
suggests that the nucleus is possibly implicated in the modulation
of: (i) the ascending nociceptive transmission involved in
the motivational-affective dimension of pain; (ii) the endogenous
supraspinal pain control system centered in the periaqueductal
gray matter–rostral ventromedial medulla–spinal cord
circuitry; (iii) the motor reactions associated with pain.
