DIAGNÓSTICO

3.5.1. Distribution of neurokinin-1 receptor immunoreactivity in the mouse brain

Im m u n o re a c tiv ity fo r the N K l re c e p to r in the m ouse b ra in was strongest in the CPu, the N A c c core and sheU subregions, the habenular nucleus, the lateral geniculate nucleus, the intergenicu late leaflet, the parabrachial nucleus and the locus coeruleus, w ith weaker sta in in g observed in c o rtic a l areas, the hypothalam us, the central, basom edial and m edial

Chapter three Immunohistochemical detection o f the neurokinin-1 receptor

n u cle i o f the amygdala, the amygdala’s accessory regions, the dorsal periaque ductal grey, the tegm ental p e n d u n c u lo p o n tin e nucleus and dorsal and m edial raphe nuclei. N K l im m u n o re a c tiv ity was generally absent fro m the hippo ca m p u s, tha la m ic regions, the substantia nigra, the V T A and the cerebellum . H o w e v e r, sections caudal to the level o f the locus coeruleus (a p p ro xim a te ly 6 m m caudal to Bregm a) w ere n o t analysed, c o m p ris in g the m edulla oblong ata and brainstem nuclei. S im ilarly, sections ro s tra l to the p re fro n ta l cortex (a p p ro xim a te ly 2 m m ro stra l to Bregm a) w ere n o t exam ined, thereby o m ittin g the o lfa c to ry bulbs fro m analysis.

3.5.2. Comparison of mouse and rat neurokinin-1 receptor distributions

T h e d is trib u tio n o f im m u n o re a c tiv ity fo r the N K l re ce p to r in the m ouse b ra in is very sim ila r to th a t in the ra t (Nakaya

et al.

1994), and generally agrees w ith fin d in g s in this and o th e r species using IH C , and usin g labelled N K l re c e p to r agonists o r

in situ

h yb rid isa tio n . T h is sim ila rity is also reflected in the expression o f C h A T in the N K l receptor-expressing neurones o f the m ouse C P u and N A c c , as c o n firm e d w ith dual-la b e llin g IH C (M u rtra

et ai,

u n p u b lish e d observations). H o w e ve r, in the hipp o ca m p u s, the p a tte rn o f im m u n o re a c tiv ity d iffe rs betw een the present study and p revious studies in the rat. H ere, N K l im m u n o re a c tiv ity was n o t seen in the d o rso ro stra l h ip p o ca m p u s in any o f the brains analysed, w h ils t at m o re ventro ca u d a l levels o f the h ip p o ca m p u s and the su b icu lu m , N K l re c e p to r-p o s itiv e cells w ith p yra m id a l cell-Uke m o rp h o lo g y w ere occasionally seen (data n o t show n). In the rat, N K l re ce p to r im m u n o re a c tiv ity is re p o rte d to be o f h ig h in te n sity and density in the hüus o f the dentate gyrus, as w e ll as o n G A B A e rg ic in te m e u ro n e s o f the C A l and C A 3 subregions (Acsady

et al

1997; N akaya

et a l

1994; S lo v ite r

et al

2001). F u rth e r m in o r differences betw een this and p revious studies w ere observed in the septal nuclei, the amygdala and the thalam us. A lth o u g h N K l re c e p to r im m u n o re a c tiv ity was observed in the septum o f the m ouse, especially the m edial septal nucleus, i t was o f lo w e r relative in te n s ity than in the rat. Sim ilarly, the density o f N K l re c e p to r-im m u n o re a c tiv e neurones in the lateral and basolateral n u cle i o f the amygdala was n o tice a b ly lo w e r in the m ouse than in the rat, a lth o u g h the p a tte rn o f N K l re ce p to r d is trib u tio n across the amygdala’s subnuclei was com parable. F inally, the lo w levels o f N K l receptor im m u n o re a c tiv ity in the m id lin e nuclei o f the ra t thalam us, such as the parafascicular nucleus, w ere n o t observed in the present study. E lsew here in the b ra in there were few

Chapter three Immunohistochemical detection o f the neurokinin-1 receptor

q u a lita tive differences in the d is trib u tio n o f im m u n o re a c tiv ity betw een species, alth o u g h differences m ay exist in the areas o f the b ra in n o t exam ined in this study, such as the o lfa c to ry bulbs and the m edulla oblongata.

3.5.3. Mismatch between substance P and the neurokinin-1 receptor

T h e expression o f the N K l re c e p to r in the ra t fo llo w s th a t o f SP re la tive ly closely. H o w e v e r, there are a fe w areas o f m ism a tch o f the re ce p to r and its p re fe rre d ligand, m o st n o tice a b ly in the substantia nigra pars reticulata. T h is b ra in re g io n possesses h ig h levels o f SP b u t seems to be d e v o id o f N K l receptors, at least in the m a jo rity o f p u b lish e d studies (G e rfe n 1991; M ae n o

et al.

1993; M a n ty h

et al.

1984; N akaya

et a l

1994; R o th m a n

et ai

1984; Shults

et al

1982). C onversely, the hilus o f the dentate gyrus, w h ic h is ric h in N K l re c e p to r-p o s itiv e dendrites in the rat, expresses lo w levels o f SP (Nakaya

et a l

1994). In the absence o f a system atic analysis o f the expression p a tte rn o f SP in the m ouse, a com parison o f the expression patterns o f the re ce p to r and lig a n d

in

this species is n o t possible. H o w e v e r, in a p re lim in a ry study, the expression p a tte rn o f SP im m u n o re a c tiv ity in the m ouse fo re b ra in was fo u n d to be sim ila r to th a t o f the N K l re c e p to r (data n o t show n).

3.5.3. Methodological considerations

A lth o u g h the present results are sim ila r to those observed in o th e r species, the correspondence o f the d is trib u tio n o f N K l re ce p to r im m u n o re a c tiv ity to the d is trib u tio n o f the re ce p to r its e lf is dependent u p o n the sp e cificity o f the p rim a ry an tib o d y. T h e a n tib o d y used was purchased fro m C h e m ico n In te rn a tio n a l, w h o claim th a t i t is specific fo r the N K l receptor, reacting w ith th a t o f the guinea pig, m ouse o r ra t (see section 2.4.2). T h e observed staining p a tte rn sh o u ld th e re fo re co rre sp o n d exactly to the re c e p to r’s d is trib u tio n . F u rth e rm o re , the present fin d in g s have been c o n firm e d in the m ouse using tw o o th e r p rim a ry antibodies raised against the N K l re ce p to r (in c lu d in g an a n tib o d y raised against the a m in o acid sequence o f the m ouse N K l re ce p to r; see section 2.4.2), adding w e ig h t to the c o n clu sio n th a t the observed differences betw een this study and p revious ra t studies are due to a real interspecies d iffe re n ce rather than b e in g a m e th o d o lo g ic a l artefact.

Chapter three Immunohistochemical detection o f the neurokinin-1 receptor

In document Eficacia del tratamiento fisioterapéutico en pacientes con radiculopatías que acuden al centro medical rehabilitic en el periodo julio diciembre 2010 (página 45-49)