upper and lower limb innervation is greatly affected by brachial and lumbosacral plexus lesion , leading to loss of motor and sensory function [ 17 ] . in the neonate ,
such injuries are even more harmful , since surgical treatment is limited and neuronal loss is particularly enhanced by neurotrophic factors deprivation . nonexistent or limited handling of neonatal proximal lesions results in limb dysfunction and neuropathic pain [ 812 ] .
experimentally , a well - accepted model to mimic axotomy injury retrograde repercussion to spinal neurons is the neonatal peripheral nerve axotomy [ 1318 ] .
sciatic nerve transection , early after birth , results in significant degeneration of spinal motoneurons as well as sensory neurons present in the dorsal root ganglia .
also , a number of interneurons , present in deep spinal cord laminae , degenerate due to the loss of input and/or output .
importantly , exogenous treatment with neurotrophins transiently rescues a significant number of neurons , leading to the possibility of axonal regrowth and regeneration [ 19 , 20 ] . to date , neonatal peripheral nerve repair following neurotmesis is largely limited due to technical drawbacks .
in fact , to perform end - to - end coaptation by epineural / perineural suturing in the newborn represents a major challenge . on the contrary ,
reconnection of transected stumps by using biocompatible sealants may significantly facilitate the process , as well as taking the advantage of employing the adhesive as scaffold to engraft stem cells , as well as neurotrophic substances , to the injury site .
fibrin sealant has been applied in neurosurgery for decades , being effective and biocompatible , with no side effects to the nervous system microenvironment .
together , when activated , their interaction mimics the coagulation cascade , forming a stable and adhesive clot .
regard , much effort by the center for the study of venoms and venomous animals ( cevap ) has been made to produce a new fibrin sealant that uses a serine protease from a brazilian snake ( crotalus durissus terrificus ) with thrombin - like activity .
also , in order to avoid human blood , bubaline - derived blood serum cryoprecipitate has been used as the fibrinogen source . among several advantages ,
the nonhuman fibrin glue hampers transmission of hepatitis and hiv / aids [ 2327 ] .
also , it has a customizable formulation that can be adjusted to increase or decrease fibrin clot formation and stability . although anatomical repair of spinal roots and other lesioned plexus components constitute the primary approach , additional strategies are necessary to enhance neuroprotection and to improve the regenerative response of severed neurons .
this may be achieved by stem cell therapy that has shown particularly important positive effects following nervous system injury [ 2837 ] . in this regard , we have already shown evidence that mononuclear cell therapy produced neuroprotection , preservation of synapses in the spinal cord , and reduction of glial reaction following dorsal and ventral horn adult lesion [ 38 , 39 ] .
the present work investigated the viability and efficiency of neonatal sciatic nerve end - to - end coaptation , performed with the application of fibrin sealant .
we show that both commercial and customized nonhuman fibrin adhesives perform equally well and allow motor and sensory recovery up to 12 weeks after injury .
nerve stumps coaptation was performed by using either a commercially available fibrin sealant - tissucol ( baxter , vienna , austria ) or a patented fibrin sealant derived from snake venom , kindly supplied by the center for the study of venoms and venomous animals ( cevap ) of unesp ( patent registration numbers br1020140114327 and br1020140114360 ) . at the time of use
, the components were previously thawed , reconstituted , mixed , and applied [ 2427 , 31 ] .
two - day - old ( p2 ) neonatal lewis rats were anesthetized by hypothermia and subjected to unilateral sciatic nerve transection at mid - thigh level .
animals were divided into three groups : axotomy alone ( ax , n = 30 ) , in which a 2  mm segment of the proximal stump was resected in order to assure absence of contact between stumps ; axotomy followed by end - to - end cevap 's fibrin sealant coaptation ( ax+fs , n = 30 ) ; axotomy followed by end - to - end commercial fibrin sealant coaptation ( ax+cfs , n = 30 ) .
an overview of the surgical procedure is illustrated in supplementary figure s1 ( in supplementary material available online at http://dx.doi.org/10.1155/2016/9028126 ) .
an additional nonoperated control group was specifically utilized for the motor test evaluation ( n = 5 ) .
also , in order to evaluate the retrograde degeneration of motoneurons following nerve transection without proximal stump resection , an additional axotomy control group was evaluated following stump reapposition ( ax - sr ; n = 5 ) .
both fibrin sealants used herein are composed of three separate solutions : ( 1 ) fibrinogen , ( 2 ) calcium chloride , and ( 3 ) thrombin or thrombin - like ( in the case of the serine protease derived from snake venom ) . during surgical repair ,
the first two components were applied and the proximal and distal stumps were approximated in an end - to - end fashion .
the sciatic nerve was gently shifted to assure the stability of the coaptation and to evaluate the success of the repair .
the institutional committee for ethics in animal ( ceua / unicamp ) and the center of experimental and ethical animal ( ceea / unesp ) approved all experiments ( proc .
number 2593 - 1 and 904 - 2011 , resp . ) , which were performed in accordance with the guidelines of the nih and the brazilian college for animal experimentation .
the animals were housed using a 12  h light / dark cycle and controlled temperature ( 23c ) , with free access to food and water .
animals were anaesthetized with an overdose of kensol ( xylasine , kning , argentina , 10  mg / kg ) and vetaset ( ketamine , fort dodge , usa , 50  mg / kg ) , and the vascular system was rinsed by transcardial perfusion with phosphate buffer 0.1  m ( ph 7.4 ) .
for neuronal survival counting and the immunohistochemical evaluation , subjects ( n = 5 for each group ) were fixed by vascular perfusion of 10% formaldehyde in phosphate buffer ( ph 7.4 ) . the lumbar intumescence was dissected out , postfixed overnight , washed in phosphate buffer , and stored in sucrose 10 , 20 , and 30% for 24  h each , before freezing .
transverse cryostat sections ( 12  m thick ) of the lesioned spinal cord segments ( l4 , l5 , and l6 ) were obtained , transferred to gelatin coated slides , and stored at 22c until use . for sciatic nerve regeneration analysis , the rats were transcardially perfused with 200  ml of a fixative containing 2.5% glutaraldehyde and 1.0% paraformaldehyde in 0.1  m phosphate buffer ( ph 7.4 ) . the sciatic nerve ipsi and contralateral to the lesion were removed and stored overnight in the same fixative at 4c .
the specimens were then osmicated , dehydrated , and embedded in durcupan ( fluka acs , steinheim , switzerland ) .
the resin blocks were trimmed and semithin sections ( 0.5  m ) were obtained and stained with 0.7% sudan black in 70% of ethanol solution for morphometric analysis .
counting of motoneurons survival was performed on spinal cord sections ( n = 5 for each group , ipsi and contralateral ventral horn , 4 , 8 , and 12 weeks after lesion ) .
cryostat transverse sections were stained for 35  min in aqueous 1% cresyl fast violet solution at room temperature .
the sections were then washed in distilled water , dehydrated , and mounted with entellan ( merck , darmstadt , germany ) .
the motoneurons were identified based on their morphology and location in the ventral horn ( dorsolateral lamina ix ) .
only cells with visible nucleus were counted for every twentieth section ( totalizing an interval of 240  m between sections ) along the lumbar enlargement , both on the ipsilateral and contralateral sides of each spinal cord .
the percentage of surviving cells was analyzed by the ratio of absolute numbers of motoneurons , counted per section , on the lesioned and nonlesioned sides , respectively , and multiplying the result by 100 .
abercrombie 's formula   was used to correct the duplicate counting of neurons : n = nt/(t + d ) , where n is the corrected number of neurons counted , n is the number of cells counted , t is the thickness of the sections ( 12  m ) , and d is the average diameter of neuronal nuclei . since the difference in size significantly affects cell counts , the value of d was calculated specifically for each experimental group ( ipsilateral and contralateral ) . in this sense ,
the nuclear diameter of 15 randomly picked neurons from each group was measured with imagej software ( version 1.33 , national institutes of health , usa ) and the mean value was calculated .
slides containing transverse spinal cord sections were incubated for 45  min in a 3% bsa solution followed by incubation with the following primary antibodies : mouse anti - synaptophysin ( dako , glostrup , denmark 1  :  200 ) rabbit anti - gfap ( abcam , 1  :  1500 ) , and rabbit anti - iba1 ( waco , 1  :  700 ) .
the primary antibodies were diluted in a solution containing 1% bsa ( bovine serum albumin ) and
all sections were incubated for three hours in a moist chamber at room temperature . after rinsing in pb
, the sections were incubated with a cy3-conjugated secondary antiserum ( 1  :  250 , jackson immunoresearch , west grove , pa , usa ) for 45  min in a moist chamber at room temperature .
the sections were then rinsed in pb , mounted in a mixture of glycerol / pb ( 3  :  1 ) , and observed with a leica dm5500b microscope coupled with a leica dfc345 fx camera . for quantitative measurements ,
three representative images of the ipsilateral and contralateral ventral horn were captured from each animal for all experimental groups ( n = 5 for each group , ipsi and contralateral ventral horn , 4 , 8 , and 12 weeks after lesion ) . for analysis of synaptophysin immunolabeling ,
the integrated density of pixels was measured in eight areas surrounding each lateral motor nucleus motoneuron , in the anterior horn of the spinal cord . for the analysis of anti - glial fibrillary acidic protein ( gfap ) and anti - ionized calcium binding adaptor molecule 1 ( iba1 )
antibodies , the integrated density of pixels was measured in the lateral region of the spinal cord ventral horn , as described by oliveira et al . and freria et al .
the integrated density of pixels was calculated for each section and then as a mean value for each spinal cord .
the data are represented as the mean  standard error ( se ) for each group .
morphometry , regenerated axon area , and counting analyses were performed by sampling at least 30% of each nerve cross - section ( magnification of 1,000x ) using a bright field microscope ( n = 5 for each group , ipsi and contralateral ventral horn , 4 , 8 , and 12 weeks after lesion ) .
sampling bias was avoided by spreading the micrographs systematically over the entire cross - section , according to the procedure proposed by mayhew and sharma .
these images were used for counting the total number of myelinated fibers . for each specimen ,
two fields were used to measure the perimeter and diameter of myelinated fibers and the myelin area , using adobe photoshop cs6 extended .
these values were used to calculate the myelinated axon diameter , fiber diameter , myelin thickness ( fiber diameter , axon diameter/2 ) , and  g  ratio ( axon diameter / fiber diameter ) that indicate the relative success of the regeneration process as well as myelination process .
lumbar spinal cords ( n = 3 for each group , ipsi and contralateral ventral horn , 4 weeks after lesion ) were dissected out and stored overnight in fixative at 4c .
the specimens were then trimmed , osmicated , dehydrated , and embedded in durcupan ( fluka ) .
ultrathin sections from the l4l6 segments were collected on formvar coated copper grids , counterstained with 2% uranyl acetate and lead citrate , and examined under a transmission electron microscope operating at 120  kv ( tecnai biotwin g2 spirit , fei company , the netherlands ) .
neurons with large cell bodies ( ~35  m in diameter ) , found in the sciatic motoneuron pool and cut in the nuclear plane , were identified as -motoneurons by the presence of c - type nerve terminals and chromatolysis ( axotomized side ) .
the cell surfaces were then sequentially digitalized at a magnification of 11,000x with an eagle 2k video camera ( fei company , the netherlands ) connected to a computer system , and the images mounted together using vector graphics software .
synaptic terminals opposing the motoneuron somata were identified and their numbers per 100  m of cell membrane , as well as the membrane covering of all the terminals ( calculated in percentage of membrane length ) , were determined using the measurement tool of image j software ( version 1.33u , national institutes of health ( nih ) , usa ) .
the terminals were typed as f - type ( flattened synaptic vesicles or flattened and spherical vesicles that contain glycine / gamma - aminobutyric acid ( gaba ) as neurotransmitter ) , s - type ( spherical synaptic vesicles that contain glutamate as the neurotransmitter ) , or c - type ( presence of a subsynaptic cistern and acetylcholine as the neurotransmitter ) , according to the procedure described by conradi in 1969   ( supplementary figure s2 ) . the distance between consecutive nerve terminals covering the motoneurons
a total of 24 sciatic -motoneurons from three animals per group ( two neurons per animal in four groups , ax , ax+fs , ax+cfs , and contralateral ) were quantified .
motor function was analyzed using the peroneal functional index ( pfi ) by the walking track test ( catwalk system , noldus inc .
a high speed video camera gevicam ( gp-3360 , usa ) equipped with a wide - angle lens ( 8.5  mm , fujicon corp . ,
china ) is positioned underneath the walkway and the paw prints are automatically recorded and classified by the software .
the paw prints from each animal were obtained twice a week from the third week of life .
pfi was calculated as the distance between the third toe and hind limb pads ( print length ) and the distance between the first and fifth toes ( print width ) .
measurements of these parameters were obtained from the right ( unlesioned ) and left ( lesioned ) paw prints , and the values were calculated using the following formula described by bain and colleagues in 1989 : ( 1)pfi=174.9eplnplnpl+80.3etsntsnts13.4,where n : normal or nonoperated side ; e : experimental or operated ; pl : print length ; ts : total toe spread , or distance between first to fifth toes .
, ribeiro preto , sp , brazil ) was utilized to evaluate sensory function recovery ( n = 5 for each group ) .
for that , the rats were kept inside acrylic boxes for twenty minutes before the experiment for habituation .
nociception threshold was measured at the plantar region by touching the skin with a pipette tip adapted to a force transducer , which is connected to a digital counter that shows the force , in grams , used to trigger the paw flinch .
hyperalgesia was measured by stimulating the paw surface for six times , and the results were averaged and shown as a mean  se . in order to avoid foot pad lesion and inflammation , the maximum stimulation weight ( cut - off threshold ) was set to 70  g. each data collection was carried out in duplicate and in a blinded manner .
the data are presented as mean  se , and the differences between groups were considered significant when the p value was < 0.05 (  ) , < 0.01 (  ) , and < 0.001 (  ) . statistical analysis was performed with graphpad prism 4.0 software . in this sense , data were subjected to anova followed by bonferroni post hoc test for parametric data or mann - whitney u test for nonparametric data .
neuronal survival was investigated as the ipsi / contralateral ratio of motoneurons present at ventral horn lamina ix .
after 4 , 8 , and 12 weeks , a severe degeneration motoneuron was observed in the ax group .
coaptation groups performed equally well and presented statistically significant rescue of axotomized motoneurons ( figure 1 , table s1 ) .
no significant differences between the numbers of motoneurons on the contralateral side in the different experimental conditions were observed .
additionally , axotomy alone with immediate reapposition of the stumps and followed by 2  mm proximal stump resection did not differ with regard to motoneuron survival ( supplementary figure s3 ) .
quantitative measurements of synaptophysin immunoreactivity in the sciatic motor nuclei after axotomy ( ax ) and after axotomy followed by coaptation ( ax+fs ; ax+cfs ) were carried out 4 , 8 , and 12 weeks after injury .
axotomy group showed significant reduction of immunoreactivity ipsilateral to the lesion side . on the contrary , synaptic covering
was preserved following coaptation in all survival times analyzed ( figure 2 , supplementary data table s2 ) . a significant increase in astrocyte reactivity after axotomy
was observed four weeks after lesion ( figure 3 , supplementary data table s3 ) .
similar results were observed in microglial reactivity , where groups with coaptation showed decreased microglial reaction , particularly at four weeks after lesion ( figure 4 , supplementary data table s4 ) .
although absence of spontaneous regeneration following axotomy alone was observed , acute coaptation ( ax+fs , ax+cfs ) resulted in axonal growth with sensorimotor recovery .
area measurements showed no significant difference between ax+fs and ax+cfs groups , although such nerves presented reduced dimensions as compared to the contralateral ( nonlesioned ) samples ( table 1 ) .
additionally , the estimation of total number of axons revealed no significant differences between coaptation groups ( figure 5 , supplementary data table s5 ) , although significantly reduced in comparison to the normal nerve .
of note , commercial fibrin adhesive displayed the worst values for all parameters analyzed at four weeks after lesion , indicating slower axonal regeneration progress ( figures 6 , 7 , and 8) .
such initial difference was not present eight and twelve weeks after lesion , so that both coaptation groups performed in a similar fashion at later stages .
statistical differences between groups were only observed at four weeks after sciatic nerve coaptation . in this sense , ax+fs displayed better recovery as compared to ax+cfs .
such statistical evaluation is presented in detail as supplementary material : figure s4 , fiber diameter ; figure s5 , axon diameter ; and figure s6 , myelin thickness .
no statistical differences were depicted regarding the  g  ratio ( figure 9 ) , although cfs group presented mostly under myelinated fibers four weeks after injury .
all analyzed motoneurons showed at least one cholinergic presynaptic terminal ( type c ) in apposition to the plasmatic membrane surface .
lesioned neurons , affected by axotomy , showed changes compatible with chromatolysis , such as displacement of the nucleus to the periphery and decrease in cytoplasm electron density .
glial projections were observed , in the ax group , intermingling the space between part of the presynaptic terminals and the postsynaptic membrane ( figure 10(a ) ) .
fully apposed terminals were depicted in the other experimental groups ( figures 10(b)10(d ) ) .
the total synaptic covering , which represents the motoneuron body surface in contact with presynaptic terminals , revealed reduction of excitatory terminal covering in all groups analyzed , when compared to the contralateral side ( figure 10(e ) ) .
four weeks after lesion , nontreated neurotmesis ( ax group ) , presented a 41.22% covering reduction of type s inputs when compared with contralateral side .
nerve coaptation resulted in excitatory input preservation , with no statistical differences between commercial and cevap sealant ( figures 10(f ) and 10(g ) ) .
fibrin sealant nerve repair promoted even more prominent effects on inhibitory inputs ( type f boutons ) , showing close to normal covering ( figures 10(f ) and 10(g ) ) .
axotomy alone led to greater distance between terminals that contrasted with coaptation repair , where clusters of terminals were close to each other ( figures 10(h)10(k ) ) .
the recovery of motor function was studied by the walking track test , using the catwalk system ( noldus inc . ) .
statistical analysis from peroneal functional index showed a significantly greater peroneal functional index ( pfi ) following coaptation ( ax+fs , ax+cfs ) , regardless the nature of the fibrin sealant ( figure 11 ) .
pfi has been chosen over sciatic functional index ( sfi ) , because measuring the intermediate toe spread ( its ) was not possible .
we regard that to muscle atrophy since nerve lesion was performed in the neonatal period .
the nociceptive recovery was analyzed by stimulation of the plantar surface of the paw with electronic von frey .
contralateral paw showed withdraw reflex around 30  g. axotomy alone ( ax ) rats did not show withdraw behavior at the cut - off weight , indicating lack of sensory perception ( 70  g , figure 12(a ) ) .
both groups subjected to coaptation with fibrin sealant ( ax+fs and ax+cfs ) showed lower threshold withdrawal response ( around 45  g , figures 12(b)-12(c ) ) .
it is well known that neonatal axotomy results in devastating neuronal loss in the spinal cord and dorsal root ganglia ( drg ) .
this is particularly because of the interruption of neurotrophic factors production and retrograde flow , mostly at the target organs .
in fact , administration of neurotrophic factors , such as brain derived neurotrophic factor ( bdnf ) and ciliary neurotrophic factor ( cntf ) rescue motoneurons from degeneration . also , the use of cannabidiol ( cbd ) , a cannabinoid with neuroprotective properties , is also able to avoid both motoneuron and drg neurons death , following neonatal peripheral nerve lesion . in this way
, early neonatal nerve axotomy has been broadly accepted as a consistent model for studying neuroprotection [ 46 , 48 ] .
nevertheless , due to the reduced size of pups , combined with the thin and delicate structure of the peripheral nerves at perinatal stage , repair following transection is hardly accomplishable .
the present work shows that end - to - end nerve coaptation can be performed in a reproducible fashion by using fibrin sealant as a connecting structure between proximal and distal stump .
it is important to highlight that in humans nerve size is larger , allowing direct suturing . in this scenario ,
the use of fibrin glue may enhance repair stability and function as a scaffold for cell migration . in the present study
, we compared two different fibrin adhesives , one commercial brand and another recently developed by cevap .
the latest is based on nonhuman components , avoiding transmission of infectious blood - borne diseases .
the results have shown that both sealants ( commercial and cevap ) are excellent for the coaptation process , although cevap 's fibrin sealant has proven to be easier to handle at the moment of surgery .
surgeries involving neonatal subjects ought to be particularly fast , and clotting speed is a crucial parameter . due to the fact that cevap derived adhesive uses bubaline fibrinogen , the concentration of such protein in the cryoprecipitate is specially higher than the human counterpart . in turn
this in turn possibly allowed early regrowth of regenerating axons , originated from the proximal stump , resulting in improved morphometric parameters , four weeks after repair . in line with the positive results described in the present work , the fibrin sealant from cevap has been tested in humans , for autologous skin grafting of the nasogenian sulcus showing promising results .
moreover , it has been tested for the immobilization of free periodontal gingival grafts in lower premolars and for the treatment of chronic venous ulcers [ 5054 ] .
besides , recent studies also show the efficacy of this new sealant on peripheral nerve regeneration [ 55 , 56 ] , treatment of skull defects , and following ventral root avulsion .
it has been shown that this scenario can be partially reversed by local or systemic administration of trophic substances , such as neurotrophins , antioxidants , cannabinoids , and gangliosides [ 47 , 59 , 60 ] .
nevertheless , the regrowth of axons from the spinal motoneurons and drg neurons towards the periphery is dependent on anatomical restauration of pns structures .
we show that coaptation at the neonatal stage is neuroprotective by itself and generates a permissive scaffold through which regeneration can be successfully accomplished .
the results shown herein indicate significant preservation of motoneurons in the spinal cord , assessed by direct counting at 4 , 8 , and 12 weeks after lesion , reinforcing the long lasting positive effects of the repair procedure .
nevertheless , since nerve repair was carried out at p2 , motor and sensory evaluation could only be initiated from the third ( catwalk ) or fourth ( von frey ) week of age due to animal size and sensory - motor coordination . in turn ,
our data reflect already established recovery that happened before behavior tests could be started , what explains the rather constant peroneal and von frey results .
importantly , restauration of neonatal lesion , which mimics obstetric brachial plexus injury , led to preservation of synapses , as seen by synaptophysin immunostaining .
reduction of astrogliosis and microglial reaction also contribute to synapse stability and functionality , correlating with substantial motor and sensory recovery in ax+fs and ax+cfs groups up to twelve weeks after surgery . in this regard ,
improved peroneal index following coaptation was observed with either fibrin sealant treatment , when compared with axotomy alone .
such improvement indicates reestablishment of muscle innervation as well as suprasegmental control [ 61 , 62 ] .
after an injury , retraction of presynaptic boutons that appose spinal motoneurons takes place during the first week after lesion .
this event reduces synaptic transmission [ 6469 ] and allows the axotomized neurons to focus metabolism on survival and regrowth of a new axon and dendrites .
herein , synaptic covering was significantly preserved in coaptation groups , in line with the immunohistochemical observations ( synaptophysin ) .
a quantitative analysis of the synaptic covering for each type of presynaptic terminal showed significant preservation of s and f type of synapses .
however , the proportion of preserved inhibitory synapses was greater than excitatory . such scenario , according to lind et al . , facilitates neuroprotection by reducing glutamatergic excitotoxicity [ 70 , 71 ] . besides the prevention of excitotoxicity , the number of preserved presynaptic terminals/100  m in apposition to the alpha - motoneuron membrane was also increased in both coaptation groups .
synapse dynamics also depend on astrocytes and microglia that act in favor of maintenance of homeostasis that is necessary to transmission and synaptic plasticity .
one well - known retrograde effect of peripheral axotomy is the development of central astrogliosis and microglial reaction , directly interfering on synapse stability [ 7275 ] .
gfap and iba1 are highly expressed proteins in astrocytes and microglia , respectively , and are upregulated after lesion [ 73 , 76 ] . the fact that coaptation downregulates glial reaction at lumbar spinal cord level is in line with the positive anatomical and behavioral findings previously discussed .
overall , the present data suggest that acute repair of neonatal peripheral nerve with both fibrin sealant analyzed , namely , a commercial brand and a nonhuman derived adhesive produced by cevap / brazil , promotes neuroprotection and regeneration of motor and sensory axons .
also , the present study demonstrates that neonatal end - to - end nerve coaptation is feasible and may in turn be of use for repairing obstetric brachial plexus injuries .
 brachial plexus lesion results in loss of motor and sensory function , being more harmful in the neonate . therefore , this study evaluated neuroprotection and regeneration after neonatal peripheral nerve coaptation with fibrin sealant . 
 thus , p2 neonatal lewis rats were divided into three groups : ax : sciatic nerve axotomy ( sna ) without treatment ; ax+fs : sna followed by end - to - end coaptation with fibrin sealant derived from snake venom ; ax+cfs : sna followed by end - to - end coaptation with commercial fibrin sealant . 
 results were analyzed 4 , 8 , and 12 weeks after lesion . 
 astrogliosis , microglial reaction , and synapse preservation were evaluated by immunohistochemistry . 
 neuronal survival , axonal regeneration , and ultrastructural changes at ventral spinal cord were also investigated . 
 sensory - motor recovery was behaviorally studied . 
 coaptation preserved synaptic covering on lesioned motoneurons and led to neuronal survival . 
 reactive gliosis and microglial reaction decreased in the same groups ( ax+fs , ax+cfs ) at 4 weeks . regarding axonal regeneration , coaptation allowed recovery of greater number of myelinated fibers , with improved morphometric parameters . 
 preservation of inhibitory synaptic terminals was accompanied by significant improvement in the motor as well as in the nociceptive recovery . 
 overall , the present data suggest that acute repair of neonatal peripheral nerves with fibrin sealant results in neuroprotection and regeneration of motor and sensory axons . 