Distribution Of Nerve Fibers Research Articles

Distribution and morphological changes of subbasal nerve fiber after different excimer laser operation

目的 观察准分子激光原位角膜磨镶术(LASIK)和准分子激光上皮下角膜磨镶术(LASEK)术后角膜上皮基底膜下神经分布及形态学特征.方法 共焦显微镜观察低、中度近视LASIK及LASEK 27例(54眼),术前、术后1、3、6月的角膜上皮基底膜下神经纤维分布和形态学特征,并测定泪膜破裂时间(BUT)和泪液分泌量(Schirmer I值).结果 LASIK(12例,24眼)与LASEK(15例,30眼)术后角膜上皮基底膜下神经纤维的再生和形态学在各时间点差异均无统计学意义.两组中BUT有统计学意义(P 0.05).结论 对于低、中度近视而言,LASIK与LASEK术后角膜上皮基底膜下神经纤维的再生未显示形态学上的差异。

Recovery process of sciatic nerve defect with novel bioabsorbable collagen tubes packed with collagen filaments in dogs

Autologous nerve graft is the most commonly applied treatment for the patients with peripheral nerve defect, while application is limited because of tissue availability and unfavorable donor site morbidity. To overcome this problem, peripheral nerve regeneration using a nerve conduit has been studied. Especially, nerve conduit using biodegradable materials has been considered promising. In this study, a potential of collagen nerve conduit has been studied with special reference to the regenerating process of a peripheral nerve. Twelve adult female Beagle dogs weighting 10-12 kg were used. The peroneal nerve was cut to make a 30-mm defect. The nerve defect was bridged by the collagen artificial nerve conduit. Comprehensive functional, electrophysiological, morphometrical, and histological analyses were performed until one year after operation. The wet weight of tibialis anterior muscles was only 32.4% of the healthy side at 24 weeks, which was recovered to 77.4% at 52 weeks after denervation. Electrophysiological evaluation of tibialis anterior muscle belly showed polyphasic wave at 52 weeks after implantation, which was almost half amplitude as compared with that of control. The diameters of myelinated nerve fibers thickened day by day, and the average diameter was 5.16 microm at PFN, 3.91 microm at CG, and 3.75 microm at DFN, and average thickness of myelin sheath was 0.94 microm at PFN, 0.46 microm at CG, and 0.55 microm at DFN after 52 weeks. The distribution of myelinated nerve fiber size in the 52 weeks group was distinctly bimodal with the major peak at approximately 2-4 microm and the minor peak at 10-12 microm. These findings were consistent with the distribution of the normal nerve fiber. This study proves the feasibility of the collagen artificial nerve conduit for promoting nerve regeneration, raises new possibilities of seeking alternatives to autograft for nerve repair. The results from this study showed detailed process of morphological, electrophysiological, and functional recovery of the regenerated nerve, which would provide scientific background for this novel therapy.

Noradrenergic parenchymal nerve fiber branching after cold acclimatisation correlates with brown adipocyte density in mouse adipose organ

The mammalian adipose organ is composed of subcutaneous and visceral depots containing white and brown adipocytes. Cold acclimatisation induces an increase in the brown component without affecting the overall number of adipocytes; this form of plasticity is associated to obesity and diabetes resistance in experimental models. Cold activates the drive of the sympathetic nervous system to the adipose organ, where the vast majority of nerve fibers are in fact noradrenergic. However, it is unclear whether and how such fibers are involved in the plastic changes of the adipose organ. We thus conducted a systematic study of the distribution and number of sympathetic noradrenergic nerve fibers in the adipose organ of mice kept at different environmental temperatures. Adult Sv129 female mice were kept at 28 degrees C or 6 degrees C for 10 days. The density of tyrosine hydroxylase (noradrenergic)-positive nerve fibers (no. of fibers per 100 adipocytes) was calculated in the subcutaneous and visceral depots of the adipose organ, and a correlation was sought between fiber density and proportion of brown adipocytes. Tyrosine hydroxylase-positive parenchymal fibers were detected in all subcutaneous and visceral depots among white as well as brown adipocytes, the mediastinal depot displaying the densest innervation. Cold acclimatisation induced a threefold increase in the total number of TH fibers in the whole organ. The proportion of brown adipocytes positively correlated with noradrenergic fiber density in the organ. Taken together, these data suggest that cold acclimatisation induces noradrenergic fiber branching in the adipose organ of adult mice, and that such changes may be a precondition for its plastic transformation into a brown phenotype.

Lead placement and associated nerve distribution of an implantable periurethral electrostimulator

The aim of this study was to determine gross and neuroanatomic features of a novel periurethral neuromuscular electrostimulator. Periurethral leads were placed in eight female cadavers. In two cases, leads were imaged after placement to enhance anatomic understanding. Pelvic viscera were removed en bloc for analysis of lead placement in the six remaining cadavers. Excised tissue was sectioned and immunostained to identify general, afferent, sympathetic, and nitric oxide synthase efferent nerve fibers. The electrodes were found within/lateral (n = 4), within/posterolateral (n = 9), and anterolateral (n = 1) to the external urethral sphincter (distance 0.25 +/- 0.5, 2.9 +/- 3.3, and 1.0 +/- 0.0 mm, respectively). The electrode to the urethra and vagina distance averaged 7.6 +/- 3.4 and 8.8 +/- 4.3 mm, respectively. Variable density staining for all nerve types was found around the electrode. A periurethral electrode interfaces the external urethral sphincter, and the adjacent distribution of nerve fibers supports proposed neuromuscular therapeutic mechanisms.

Decreased nerve distribution in mixed venous-lymphatic malformation

In order to investigate the nerve distribution in mixed venous-lymphatic malformations (MVLMs), 57 postoperative patients diagnosed with MVLMs of the tongue were selected. Immunohistochemistry staining for neurofilament (NF) was used to detect sensory nerve fibers. Distribution of NF in samples from MVLMs was compared with distribution of NF in normal tongue tissue, venous malformations, lymphatic malformations and venular malformations. Results showed that the number of NF-positive nerve fibers in MVLMs was comparable to that in venous malformations and lymphatic malformations. The number of nerve fibers in MVLMs was significantly lower than in normal tissues. NF distribution in MVLMs was not affected by the patient’s age or the coexistence of infection. These data suggest that the decreased distribution of sensory nerve fibers in MVLMs may be involved in the pathogenesis of MVLM of the tongue.

An immunohistochemical study of ovarian innervation in the emu (<i>Dromaius novaehollandiae</i>)

The present study investigated the distribution of nerves in the ovary of the emu. The neuronal markers, protein gene product 9.5, neurofilament protein and neuron specific enolase demonstrated the constituents of the extrinsic and intrinsic ovarian neural systems. The extrinsic neural system was composed of ganglia in the ovarian stalk, as well as nerve bundles, which were distributed throughout the ovary. Isolated neuronal cell bodies, in the medulla and cortex, formed the intrinsic neural system. An interesting finding of the study was the presence of nerve bundles, circumscribed by lymphocytes, in the ovarian stalk. The findings of the study indicate that the distribution of nerve fibres and neuronal cell bodies in the emu ovary is similar, but not identical to that of the domestic fowl and ostrich.

Effects of angiotensin converting enzyme inhibition on cardiac innervation and ventricular arrhythmias after myocardial infarction

To investigate the influence of angiotensin-converting enzyme inhibitor (ACEI) on cardiac innervation and inducible ventricular arrhythmias (VAs) in healed myocardial infarction (MI). Left anterior descending coronary artery was ligated to induce MI in 30 rabbits. After oral captopril (10mg/kg/d) for 8 weeks, electrophysiological study was performed to evaluate the incidence of inducible VAs. RT-PCR and immunohistochemistry were used to measure the cardiac innervation. Eight weeks after the operation, the incidence of inducible VAs in the MI-placebo group was higher (58.3%, 7/12) than in the sham operation group (16.7%, 2/12, P < 0.05). However, the incidence of inducible VAs in the MI-captopril group was lower (27.2%, 3/11) than in the MI-placebo group (P < 0.05). Proliferation and growth of nerve fibres in the MI-placebo group were mainly distributed at the periphery of the infarcted and perivascular regions of the myocardium. The density of nerve fibres increased in the MI-placebo group (3889+/-521 microm2/mm2) compared with the sham group (1727+/-304 microm2/mm2, P < 0.01) at the infarct border. In the MI-captopril group, the density of nerve fibres (3507+/-433 microm2/mm2) at the infarct border did not differ from that in the MI-placebo group (P=0.07). MI-induced abnormal nerve fibre distribution was partly restored by captopril treatment. In this study, prolonged captopril treatment was effective in preventing VAs in healed MI, partly by attenuating the spatial heterogeneity of cardiac innervation.

Histopathologic Study of the Neuroma-in-Continuity in Obstetric Brachial Plexus Palsy

Operative treatment of traction lesions in obstetric brachial plexus palsy is still controversial. The authors analyzed the histopathology of neuroma-in-continuity of the upper trunk by study of the resected neuroma. The neuroma-in-continuity of the upper trunk was studied histopathologically in 28 children with Erb palsy who had undergone resection of the neuroma and nerve reconstruction of the plexus at the age of 3 to 11 months. The authors recorded the distribution of myelinated motor nerve fibers and the proportions of collagen and regenerating nerve fibers traveling the neuroma, analyzed the relationship between the percentage of nerve fibers across the neuroma and findings of intraoperative neurophysiologic investigations and the patient's age at surgery, and compared the number of nerve fibers in C5 and C6 proximal to the neuroma with that in their normal counterparts. In the central segment of the neuroma, the structure of the upper trunk was replaced by copious collagen and sporadic nerve fibers wrapped by an undeveloped myelin sheath, and the percentage of collagen was statistically greater than that of the normal upper trunk. The mean percentage of regenerating nerve fibers across the neuroma was 41.83 percent (95 percent confidence interval, 38.69 to 44.69 percent) and this was not statistically correlated with the outcome of intraoperative neurophysiologic investigations or the patient's age at surgery. The number of nerve fibers was statistically less in C5 and C6 proximal to the neuroma than in their normal counterparts. The nerve structure of the neuroma-in-continuity is substantially damaged in obstetric brachial plexus palsy. Its resection followed by nerve reconstruction of the plexus is favored.

Chronological Change in Intramural Components in Severe Proximally Dilated Jejunal Atresia: An Immunohistochemical Study

Chronological Change in Intramural Components in Severe Proximally Dilated Jejunal Atresia: An Immunohistochemical Study

Deafferentiation‐associated changes in afferent and efferent processes in the guinea pig cochlea and afferent regeneration with chronic intrascalar brain‐derived neurotrophic factor and acidic fibroblast growth factor

Deafferentation of the auditory nerve from loss of sensory cells is associated with degeneration of nerve fibers and spiral ganglion neurons (SGN). SGN survival following deafferentation can be enhanced by application of neurotrophic factors (NTF), and NTF can induce the regrowth of SGN peripheral processes. Cochlear prostheses could provide targets for regrowth of afferent peripheral processes, enhancing neural integration of the implant, decreasing stimulation thresholds, and increasing specificity of stimulation. The present study analyzed distribution of afferent and efferent nerve fibers following deafness in guinea pigs using specific markers (parvalbumin for afferents, synaptophysin for efferent fibers) and the effect of brain derived neurotrophic factor (BDNF) in combination with acidic fibroblast growth factor (aFGF). Immediate treatment following deafness was compared with 3-week-delayed NTF treatment. Histology of the cochlea with immunohistochemical techniques allowed quantitative analysis of neuron and axonal changes. Effects of NTF were assessed at the light and electron microscopic levels. Chronic BDNF/aFGF resulted in a significantly increased number of afferent peripheral processes in both immediate- and delayed-treatment groups. Outgrowth of afferent nerve fibers into the scala tympani were observed, and SGN densities were found to be higher than in normal hearing animals. These new SGN might have developed from endogenous progenitor/stem cells, recently reported in human and mouse cochlea, under these experimental conditions of deafferentation-induced stress and NTF treatment. NTF treatment provided no enhanced maintenance of efferent fibers, although some synaptophysin-positive fibers were detected at atypical sites, suggesting some sprouting of efferent fibers.

Coenzyme Q(10) and alpha-lipoic acid supplementation in diabetic rats: Conduction velocity distributions

Diabetic neuropathies are a family of nerve disorders caused by diabetes. Patients with diabetes can develop nerve problems at any time, but the longer a person has diabetes the greater the risk. This study aims to investigate diabetes- and coenzyme Q(10) (CoQ(10)) or alpha-lipoic acid (ALA) supplementation-induced changes in the conduction velocity (CV) distributions of rat sciatic nerve fibers. Sciatic nerve compound action potentials (CAPs) were recorded by suction electrode and CV distributions by the collision technique. Diabetes resulted in a significant increase in time to peak, rheobase and chronaxie values of these CAP waveforms, whereas the maximum depolarization, area, kinetics and CVs of both fast and slow nerve fiber groups were found to be decreased. Coenzyme Q(10) (CoQ(10)) supplementation was found to have some positive effect on the diabetes-induced alterations. CoQ(10) supplementation induced positive changes mainly in the area and fall-down phase of the kinetics of CAP waveforms, as well as rheobase, chronaxie and speed of the intermediately conducting groups ( approximately or equal to 40 m/s). alpha-Lipoic acid (ALA) supplementation did not produce statistically significant effects. This study has shown for the first time that diabetes induces a shift of actively contributing nerve fibers toward slower CVs, and supplementation with CoQ(10) not only stopped this shift but also tended to restore velocities toward those of the age-matched control group. In addition to its effects on mitochondrial alterations, these positive effects of CoQ10 on diabetic neuropathy can be attributed to its antioxidant activity.

Neurokinin 1 receptor, IB4 lectin and nitric oxide synthase localizations in whole-mount preparation of the rat meninges following noxious stimulation

Distribution and immunocytochemical characterization of the nerve fibers and their terminals in Wistar rats (n=15) meninges were studied by using neurokinin 1 receptor, IB4 lectin and nitric oxide synthase labeling after the application of noxious peripheral stimulation. For immunocytochemistry, free floating specimens were incubated with neurokinin 1 receptor, nitric oxide synthase and IB4 lectin antibodies and then observed with avidin-biotin-peroxidase method. The neuronal markers stained in all unmyelinated nerve fibres throughout the meninges. Neurokinin 1 receptor- and IB4 lectinimmunoreactive nerve fibers were localized in all leptomeningeal compartments, where they terminated close to the subarachnoid space or within the connective tissue, thus suggesting extensive distribution of nerve fibres in the meninges. Neuronal nitric oxide synthase-positive nerve fibers and a prominent mast cell population were seen in the rat leptomeninx and dura. The presence of a significant number of putative nociceptive fibres suggests a possible role for nociceptive function in the context of pathophysiological aspects. The distributions pattern of IB4 lectin binding sites, neurokinin 1 receptor and nitric oxide synthase could be due to the function of particular segments in the pathogenesis of meningeal vascular network.

Intercellular Communication Within the Rat Anterior Pituitary: XIV Electron Microscopic and Immunohistochemical Study on the Relationship Between the Agranular Cells and GnRH Neurons in the Dorsal Pars Tuberalis of the Pituitary Gland

Although numerous investigators in 1970s to 1980s have reported the distribution of LH-RH nerve fibers in the median eminence, a few LH-RH fibers have been shown to be present in the pars tuberalis. The significance of the finding remains to be elucidated, and there are few studies on the distribution of LH-RH neurons in the pars tuberalis, especially in the dorsal pars tuberalis (DPT). Adult male Wistar-Imamichi rats were separated into two groups: one for electron microscopy and the other for immunohistochemistry to observe LH-RH and neurofilaments. Pituitary glands attached to the brain were fixed by perfusion, and the sections were prepared parallel to the sagittal plane. The typical glandular structure of the pars tuberalis was evident beneath the bottom floor of the third ventricle, and the thick glandular structure was present in the foremost region. Closer to the anterior lobe, the glandular structure changed to be a thin layer, and it was again observed at the posterior portion. Then the pituitary stalk was surrounded with the dorsal, lateral, and ventral pars tuberalis. LH-RH and neurofilaments fibers were noted in the bottom floor, and some of them vertically descended to the gland. Adjacent to the glandular folliculostellate cells in the pars tuberalis, Herring bodies with numerous dense granules invading into the gland were present between the pituitary stalk and DPT. It was postulated that the "message" carried by LH-RH might have been transmitted to the cells in the DPT to aid in the modulation of LH release.

Are Natural Killer Cells Distributed in Relationship to Nerve Fibers in the Pregnant Mouse Uterus?

Specialized lymphocytes, called uterine Natural Killer (uNK) cells, appear in human and rodent uteri and become abundant at implantation sites during decidualization and early pregnancy. The hallmark of human uNK cells is intense expression of CD56, a neural cell adhesion glycoprotein (NCAM-1) while mature (granulated) mouse uNK cells express asialoGM1, a brain ganglioside. Murine uNK cells initiate the normal structural changes induced in maternal spiral arteries by pregnancy but regulation of their recruitment, localization and activation is incompletely understood. To address whether uNK cell distribution is co-localized with nerve fiber distribution, sections of gestation day (gd) 6-12 implantation sites from C57BL/6 (B6) mice were studied. Nerve fibers reactive with antibodies to pan neurofilament 150 kD or with tyrosine hydroxylase, an enzyme restricted to sympathetic fibers, were present the walls of branches from the uterine artery in the mesentery. Reactivity was lost as the vessels crossed the myometrium and entered endometrium/decidua. Periodic Acid Schiffs reactive uNK cells were absent from the mesentery and enriched in decidua basalis where they transcribed NCAM-1 and associated with non-innervated segments of the uterine arteries, including spiral arteries. These data suggest that the localization and activation of mature uNK cells are unlikely to be neurotransmitter regulated.

Distribution and origin of TRPV1 receptor-containing nerve fibers in the dura mater of rat

We examined the distribution and origin of the nerve fibers innervating the dura mater of the rat that show immunoreactivity for the TRPV1 receptor (TRPV1-IR). Nearly 70% of the nerve fibers showing TRPV1-IR in the dura mater also exhibited CGRP-IR. Using a combination of immunohistochemistry and a retrograde tracer technique, we detected tracer accumulation in 0.6% of the neurons in the trigeminal ganglion and a few neurons in the dorsal root ganglion; half of the neurons in the trigeminal ganglion were small- and medium-sized (≤ 1000 μm 2). Among the tracer-accumulated neurons in the trigeminal ganglion, approximately 25% exhibited TRPV1-IR. Furthermore, nearly 80% of the tracer-accumulated small- and medium-sized neurons in the trigeminal ganglion that exhibited TRPV1-IR also exhibited CGRP-IR. Our findings indicate that the TRPV1 receptor in the dura mater and sensory ganglia may contribute to the pathophysiology of migraine, providing an important clue for the development of therapeutic strategies for migraine.

Substance P and its receptors in bone metabolism

Accumulating evidence on bone physiopathology has indicated that the skeleton contains numerous nerve fibers and its metabolism is regulated by the nervous system. Until now, more than 10 neuropeptides have been identified in bone. Substance P (SP) is a neuropeptide released from axons of sensory neurons, belongs to the tachykinin family and plays important roles in many physiological and pathological processes by acting as a neurotransmitter, neuromodulator, or trophic factor. It activates signal transduction cascades by acting on the neurokinin-1 receptor (NK(1)-R). Previous studies have confirmed that the SP-immunoreactive (IR) axons innervate bone and adjacent tissues, and that their density varies depending on the regions and physiological or pathological conditions. Over the past few decades, it has been found that SP takes part in the stimulation of bone resorption, and its receptors have been demonstrated to be located in osteoclasts. Notably, in studies of skeletal ontogeny, SP-IR axons have been shown to appear at an early stage, mostly coinciding with the sequence of long bone mineralization. These findings, together with data obtained from chemically or surgically targeted nerve deletions, strongly suggest that SP is a potent regulator of skeletal physiology. The specific distribution of SP-IR nerve fibers, the different amount of SP within regions, and the various levels of expression of NK(1)-R in targeted cells presumably related to and participate in bone metabolism. It can be predicted that the indirect roles of SP through other cytokines are as important as its direct roles in bone metabolism. This new regulating pathway of bone metabolism would have enormous implications in skeletal physiology and the relevant research might present curative potentials to a spectrum of bone diseases.

Intraepidermal nerve fibers increase in dry skin of acetone-treated mice

Skin dryness is apparent in several pruritic skin diseases, such as xerosis and atopic dermatitis. Our previous study has demonstrated an increase of nerve fibers in the epidermis of patients with xerosis, suggesting the contribution of nerve fibers to itching. This study was conducted to reveal a direct linkage between dry skin and intraepidermal nerve growth. ICR mice treated with acetone were used as a dry skin model. Time-dependent measurement of transepidermal water loss (TEWL) and stratum corneum (SC) hydration was performed on the treated areas. Moreover, both the distribution of intraepidermal nerve fibers and the expression of epidermal nerve growth factor (NGF) and amphiregulin (AR) were examined sequentially with immunohistochemistry and quantitative RT-PCR. The same experiments were carried out in control mice treated with sterile water. Enhanced TEWL and decreased SC hydration were observed in the acetone-treated skins during the first hour after the treatment. These parameters gradually returned to the normal range within 48 h. In the acetone-treated mice, we found that there were many nerve fibers in the epidermis between 16 and 48 h after the treatment. No changes of the parameters for barrier disruption and intraepidermal nerve growth were observed in the control skins. Moreover, the expression of epidermal NGF and AR at the protein and mRNA levels was increased before the penetration of nerve fibers into the epidermis. These results suggest that increases of epidermal NGF and AR levels are associated with intraepidermal nerve growth in acetone-treated mice.

Positional relationship between natural killer cells and distribution of sympathetic nerves in decidualized mouse uterus.

Uterine natural killer (uNK) cells are the most abundant leukocytes in pre-implantation endometrium and early pregnancy deciduas in humans and rodents. They are associated with structural changes in maternal spiral arteries but regulation of their recruitment and activation is incompletely understood. The major subpopulation of uNK cells in humans expresses CD56, the neural cell adhesion molecule (NCAM)-1 while their counterpart in mouse expresses asialoGM1, a brain ganglioside. Sympathetic nerves express NCAM-1 which mediates homotypic binding. Sympathetic fibers innervate the mesometrial vasculature but their relationship to the myometrial and decidual uNK cell recruitment is unknown. The present study aims to explore positional relationship between natural killer cells and distribution of nerves in decidualized mouse uterus. Immunohistochemistry and mRNA expression for the enzyme tyrosine hydroxylase were used to map sympathetic nerve fibre distribution within C57BL/6 implantation sites and to address a relationship with uNK cells. Tyrosine hydroxylase positive neurons were identified in the mesometrium closely associated with uterine arteries. Staining became gradually vanished as the nerves crossed the myometrium and entered the decidualized uterus. No neuronal stain was associated with the spiral arteries. Periodic Acid Schiff's reactive uNK cells were absent from the mesentery, but abundant in decidua basalis where they are associated with non-innervated vessels. Data suggest that the recruitment of uNK progenitor cells to the uterus is unlikely to be dependent on signaling by the sympathetic nervous system.

Referred otalgia: a structured approach to diagnosis and treatment

Many patients who present with otalgia have a normal otological examination, and a distant source of pain must be considered. The ear receives an extensive sensory innervation arising from six nerve roots. Many other structures in the head, neck and thorax share a common neuronal pathway with the ear, and these tissues represent the possible sites of disease in the cases of referred otalgia. Consequently, the differential diagnosis is extensive and varied. Making an accurate diagnosis relies on an understanding of the complex distribution of nerve fibres and a structured approach to patient assessment. This article aims to classify the aetiology of referred otalgia and to outline current treatments for these conditions. The origins of referred otalgia may be as remote as the cranial cavity and thorax; however, dental disease, tonsillitis, temporomandibular joint disorders and cervical spine pathology represent the most frequent causes. Ear pain may also be the first sign of a head and neck malignancy. Patients complaining of otalgia, with risk factors for an aerodigestive neoplasm, and a normal ENT examination require an urgent otolaryngological opinion.

Comparative immunohistochemical study of the dopaminergic systems in two inbred mouse strains (C57BL/6J and DBA/2J)

This study investigated possible neurochemical differences in the brain of two inbred mouse strains, C57BL/6J (C57) and DBA/2J (DBA) that in behavioral, memorization and learning tasks under normal and experimental conditions perform differently or often in an opposite manner. The immunohistochemical study, designed to investigate the dopaminergic system, identified many differences within the midbrain A10 area and less marked differences in areas A9 and A8. The number of dopamine transporter (DAT), vesicular monoamine transporter of type 2 (VMT) and tyrosine hydroxylase (TH) immunoreactive cell bodies was significantly higher in the midbrain of DBA mice than in C57 mice (on average +21.5%, P < 0.001 in A10: +9.4% in A9, P < 0.05: and +5.9% in A8, P < 0.1). The distribution patterns of nerve fibres immunoreactive for same antisera also differed significantly in the two strains, especially at prelimbic, infralimbic and anterior cingulate cortical levels. In C57 mice these fibres were scanty whereas in DBA mice they were well represented. In the nucleus accumbens, also the territorial distribution of DAT immunoreactive nerve fibres differed in the two strains. In the midbrain, the galanin immunoreactive axons were more densely distributed in DBA than in C57 mice whereas neurotensin immunoreactive axons were more densely distributed in C57 than in DBA. These distinct immunohistochemical patterns could help to explain why performance differs in the two mouse strains.