Characterization of autonomic nerve markers and lymphocyte subsets in the ileal Peyer's patch of pigs infected experimentally with Brachyspira hyodysenteriae.

The aim of the present study was to investigate potential interrelationships between immune and neural elements of Peyer's patches in normal pigs (n=8) and in pigs infected experimentally with Brachyspira hyodysenteriae and suffering from swine dysentery (n=8). Assessment of tissue concentration of neuropeptides by enzyme linked immunosorbent assay revealed increased levels of galanin (GAL) and substance P (SP) in samples from the infected animals. In contrast, concentrations of vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) were similar in both groups. Immunohistochemistry demonstrated reactivity of nerve fibres with antibodies specific for dopamine ß hydroxylase, vesicular acetylcholine transporter, SOM, GAL, VIP and SP in the interfollicular region and peripheral areas of the Peyer's patch lymphoid follicles. In the dysenteric pigs, the GAL-positive nerve fibres were more numerous and more intensely labelled than those in the normal animals. Flow cytometry revealed a decreased percentage of CD21(+) lymphocytes and lymphocytes expressing T-cell receptor (TCR)-γ, with or without CD8 (TCR-γ(+)CD8(-) and TCR-γ(+)CD8(+)), in the dysenteric pigs as compared with the normal animals. Percentages of other lymphocyte subsets (CD2(+), CD4(+), CD5(+), CD8(+), CD5(-)CD8(+)) were comparable between the groups. Immunohistochemical investigations generally correlated with results obtained by flow cytometry related to lymphocyte subpopulations. Swine dysentery can therefore affect neuroimmunomodulatory processes in the ileal Peyer's patch, in addition to the large intestine. GAL and SP may play a specific role in this neuroimmune cross-talk.

Evidence for coexistence of choline acetyltransferase (ChAT)- and calcitonin gene-related peptide (CGRP)-immunoreactivity in the thoracolumbar and sacral spinal cord neurons of the pig.

Previous immunocytochemical studies provided conflicting data concerning occurrence of the CGRP-immunoreactive neuronal cell bodies in the porcine spinal cord. In the present study, we have investigated expression of the CGRP and its possible coexpression with ChAT in the gray matter of the thoracic, lumbar and sacral spinal cord of the pig. Our study revealed a large number of CGRP-immunoreactive cells in the motor nucleus of the ventral horn, and less and singe perikarya intermediolateral and intermediomedial nuclei, respectively. Double staining immunocytochemistry, depending on the cross-section level, disclosed the highest ChAT/CGRP colocalization subsequently in the motor nucleus of the ventral horn, then in the intermediolateral and intermediomedial nucleus. Our data provide morphological evidence confirming expression of CGRP in the porcine spinal nuclei while its coexpression in cholinergic neurons suggests that CGRP may play a role in modulation of the spinal cholinergic transmission.

Distribution and chemical coding of intramural neurons in the porcine ileum during proliferative enteropathy.

Enteric neurons are highly adaptive in their response to various pathological processes including inflammation, so the aim of this study was to describe the chemical coding of neurons in the ileal intramural ganglia in porcine proliferative enteropathy (PPE). Accordingly, juvenile Large White Polish pigs with clinically diagnosed Lawsonia intracellularis infection (PPE; n=3) and a group of uninfected controls (C; n=3) were studied. Ileal tissue from each animal was processed for dual-labelling immunofluorescence using antiserum specific for protein gene product 9.5 (PGP 9.5) in combination with antiserum to one of: vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), somatostatin (SOM), neuropeptide Y (NPY) or galanin (GAL). In infected pigs, enteric neurons were found in ganglia located within three intramural plexuses: inner submucosal (ISP), outer submucosal (OSP) and myenteric (MP). Immunofluorescence labelling revealed increases in the number of neurons containing GAL, SOM, VIP and CGRP in pigs with PPE. Neuropeptides may therefore have an important role in the function of porcine enteric local nerve circuits under pathological conditions, when the nervous system is stressed, challenged or afflicted by disease such as PPE. However, further studies are required to determine the exact physiological relevance of the observed adaptive changes.

Immunologic status in pediatric cardiosurgical patients with chylothorax.

OBJECTIVE: The impact of lymphocyte and immunoglobulin loss on immunologic status has not been extensively studied in children with chylothorax. The purpose of this study was to evaluate immunologic profile of pediatric cardiosurgical patients who developed infection while suffering from prolonged postoperative chylothorax. METHODS: We retrospectively reviewed immunologic findings in 16 pediatric cardiac patients with post-operative chylothorax persisting ?7 days. Patients were on total parenteral nutrition, received colloides for replacement of chylous losses, and antibiotics and/or antimycotics for treatment of infection. Immunologic evaluation included immunoglobulin levels, cellular immunity, and phagocytic activity. For every parameter z-score was calculated according to age-dependent nomograms and t-test was used to compare z-score distribution with normal distribution. RESULTS: The immunoglobulin (IgG, IgM, and IgA) levels did not significantly differ from normal values, although 25% patients had IgG levels below normal range. The relative and absolute counts of peripheral blood lymphocytes were lower (p < 0.001) than normal values. Absolute numbers of blood B-lymphocytes (CD19+), T-lymphocytes (CD3+), helper/inducer T-cells (CD4+), and suppressor/cytotoxic T-cells (CD8+) were also below normal range (p < 0.001); however, their relative percentages and a CD4+/CD8+ ratio were within normal limits. The percentage and absolute number of natural killer cells (CD16+), phagocytic and metabolic activity of polymorphonuclear leukocytes did not differ from normal values. CONCLUSIONS: Persisting chylothorax results in B-cell and T-cell lymphopenia with proportional decline of CD4+ and CD8+ cells. Hypogammaglobulinemia observed in other studies has not been detected in this series probably due to administered plasma. Effects of these immunologic alterations on development of infection are unknown (Tab. 2, Ref. 13).

Arrhythmias in congenital heart defects.

AIM OF THE STUDY: Evaluation of the incidence and severity of late arrhythmias in patients with predisposing congenital heart defects--either due to the anatomy of the defect itself or as a result of a particular type of surgical intervention. PATIENTS AND METHODS: In a retrospective long-term study authors analyzed 158 patients (divided into 5 groups) with congenital heart defects after surgical correction. Evaluated were: the incidence of rhythm disturbances, the type of arrhythmia and the need for medication or intervention. RESULTS: The most rhythm disturbances occurred in patients after physiological correction of D-transposition of the great arteries (68.5%) and these patients also mostly needed medication or pacemaker implantation; followed were by patients with hypoplastic left heart syndrome after Fontan procedure (40%), then were patients after long-term correction of tetralogy of Fallot (31.1%), atrial septal defect sinus venosus type with partial anomalous pulmonary venous return after Warden correction (25.7%) and congenitally corrected L-transposition of the great arteries (25 %). Most of these arrhythmias were asymptomatic and there was no need to treat them. There was an increased incidence of arrhythmias with time (p < 0.05). DISCUSSION: During childhood in patients after surgical correction late arrhythmias mostly do not represent a severe problem, but with time, when reaching adulthood, this may be an issue. It is therefore very important to understand the anatomy, physiology and the arrhythmogenic substrate of every high risk congenital heart defect (Tab. 2, Fig. 6, Ref. 10).

The distribution and chemical coding of intramural neurons supplying the porcine stomach - the study on normal pigs and on animals suffering from swine dysentery.

The present study was designed to investigate the expression of biologically active substances by intramural neurons supplying the stomach in normal (control) pigs and in pigs suffering from dysentery. Eight juvenile female pigs were used. Both dysenteric (n = 4; inoculated with Brachyspira hyodysenteriae) and control (n = 4) animals were deeply anaesthetized, transcardially perfused with buffered paraformalehyde, and tissue samples comprising all layers of the wall of the ventricular fundus were collected. The cryostat sections were processed for double-labelling immunofluorescence to study the distribution of the intramural nerve structures (visualized with antibodies against protein gene-product 9.5) and their chemical coding using antibodies against vesicular acetylcholine (ACh) transporter (VAChT), nitric oxide synthase (NOS), galanin (GAL), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), Leu(5)-enkephalin (LENK), substance P (SP) and calcitonin gene-related peptide (CGRP). In both inner and outer submucosal plexuses of the control pigs, the majority of neurons were SP (55% and 58%, respectively)- or VAChT (54%)-positive. Many neurons stained also for CGRP (43 and 45%) or GAL (20% and 18%) and solitary perikarya were NOS-, SOM- or VIP-positive. The myenteric plexus neurons stained for NOS (20%), VAChT (15%), GAL (10%), VIP (7%), SP (6%) or CGRP (solitary neurons), but they were SOM-negative. No intramural neurons immunoreactive to LENK were found. The most remarkable difference in the chemical coding of enteric neurons between the control and dysenteric pigs was a very increased number of GAL- and VAChT-positive nerve cells (up to 61% and 85%, respectively) in submucosal plexuses of the infected animals. The present results suggest that GAL and ACh have a specific role in local neural circuits of the inflamed porcine stomach in the course of swine dysentery.

Re-examination of the topographical localization of facial nucleus in the pig.

Previous publications have provided different descriptions of the topographical organization of the facial nucleus of the pig. Since swine is used in biomedical research due to its embryological, anatomical and physiological similarities to human, we have reinvestigated the anatomical organization of the facial nucleus with application of fluorescent retrograde tracer Fast Blue, antibody to choline acetyltransferase and acetylcholinesterase histochemistry. Our findings demonstrate that in the porcine medulla facial motoneurons constitute a large cellular group occupying the ventro-lateral medulla. The neuronal group is interposed rostro-caudally between the superior and inferior olive, and located ventro-medially to the spinal nucleus of the trigeminal nerve. The present results clarify the anatomical description of this important brain stem nucleus in the pig.

The influence of experimental ileitis on the neuropeptide coding of enteric neurons in the pig.

In the present study, both the ELISA test and immunohistochemical staining were used to investigate the influence of artificially induced ileitis on the chemical coding of enteric neurons in the pig. The ileum wall in experimental (E) pigs was injected in multiple sites with 4% paraformaldehyde to induce inflammation, while in the control (C) animals, the organ was injected with 0.1M phosphate buffer (pH 7.4). Three days after ileitis induction, samples of ileum wall from all the animals were evaluated for VIP, SP, CGRP, NPY, GAL and SOM concentration (ELISA test) and the expression of these biologically active substances by the enteric neurons (immunohistochemical staining). Quantitative results showed that ileitis decreased tissue concentration of VIP, CGRP and SOM but increased tissue concentration of SP, NPY and GAL. Immunochemistry revealed that in both the experimental and control pigs, VIP-positive (VIP+) nerve fibers supplied mainly ileal blood vessels, and the labeled pericarya were located in the inner (ISP) and outer submucous plexus (OSP). SP+ and CGRP+ nerve terminals were found in both the mucous and muscular membrane, while the labeled pericarya were found in ISP, OSP and myenteric plexus (MP). In both C and E pigs, the very few nerve terminals containing NPY and SOM were located mainly in the mucous membrane. NPY- or/and SOM-immunopositive nerve cell bodies were found in ISP, OSP and MP. GAL+ nerve fibers supplied all layers of the ileum and were most numerous in the muscular membrane, while the labeled pericarya were present in all the enteric plexuses. The present results suggest that enteric neurons are highly plastic in their response to inflammation.

Immunohistochemical characterization of neurons in the porcine ciliary ganglion.

The present study was aimed at disclosing the chemical coding of nerve structures in the porcine ciliary ganglion (CG) using immunohistochemical methods. The substances under investigation included markers of "classical" neurotransmitters, choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DbetaH) as well as neuropeptides, somatostatin (SOM), galanin (GAL), substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY). Immunoreactivity to ChAT and VAChT was found virtually in all the neuronal somata and in numerous intraganglionic, varicose nerve fibres which often formed basket-like formations around the nerve cell bodies. Many CG neurons contained immunoreactivity for SOM (46%) or GAL (29%). Interestingly, a small number (approx. 1%) of the cholinergic somata stained for TH but not for DbetaH; nevertheless, some extra- and intraganglionic nerve fibres displayed immunoreactivity for DbetaH or TH. The CG perikarya stained neither for vasoactive intestinal polypeptide (VIP) nor for neuropeptide Y (NPY), but some NPY- or VIP-positive nerve terminals were observed within nerve bundles distributed outside the ganglion. SP- and CGRP-immunoreactivity was found in some intraganglionic nerve fibres only. The present study revealed that the porcine CG consists of cholinergic neurons many of which contain SOM and GAL. Thus, it can be assumed that in the pig, these neuropeptides are involved, complementary to acetylocholine, in the parasympathetic postganglionic nerve pathway to structures of the eye including the ciliary and iris sphincter muscles.

The distribution and chemical coding of neurons in the celiac-superior mesenteric ganglion complex supplying the normal and inflamed ileum in the pig.

The present study investigated the chemical coding of neurons in the celiac-superior mesenteric ganglion complex supplying the normal (n=4) and inflamed (n=4) ileum (chemically-induced inflammation) in juvenile pigs using retrograde tracing combined with immunohistochemistry. Ileum-projecting neurons (IPN) were predominantly distributed in the left and right superior mesenteric pools of the ganglion. The majority of them were adrenergic (tyrosine hydroxylase-positive) and also contained neuropeptide Y, somatostatin or galanin. No clear-cut differences in the distribution and chemical coding of IPN were found between normal and inflamed pigs. However, in the inflamed group, the density of peptidergic, IPN-associated nerve fibres was higher than that found in the control group.

Distribution of neurons containing leptin receptors in the hypothalamus of the pig.

Leptin, secreted by white adipocytes, has profound feeding, metabolic, and neuroendocrine effects. Leptin acts on the brain, but specific anatomical sites and pathways responsible for mediating these effects are still unclear. We have systematically examined the distribution of leptin receptor containing neurons in the porcine hypothalamus by means of immunohistochemical staining methods. Leptin receptor immunoreactivity (OBR-IR) was observed in both the preoptic area and anterior hypothalamic area. No immunoreactive structures were found in the median eminence. Only single, small neurons were observed in the arcuate nucleus. The most abundant OBR-IR cell bodies were located in the supraoptic nucleus. In the paraventricular nucleus, OBR-IR neurons were moderate in number. Single, dispersed neurons were found in the ventromedial nucleus. These findings indicate that there are distinct OBR-IR neuronal populations in the porcine hypothalamus and leptin not only plays an integrative role in feeding behavior, but also in neuroendocrine activity.

Leptin receptors, NPY, and tyrosine hydroxylase in autonomic neurons supplying fat depots in a pig.

The goal of this study was to determine the immunohistochemical characteristics of peripheral adrenergic OBR-immunoreactive (OBR-IR) neurons innervating adipose tissue in a pig. The retrograde tracer, Fast Blue (FB), was injected into either the subcutaneous, perirenal, or mesentery fat tissue depots of three male and three female pigs each with approximately 50 kg body weight. Sections containing FB(+) neurons were stained for OBR, tyrosine hydroxylase (TH) or neuropeptide Y (NPY) using a double labeling immunofluorescence method. OBR, TH, and NPY immunoreactivities were present in the thoracic (T) and lumbar (L) ganglia of the sympathetic chain, as well as in the coeliac superior mesenteric ganglion (CSMG), inferior mesenteric ganglion (IMG), intermesenteric ganglia (adrenal-ADG, aorticorenal-ARG, and ovarian-OG or testicular-TG ganglion). These results indicate that, in addition to neuroendocrine functions, leptin may affect peripheral tissues by acting on receptors located in sympathetic ganglion neurons.

Immunohistochemical study of the otic ganglion in the pig.

The presence of choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), galanin (GAL), substance P (SP) and calcitonin gene-related peptide (CGRP) was studied in neurons and nerve fibers of the porcine otic ganglion. ChAT-positive neurons were very numerous while VAChT-positive nerve cells were moderate in number. The number of neurons containing NPY and VIP was lower and those containing SOM, GAL, SP or CGRP were observed as scarce, or single nerve cells. The above mentioned substances (except SOM) were present in nerve fibers of the ganglion. ChAT- and VAChT-positive nerve fibers were numerous, while the number of nerve terminals containing NPY, VIP and SP was lower. GAL- and CGRP-positive nerve fibers were scarce.

Influence of active immunization against GnRH on VIP- and NPY-positive innervation of the porcine testis.

The influence of an anti-GnRH vaccine on VIP- and NPY-positive innervation of testes was studied in the pig. The immunization prevented the occurrence of changes in the pattern of VIP- and NPY-positive testicular innervation associated with the sexual maturation: it maintained the density of innervation at the high level characteristic for sexually immature animals. The effect was dependent on the method of immunization: the application of two doses of the vaccine was more efficient than application of only one dose, and vaccination with adjuvant was more efficient than vaccination with the plain vaccine. The studies on VIP and NPY concentration in the testicular tissue with radioimmunoassay (RIA) revealed immunization-dependent changes in the peptide concentration, however, some discrepancies between morphological changes and peptide levels were observed.

Distribution and immunohistochemical characterisation of paracervical neurons innervating the oviduct in the pig.

The present study was aimed at disclosing the distribution of paracervical neurons projecting to the ampulla and isthmus of the porcine oviduct and the pattern(s) of co-existence of tyrosine hydroxylase (TH), dopamine beta-hydroxylase (D beta H), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP) and nitric oxide synthase (NOS) within these nerve cell bodies. The fluorescent retrograde tracer Fast Blue (FB) was injected into the wall of the ampullar (n = 3) and isthmal (n = 3) part of the organ in six sexually immature female pigs. After a survival period of three weeks paracervical ganglia (PCG) were collected. 10 microns-thick cryostat sections of the ganglia were examined for the presence of FB-positive (FB+) nerve cells under the fluorescent microscope. Tracered neurons were counted in every third section and processed for double-labelling immunofluorescence according to the method of Wessendorf and Elde. 78.6% of FB+ neurons were projecting to the isthmus while 21.4% of the studied population innervated the ampulla of the oviduct. Double-labelling immunofluorescence revealed the existence of the following different chemically coded subpopulations of the studied perikarya: TH+/D beta H+, TH+/NPY+, TH+/NOS+, TH+/NOS-, SP-/NOS+, SP+/CGRP+.

[High-frequency pressure ventilation with high positive end-expiratory pressure in the treatment of respiratory failure in neonates]. / Vysokofrekvencná tlakovo riadená ventilácia s vysokým pozitívnym koncovoexspiracným tlakom v liecbe respiracného zlyhania novorodencov.

The authors present results of group of 13 neonates treated with high frequency positive pressure ventilation (HFPPV) with high positive end-expiratory pressure (PEEP) for severe respiratory failure. The ventilatory protocol was based on the following principles: a) higher mean airway pressure (MAP) to achieve adequate oxygenation, b) MAP titrated mainly with PEEP, c) fraction of inspired oxygen (FiO2) below 0.6, d) small tidal volumes 3-6 ml/kg, e) ventilatory rates to achieve normocapnia in newborns with persistent pulmonary hypertension and to allow permissive hypercapnia in others. During HFPPV, the maximum values for respiratory rate, PEEP, MAP and peak inspiratory pressures (PIP), the incidence of airleak and the need for inotropic support were recorded. The values for arterial partial pressure of oxygen (paO2), FiO2, paO2/FiO2 and MAP during conventional ventilation and 30 minutes after initiation of HFPPV were statistically analyzed. paO2 increased from 8.0 kPa (3.3-10.4) to 11.8 kPa (7.3-16.2, p < 0.001) and paO2 (torr)/FiO2 increased from 62.2 (24.7-101.2) to 157.5 (62.2-275.2, p < 0.001) 30 minutes after institution of HFPPV when MAP was increased from 11.8 cmH2O (9-13.8,) to 17.2 H2O (14.8-22.2) p < 0.001. This allowed turning down FiO2 from 1 (0.6-1) to 0.6 (0.4-1 p < 0.001). Maximal ventilatory rates used were in average 60/min (50-105), PEEP 8 cmH2O (6-10), PIP 30 cmH2O (26-45), MAP 18.8 cmH2O (14.8-22.2). Air leak did not occur in any patient. Catecholamines were used in 8 patients. The duration of ventilatory support lasted in average 6 days (2-18). All patients were successfully extubated. 5 of them required nasal continuous positive airway pressure (14 hours--7 days). (Tab. 3, Fig. 3, Ref. 19.)

Differences in the distribution and chemical coding between neurons in the inferior mesenteric ganglion supplying the colon and rectum in the pig.

The distribution and chemical coding of neurons in the porcine left and right inferior mesenteric ganglion projecting to the ascending colon and rectum have been investigated by using combined retrograde tracing and double-labelling immunohistochemistry. The ganglion contained many neurons supplying both gut regions. The colon-projecting neurons (CPN) occurred exclusively in the cranial part of the ganglia where they formed a large cluster distributed along the dorso-lateral ganglionic border and a smaller cluster located close to the caudal colonic nerve output. The rectum-projecting neurons (RPN) formed a long stripe along the entire length of the lateral ganglionic border and, within the right ganglion only, a small cluster located close to the caudal colonic nerve output. Immunohistochemistry revealed that the vast majority of the CPN and RPN were noradrenergic (tyrosine-hydroxylase-positive). Many noradrenergic neurons supplying the colon contained somatostatin or, less frequently, neuropeptide Y. In contrast, a significant subpopulation of the noradrenergic RPN expressed neuropeptide Y, whereas only a small proportion contained somatostatin. A small number of the non-adrenergic RPN were cholinergic (choline-acetyltransferase-positive) and a much larger subpopulation of the nerve cells supplying both the colon and rectum were non-adrenergic and non-cholinergic. Many cholinergic neurons contained neuropeptide Y. The non-adrenergic non-cholinergic neurons expressed mostly somatostatin or neuropeptide Y and some of those projecting to the rectum contained nitric oxide synthase, galanin or vasoactive intestinal polypeptide. Many of both the CPN and RPN were supplied with varicose nerve fibres exhibiting immunoreactivity against Leu5-enkephalin, somatostatin, choline-acetyltransferase, vasoactive intestinal polypeptide or nitric oxide synthase The somatotopic and neurochemical organization of this relatively large population of differently coded inferior mesenteric ganglion neurons projecting to the large bowel indicates that these cells are probably involved in intestino-intestinal reflexes controlling peristaltic and secretory activities.

Distribution of efferent neurones innervating the oviduct in the pig.

This study was aimed, by means of the retrograde tracing technique, at disclosing the distribution of efferent neurones innervating the porcine oviduct. The fluorescent retrograde tracer Fast Blue was injected into the wall of the right oviduct in six juvenile pigs during laparotomy performed under anaesthesia. After a recovery period of 3 weeks the animals were reanaesthetised, perfused with 4% buffered paraformaldehyde (pH 7.4) and different ganglia, thought to be potent sources of the efferent innervation, were collected. The occurrence and distribution of Fast Blue-positive neurones were studied in the sympathetic chain and prevertebral ganglia, including the coeliac-superior mesenteric ganglion complex, adrenal ganglion, aorticorenal ganglion, ovarian ganglion and inferior mesenteric ganglion. The labelled neurones were found only in the right, ipsilateral ganglia. The largest number of Fast Blue-positive neurones was found in the inferior mesenteric ganglion, ovarian ganglion and in the coeliac-superior mesenteric ganglion complex. In the inferior mesenteric ganglion, the Fast Blue-positive neurones showed a tendency to gather in the dorso-cranial and the dorso-caudal region of the ganglion, forming two discrete "oviductal centres". The aortico-renal and adrenal ganglion contained a smaller population of Fast Blue-positive nerve cell bodies. The smallest number of Fast Blue-positive neurones was found in the sympathetic chain ganglia (T14-L5). The localisation of Fast Blue-positive neurones in the sympathetic chain ganglia and prevertebral ganglia suggests that these nerve structures play a fundamental role in the efferent innervation of the porcine oviduct.

Has active immunization against gonadotrophin-releasing hormone any effect on testis innervation in the pig? An immunohistochemical study.

The innervation of porcine testes was studied in intact animals and in boars undergoing active immunization against gonadotrophin-releasing hormone (GnRH) by means of immunohistochemistry using antibodies to tyrosine hydroxylase (TH), dopamine beta-hydroxylase (D beta H), vasoactive intestinal polypolypeptide (VIP), neuropeptide Y (NPY), synaptosome-associated protein of 25 kDa (SNAP-25) and protein gene product 9.5 (PGP 9.5). Moreover, the distribution of luteinizing hormone (LH) receptors in clusters of Leydig cells was also investigated. To identify these cells easily, either the NADPH-diaphorase histochemical technique or the Mayer counter-staining procedure was applied. Differences in the distribution pattern and relative density of particular subsets of intratesticular nerve fibres were observed in immunized boars as compared to those found in the intact animals. In the testes of non-treated animals, only single TH-immunoreactive (TH-IR) nerve fibres were observed. However, many D beta H-IR nerve terminals surrounded blood vessels in the tunica albuginea and parenchyma. Very scarce VIP-IR nerves occurred only in the tunica albuginea, mainly in close vicinity to blood vessels. Immunoreactivity to NPY occurred in single nerve fibres. Immunoreactivity to SNAP-25 and PGP 9.5 was found in single nerve fibres distributed mainly in the tunica albuginea. The interstitial cells were heavily stained for LH-receptors and NADPH-diaphorase. In the testes of immunized animals, only single TH-IR nerve fibres, scattered mainly in the tunica albuginea, were observed. Some TH-IR nerve terminals were also encountered in the parenchyma of the organ, where they were always associated with blood vessels. D beta H-IR nerve fibres formed a dense network distributed throughout the testis in association with the capsule, vasculature and interstitium. Some fibres were observed to run between seminiferous tubules. VIP-IR nerve fibres were located in the neighbourhood of blood vessels in the tunica albuginea and parenchyma. Only single VIP-IR nerves were found between seminiferous tubules. Numerous NPY-IR nerve fibres occurred in the tunica albuginea and parenchyma of the organ. SNAP-25-IR and PGP 9.5-IR nerve terminals formed a dense network distributed throughout the testis and many fibres were observed between seminiferous tubules. Interstitial cells were very weakly stained for LH receptors or NADPH-diaphorase.