Use of glyoxylic acid in the demonstration of autonomic nerve profiles

Inflammation and Neurotransmission of the Vescico-Uterine Space in Cesarean Sections

Collagen IV and laminin play a key role in regulating stiffness, elasticity and flexibility of the vescico-uterine space (VUS) tissue. The neurotensin (NT), the neuropeptide tyrosine (NPY) and the protein gene product 9.5 (PGP 9.5) possessing vasorelaxation and tissue vascularization activities, play key roles in cervical ripening, scar innervations and pain control. We propose that the integrity of these substances in VUS tissue is compromised after Cesarean section (CS), since wound healing disturbances and pelvic pain, as well as pregnancy and delivery complications, are related with lower uterine segment dysfunctions after CS. Therefore, the contents of collagen IV, laminin, NT, NPY and PGP 9.5 nerve fibres from the VUS tissue samples obtained during the first CS and the repeated CS were comparatively studied. VUS specimens were collected from 104 patients during CS and evaluated by immunohistochemistry. Collagen IV and laminin were mostly found in the vascular membrane bounds and their images were quantitatively evaluated by Quantimet Leica analyzer software. Differences of collagen IV, laminin, NT, NPY and PGP 9.5 values in VUS tissue between the first CS and the repeat CS samples were calculated by Student's Mest. Reduced laminin and increased collagen IV values were observed in the VUS scar tissue after the repeated CS in comparison with those of VUS intact tissue obtained during the first CS. Significantly higher values of nerve fibres, containing NT, NPY and PGP 9.5 were registered in intact VUS tissue samples, respectively 5±0.7, 7±0.6 and 5±0.9 CU, than those of VUS scar tissue samples obtained during the repeated CS, respectively 3±0.6,2±0.4 and 3±0.7 CU (p<0.05). The authors observed increased collagen IV and reduced laminin values after the repeated CS which might be the key signs of inflammatory damage of VUS scar tissue by CS. These findings were strengthened by the registration of decreased NT, NPY and PGP 9.5 values in the same samples, which are important neurotransmitters and are responsible for optimal wound healing, pain control and lower uterine segment functions.

Neonatal androgenization affects the efficiency of β-adrenoceptor-mediated modulation of thymopoiesis

We tested the hypothesis that neonatal androgenization affects the efficacy of β-adrenoceptor (β-AR)-mediated fine tuning of thymopoiesis in adult female rats by modulating the thymic noradrenaline (NA) level and/or β-AR expression. In adult rats administered with 1000 μg testosterone enanthate at postnatal day 2 a higher density of catecholamine (CA)-synthesizing thymic cells, including thymocytes, and a rise in their CA content was found. In addition, in these animals increased thymic noradrenergic nerve fiber fluorescence intensity, reflecting their increased CA content, was detected. These changes were followed by an increase in thymic NA concentration. The rise in thymic NA content in thymic nerve fibers and cells was associated with changes in the expression of mRNA for enzymes controlling pivotal steps in NA biosynthesis (tyrosine hydroxylase, dopamine-β-hydroxylase) and inactivation (monoamine oxidase). In contrast, the thymic level of β(2)-AR mRNA on a per cell basis and the receptor surface density on thymocytes was reduced in testosterone-treated (TT) rats. As a consequence, 14-day-long treatment with propranolol, a β-AR blocker, was ineffective in modulating T-cell differentiation/maturation in TT rats. In conclusion, the study indicates the importance of the neonatal sex steroid milieu for shaping the immunomodulatory capacity of the thymic NA/β-AR signaling system in adult rats.

Intrinsic innervation and dopaminergic markers after experimental denervation in rat thymus

The aim of this study was to examine rat thymus innervation using denervation techniques and to explore the related microanatomical localization of dopamine, D1, D2 receptors and dopamine membrane transporter (DAT).

In the thymus subcapsular region, the parenchymal cholinergic fibers belong exclusively to phrenic nerve branching. No somatic phrenic nerve branching was detected in any other analysed thymus lobule regions.

In rats subjected to sympathetic or parasympathetic ablation, it was observed that catecholaminergic and cholinergic nerve fibers respectively contributed to forming plexuses along vessel walls.

In the subcapsular and septal region, no parenchymal nerve branching, belonging to sympathetic or parasympathetic nervous system was noted. Instead, in the deep cortical region, cortico-medullary junction (CM-j) and medulla, catecholaminergic and cholinergic nerve fibers were detected along the vessels and parenchyma.

Dopamine and dopamine receptors were widely diffused in the lobular cortico-medullary junction region and in the medulla, where the final steps of thymocyte maturation and their trafficking take place.

No variation in dopamine and DAT immune reaction was observed following total or partial parasympathectomy or phrenic nerve cutting. After chemical or surgical sympathectomy however, neither dopamine nor DAT immune reaction was noted again. Instead, D1 and D2 dopamine receptor expression was not affected by thymus denervation.

In rats subjected to specific denervation, it was observed the direct intraparenchymal branching of the phrenic nerve and sympathetic and parasympathetic fibers into thymus parenchyma along vessels. These findings on the dopaminergic system highlight the importance of neurotransmitter receptor expression in the homeostasis of neuroimmune modulation.

Sexual dimorphism in the catecholamine-containing thymus microenvironment: a role for gonadal hormones

The study was undertaken to explore whether there were: i) apart from neural and circulatory, some other sources of catecholamines (CAs) in rat thymus and ii) gender-specific differences in thymic CA levels, and if so to elucidate the role of sex steroids in this phenomenon. Tyrosine hydroxylase (TH) immunoreactivity was found in thymocytes and thymic epithelial cells (some of which showed morphological features of nurse cells). The density of CA-synthesizing cells was greater in male than in female rats. Noradrenaline (NA), but not dopamine (DA), was detected in thymocytes. NA and DA levels in thymi, and the NA level in thymocytes, were higher in male rats. To explore the putative role of sex steroids in this dichotomy in the thymi of adult rats gonadectomized (Gx) or sham-Gx at the age of 30 days the density of TH+ cells and CA levels were measured. Gonadectomy abolished sexual dimorphism in the density of thymic TH+ cells (diminishing their density in male rats) and thymic CA levels (the NA levels were reduced in rats of both sexes and also the DA level in male rats). Therefore, it can be assumed that testicular and ovarian hormones control thymic NA and DA levels via different mechanisms. Moreover, in Gx rats, despite the decrease in the overall thymic NA level, an increase in the thymocyte NA level was found indicating that gonadal hormones exert differential effects on the NA level in distinct thymic cellular compartments.

Clinical and morphological characteristics of head-facial haemangiomas

Background

Haemangiomas of the head or face are a frequent vascular pathology, consisting in an embryonic dysplasia that involves the cranial-facial vascular network. Haemangiomas show clinical, morphological, developmental and structural changes during their course.

Methods

The clinical characteristics of head-facial haemagiomas were studied in 28 individuals (9 males and 19 females) admitted in our Hospital. Sixteen of these patients(n = 16) underwent surgery for the removal of the haemangiomas. All the removed tissues were transferred in experimental laboratories for the staining of microanatomical details, somatic and visceral nerve fibres, adrenergic and catecholaminergic nerve fibres. Beta-adrenergic receptors were died with a fluorescent method. All results were submitted to the quantitative analysis of images and statistical evaluation of the data.

Results

The morphological results revealed numerous micro-anatomical characteristics of the haemangiomatous vessels. The somatic and visceral nerve fibres were poor and located exclusively in the adventitial layer. There was a marked decrease of adrenergic nerve fibres in the haemangiomatous vessels. The fluorescence of catecholaminergic nerve fibres and the overall area of fluorescent structures were also decreased in haemangiomatous vessels. Beta adrenergic receptors are strongly decreased in haemangiomatous vessels. The morphometrical analysis of images and statistical evaluation of the data confirmed all our experimental results.

Conclusion

The catecholaminergic innervation of the human haemangiomatous vessels comprises nerve fibres containing the main catecholaminergic neurotransmitters that are sympathetic in nature. These neurotransmitters are closely related to beta-adrenergic receptors.

The sympathetic nervous system plays a key role in the control of the vascular bed flow and vascular motility in both normal and haemangiomatous vessels.

Re-evaluation and quantification of the different sources of nerve fibres supplying the rat eye

The denervation and/or the removal of peripheral nerve ganglia are useful surgical techniques for studying the source and distribution of peripheral nerves in all organs, including the eye. The amount and distribution of the remaining nerve fibres supplying the eye (after sectioning of various types of nervous fibres and/or removal of nerve ganglia) were evaluated in the rat. Male Sprague-Dawley rats were anaesthetized and one or more of the following nervous tissues were removed: superior cervical ganglion, main ciliary ganglion, pterygopalatine ganglion, trigeminal ganglion and the ophthalmic-maxillary nerve. In some animals, chemical sympathectomy was performed by administration of 6-OH dopamine. The eyes were cut in serial sections, but only three regions (cornea, iris and choroid) were harvested and submitted for various nerve fibre staining techniques. The results were quantified and statistically analysed. Superior cervical ganglionectomy and/or chemical sympathectomy induced the destruction of almost all the catecholaminergic nerve fibres in the three examined regions of the rat eye. Removal of the ciliary ganglion (partial parasympathectomy) caused the destruction of about 60% of the cholinergic nerve fibres of the same regions of the rat eye, while subtotal parasympathectomy destroyed about 80% of the cholinergic nerve fibres. Surgical transsection of the ophthalmo-maxillary nerve or the removal of the trigeminal ganglion led to a degeneration of almost all sensitive nerve fibres of the three examined regions of the rat eye. The denervation experiments confirmed the presence of the different types of nerve fibres (sympathetic, parasympathetic and sensitive) in the three studied structures of the rat eye.

Distribution of Catecholaminergic Neurotransmitters and Related Receptors in Human Bronchus-Associated Lymphoid Tissue

BACKGROUND

The functions of the bronchus-associated lymphoid tissue (BALT) are under the control of the autonomic nervous system (sympathetic and parasympathetic nerve fibers).

OBJECTIVES

The relationships between the adrenergic nerve fibers and beta-adrenergic receptors were studied in the human BALT with the aim to demonstrate a probable neuromodulation.

METHODS

Morphological observations (staining with hematoxylin-eosin and scanning electron microscopy images) were carried out on samples of human BALT harvested during autopsies. Moreover, histochemical staining for norepinephrine (adrenaline = adrenergic nerve fibers) as well as for other catecholamines was performed. Finally, beta-adrenergic receptors were stained by means of a beta-blocking, radiolabeled drug (pindolol 125I). All our data were submitted to morphometric analysis (quantitative analysis of images and statistical analysis of data).

RESULTS

Our results provide direct evidence of the presence and distribution of catecholaminergic nerve fibers and related beta-adrenergic receptors in BALT. beta-Adrenergic receptors are present above all in the most richly innervated part of the BALT, and are, therefore, in close relationship with their related adrenergic nerve fibers.

CONCLUSIONS

Studies on the distribution of adrenergic neurotransmitters and related beta-adrenergic receptors in the human BALT are the first step for the demonstration of a probable neuromodulation of BALT.

Catecholaminergic nerve fibers in bronchus-associated lymphoid tissue: age-related changes

Age-related changes of the catecholaminergic nerve fibers of the trachea, bronchial smooth muscle, lung capillaries and bronchus-associated lymphoid tissue (BALT) were studied in male Wistar rats aged 3 months (young), 12 months (adult) and 24 months (old/aged). Catecholamine histo- and immuno-fluorescence techniques were used, associated with image analysis and high pressure liquid chromatography with electrochemical detection of nor-epinephrine (nor-adrenaline). In young rats, blue-green fluorescent nerve fibers supply the trachea-bronchial smooth muscle and tracheal and bronchial glands. These structures are innervated by a delicate network of nerve fibers, being rich in varicosities. Pulmonary capillaries are sparsely innervated. The highest nor-epinephrine concentration was found in the trachea and bronchi, followed by BALT. The density and the pattern of noradrenergic nerve fibers of the trachea-bronchial tree or of the pulmonary vessels were similar in young and adult rats. In aged rats, a loss of noradrenergic nerve fibers, involving primarily the supply to the smooth muscle of the trachea-bronchial tree, was observed. Fluorescence microscopic techniques demonstrated a higher sensitivity than nor-epinephrine assay in detecting changes of the sympathetic nerve supply of the trachea-bronchial tree, pulmonary vessels and BALT. The possible significance of reduced noradrenergic nerve supply of the trachea-bronchial-pulmonary tree in aged rats is discussed.

Occurrence of catecholaminergic nerve fibers in the human uveoscleral tissue in conditions of normal and raised intraocular pressure

The distribution of catecholaminergic nerve fibers (CNF) in human uveoscleral tissue was studied in six human eyes with normal intraocular pressure and in five eyes with increased pressure. The eyes with increased pressure had no visual field alterations and the patients did not have any glaucoma-related optic neuropathies. The amount of norepinephrine in these structures was also analysed. Catecholaminergic nerve fibers were detected by means of fluorescence microscopy and were counted using the quantitative analysis of images. Our results demonstrate that the occurrence of catecholaminergic nerve fibers (expressed in Conventional Units = C.U.) in human uveoscleral tissue is 15.4 +/- 1.6 C.U. in eyes with normal intraocular pressure. In eyes with increased intraocular pressure, these values were 12.2 +/- 1.2 C.U. Moreover, the amount of norepinephrine in tissue homogenates of the same eyes was evaluated and found to be 21.7 +/- 1.3 microg/gr tissue fresh weight of the human uveoscleral tissue in eyes with normal intraocular pressure. This value decreased to 18.8 +/- 1.1 microg/gr tissue fresh weight in the same tissue in conditions of raised intraocular pressure. In these experiments, the small number of eyes examined made it difficult to draw general conclusions. However, the role of human uveoscleral tissue was emphasized by the rich catecholaminergic innervation. A decrease of catecholaminergic nerve fibers and norepinephrine occurs when intraocular pressure is elevated. The modifications of these parameters, involved in the sympathetic control of aqueous humor outflow, may support the hypothesis of a possible relevant role for the human uveoscleral tissue in different pathological conditions.

Effect of interferon on human thymus microenvironment

Interferon, a thymic immunostimulator, was used with the aim of assessing the importance of adrenergic nerve fibers (ANF) and/or AChE-positive nerve fibers (AChENF) in the regulation of some immunological functions in humans. Thymic normal control fragments and/or thymic fragments of immunostimulated patients were removed during surgical biopsies. Thymic slices were stained with eosin-orange (for the recognition of microanatomical details of the microenvironment) and with Bodian's method for staining of nerve fibers. Histofluorescence microscopy was employed for staining ANF. AChENFs were detected by means of the direct-coloring thiocholine method. All images were submitted to quantitative morphometrical analysis and statistical comparisons of data. Moreover, the amount of proteins and noradrenaline was measured on thymic homogenates of the same patients. Treatment with interferon induces substantial changes in the thymic microenvironment, on ANF, on AChENFs and on the total amount of proteins and noradrenaline in thymic tissue homogenates. In conclusion immunostimulation with interferon induces substantial changes in the whole thymus and in its microenvironment, involving both sympathetic and parasympathetic nerve fibers.

Adrenergic nerve fibres and mast cells: correlation in rat thymus

The interactions between adrenergic nerve fibres and mast cells (MCs) were studied in the thymus of adult and old rats by morphological methods and by quantitative analysis of images (QAIs). The whole thymus was drawn in adult (12 months old) rats: normal, sympathectomized or electrostimulated. Thymuses from the above-mentioned animals were weighed, measured and dissected. Thymic slices were stained with eosin orange for detection of microanatomical details and with Bodian's method for identification of the whole nerve fibres. Thymic MCs were stained with Astrablau. Histofluorescence microscopy was used for staining of adrenergic nerve fibres. Finally, all morphological results were submitted to the QAIs and statistical analysis of data. Our results suggest that after surgical sympathectomy, the greater part of adrenergic nerve fibres disappear while related MCs appear to show less evident fluorescence and few granules. On the contrary, electrostimulation of the cervical superior ganglion induced an increase in the fluorescence of adrenergic nerve fibres and of related MCs.

Age-related changes in dopamine D2 receptors in rat heart and coronary vessels

1. The distribution of dopamine D2 receptors in rat heart and coronary vessels and the possible age-related changes in D2 receptor density were studied. The pharmacological characteristics and the anatomical location of dopamine D2-like receptor sites in rat heart and coronary vessels were investigated using combined binding techniques and light microscopy autoradiography. 2. Samples of heart and coronary vessels were harvested from young and old rats. On frozen slices, dopaminergic D2 receptors were labelled by means of a selective D2 ligand, namely [3H]-spiroperidol (spiperone). Inhibition studies were performed using unlabelled agonists and/or labelled and unlabelled antagonists to define pharmacological specificity of the binding. Physiological experiments were performed to demonstrate the selective antagonism between D2 receptors and many dopaminergic drugs. 3. [3H]-Spiroperidol was bound to sections of rat heart and coronary artery (in a manner consistent with the labelling of dopamine D2-like receptors) with an equilibrium dissociation constant of approximately 2.4 +/- 0.7 nmol/L and a maximum capacity of binding sites of 65.8 +/- 4.5 fmol/mg protein. Experiments performed on sections of coronary veins did not allow the evaluation of specific binding. Autoradiography, observed with light microscopy, showed the development of specific silver grains within the whole wall of rat heart and coronary artery. The greater sensitivity to displacement by amisulpride, bromocriptine, domperidone, haloperidol, raclopride and L-sulpiride than to displacement by N-propyl-norapomorphine, quinpirole and clozapine suggests that the binding sites observed in these experiments are likely to belong to the dopamine D2 receptor subtype. 4. Comparing results in young and old rats, we observed numerous significant age-related changes, including a decrease in D2 receptors localized in rat heart and coronary artery wall. These D2 receptors show a specific location, in close relationship with dopaminergic nerve fibres. They decrease with age and their role remains unknown.

Occurrence of adrenergic nerve fibers in human thymus during immune response

The adrenergic nerve fibers (ANF), the neuropeptide Y-like immunoreactive nerve fibers (NPY-NF) and the noradrenaline (NA) amount were studied in the human thymus in subjects previously treated or not treated with interferon therapy with the aim to identify the changes due to the interferon therapy. This therapy has been used in patients affected by multiple sclerosis (MS). Biochemical and morphological methods were used associated with quantitative analysis of images. The whole thymuses were removed during autopsies in young and adult patients not treated with interferon. Moreover, samples of thymus were removed from patients, either young or adult who had previously been treated with interferon therapy, and subjected, for diagnostic reasons, to thymic biopsy. All samples of thymus were weighed, measured and dissected. Thymic slices were stained with Eosin-orange for detection of the microanatomical details, or with Bodian's reaction for recognition of nervous structures. Histofluorescence microscopy was used for detection of ANF, and immunofluorescence microscopy for recognition of NPY-like immunoreactive structures. All morphological results were subjected to quantitative analysis of images. Noradrenaline contained in thymic structures was measured by biochemical methods. Our results only concerned the effects of the therapy and suggested that treatment with interferon therapy induces many changes in the thymic structures: (1) The protein content of thymus is significantly increased; (2) the NA content in the thymus is also significantly increased; (3) NPY-like immunoreactive structures in the thymus are significantly increased; (4) occurrence of NPY-like immunoreactivity is particularly and significantly increased both in thymic microenvironment and in structures resembling nerve fibers; (5) ANF are significantly increased in the same thymic structures in which NPY-like immunoreactivity is also increased (i.e. thymic microenvironment and structures resembling nerve fibers). The morphological and biochemical changes observed can also explain the immunological changes induced in the thymus after immunostimulating therapy.

Interleukin 1beta as stimulator of the rat thymus

The effects of interleukin 1beta administration on the thymus of adult and old rats were studied in order to study the interactions between the nervous and immune systems and to confirm the important role played by catecholaminergic nerve fibres (CNF) in the regulation of thymic functions. Moreover, chemical sympathectomy was performed in a group of rats to study the effects on thymus of the destruction of the majority of CNF. Our results indicate that thymic stimulation (performed by means of interleukin 1beta) induces substantial changes in the fresh weight of the whole thymus, as well as in the thymic microenvironment, thymic nerve fibres, CNF, neuropeptide Y (NPY)-like positive nerve fibres and total amount of both proteins and norepinephrine in rat thymic tissue homogenates. The majority of CNF are destroyed after chemical sympathectomy with 6-OH-Dopamine (DA) and remain unchanged after treatment with interleukin 1beta.

Occurrence of adrenergic nerve fibers and of noradrenaline in thymus gland of juvenile and aged rats

Adrenergic nerve fibers (ANF) were studied in juvenile, adult and old rats by biochemical and morphological methods and by quantitative analysis of images (QAI). After chemical sympathectomy with neurotoxin 6-OH dopamine, the greater part of ANF disappeared. The whole thymus was drawn in juvenile normal or sympathectomized rats, in adult normal or sympathectomized rats and in old normal or sympathectomized rats. Thymuses from the above-mentioned animals were weighed, measured and dissected. Thymic slices were stained with eosin orange for the detection of the microanatomical details and with Bodian's method for the recognition of the whole nerve fibers. Histofluorescence microscopy was used for staining of ANF while immunofluorescence microscopy was employed for staining of neuropeptide Y (NPY)-like immunoreactivity. Biochemical dosage of proteins and of noradrenaline amount was performed. Finally, all morphological results were subjected to QAI. Our results suggest that: (1) total innervation of the thymus increases with age; (2) ANF do not change with age; (3) the content of noradrenaline in the thymus increases with age; and (4) NPY-like immunoreactive structures in the thymus decrease with age. Biochemical results are in accordance with the morphological ones and both are confirmed by means of QAI. The probable function of sympathetic innervation of rat thymus is also discussed.

Orchidectomy affects the innervation of the rat thymus

To assess a putative role of the neural pathways in transfer of information from the gonads to the thymus, adult AO rats were orchidectomized (ORX) or sham ORX (controls); sacrificed 1, 3, 7, or 15 days later and their thymi were analyzed for: (a) the concentrations of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) and distribution of monoamine-containing nerve profiles and (b) the acetylcholinesterase (AChE) activity and distribution of AChE-containing nerve profiles. Three days after the castration, an elevation in the level of both catecholamines, reflecting an increase in the overall intensity of nerve fibers autofluorescence, was found. Seven days post castration neither NA nor DA concentration differed from the appropriate control values, while 15 days after the surgery the concentration of NA was lower than that in the controls, most likely, due to diminished density of noradrenergic nerve profiles. In both the rats sacrificed 7 and 15 days after orchidectomy the concentration of 5-HT was reduced as result of a decrease in the density of 5-HT-containing autofluorescent cells. The activity of AChE was depressed one day after the surgery; then increased, so that 3 days post castration its value was higher than that in the sham ORX. After this increase, AChE activity decreased being, at postoperative day 7 and 15, lower than that in the controls. It seems that this decrease in AChE activity reflected, not only a reduction in the density of AChE-containing nerve fibers, but also a decrease in the density of AChE positive cells. Thus, the results indicate that orchidectomy can evoke changes in the T-cell maturation altering modulatory influences on this process coming via neural route, as well as those coming from the mast cells and AChE positive epithelial cells which constitute important component of the thymus microenvironment.

Intrinsic innervation of a reptilian esophagus (Podarcis hispanica)

We study the esophagus of Podarcis hispanica through different methods to clarify the structure and affinities of its wall innervation. The acetylcholinesterase method reveals cholinesterase activity in two submucosal nervous plexuses, with an increasing degree of structural complexity in the reptilian esophagus, compared with amphibians. Noradrenergic innervation, detected through fluorescence induced by formol, widely spreads its network in both the myenteric and submucosal plexuses (around the blood vessels in the external submucosal plexus, and to the glandular lamina propria in the inner submucosal plexus). Immunohistochemistry for vasoactive intestinal peptide shows a widespread innervation, with neurons clustered in ganglia and also scattered through the VIPergic network, only at the myenteric plexus. Immunohistochemistry for substance P shows a rich innervation along the entire wall of the esophagus, more concentrated in its caudal region, around the blood vessels. Electron microscopy shows the enteric neuronal ultrastructure and its relationship with the esophagus wall.

Relationships between monoaminergic and cholinergic innervation of the rat thymus during aging

The present study has been undertaken in order to investigate whether aging is accompanied by alterations in the thymic autonomic innervation. The results showed that in aged rats compared to young adult rats the density of monoaminergic histofluorescent nerve profiles decreased remarkably, while their pattern of intrathymic distribution remained unchanged. The thymic concentrations of noradrenaline (NA) and dopamine (DA) also significantly decreased between the age of 12 and 18 months. However, the density of thymic autofluorescent cells (afc) markedly increased over the same period, as well as the concentration of 5-hydroxytryptamine (5-HT). The aged rat thymus seemed to be able to maintain its cholinergic innervation in terms of density and pattern of distribution, while the density of cells with intracytoplasmic acetylcholinesterase (AChE) staining even increased. The neurochemical measurement showed an increase in the activity of AChE between the age of 9 to 18 months. The results indicate an altered relation between the components of thymic autonomic innervation of aged rats that might be related to the reduced immunocompetence of their T cells.