Submandibular gland secretory function in young adult and aged rats

An evaluation of submandibular gland secretory function was performed in young adult and aged male and female rats. No significant alterations in submandibular salivary flow rate or the concentrations of total protein, Na+,K+ and neutral sugar in the secreted saliva, were observed between different aged animals. Significant sex differences in salivary flow rate and total protein content were found.     

Age Related Changes from Youth to Adulthood in Rat Brain Cortex: Nitric Oxide Synthase and Mitochondrial Respiratory Function

Age related changes in brain cortex NO metabolism were investigated in mitochondria and cytosolic extracts from youth to adulthood. Decreases of 19%, 40% and 71% in NO production were observed in mitochondrial fractions from 3, 7, and 14 months old rats, respectively, as compared with 1-month-old rats. Decreased nNOS protein expression in 14 months old rats was also observed in mitochondria as compared with the nNOS protein expression in 1-month-old rats. Low levels of eNOS protein expression close to the detection limits and no iNOS protein expression were significantly detected in mitochondrial fraction for both groups of age. NO production in the cytosolic extracts also showed a marked decreasing tendency, showing higher levels than those observed in mitochondrial fractions for all groups of age. In the cytosolic extracts, however, the levels were stabilized in adult animals from 7 to 14 months. nNOS protein expression showed a similar age-pattern in cytosolic extracts for both groups of age, while the protein expression pattern for eNOS was higher expressed in adult rats (14 months) than in young animals. As well as in mitochondrial extracts iNOS protein expression was not significantly detected in cytosolic extracts at any age. RT-PCR assays indicated increased levels of nNOS mRNA in 1-month-old rats as compared with 14 months old rats, showing a similar pattern to that one observed for protein nNOS expression. A different aged pattern was observed for eNOS mRNA expression, being lower in 1-month-old rats as compared with 14 months old animals. iNOS mRNA was very low expressed in both groups of age, showing a residual iNOS mRNA that was not significantly detected. State 3 respiration rates were 78% and 85% higher when succinate and malate-glutamate were used as substrates, respectively, in 14 months rats as compared with 1-month-old rats. No changes were observed in state 4 respiration rates. These results could indicate 1 that nNOS and eNOS mRNA and protein expression can be age-dependent, and confirmed the nNOS origin for the mitochondrial NOS. During rat growth, the respiratory function seems to be modulated by NO produced by the different NOS enzymes: nNOS, eNOS and mtNOS present in the cytosol and in the mitochondria.     

Apoptotic responses to hindlimb suspension in gastrocnemius muscles from young adult and aged rats

Although apoptosis has been demonstrated in soleus during hindlimb suspension (HS), it is not known whether apoptosis is also involved in the loss of muscles dominated by mixed fibers. Therefore, we examined the apoptotic responses in gastrocnemius muscles of young adult and aged Fischer 344 x Brown Norway rats after 14 days of HS. The medial gastrocnemius muscle wet weight significantly decreased by 30 and 32%, and muscle wet weight normalized to the animal body weight decreased by 11 and 15% in young adult and aged animals, respectively, after HS. The extent of apoptotic DNA fragmentation increased by 119 and 61% in suspended muscles from young and aged rats, respectively. Bax mRNA increased by 73% in young muscles after HS. Bax and Bcl-2 protein levels were greater in suspended muscles relative to control muscles in both age groups. The level of cytosolic mitochondria-housed apoptotic factor cytochrome c was significantly increased in the mitochondria-free cytosol of suspended muscles from young and aged rats. In contrast, the release/accumulation of AIF, a caspase-independent apoptogenic factor, was exclusively expressed in the suspended muscles from aged rats. Our data also show that aging favors the proapoptotic signaling in skeletal muscle by altering the contents of Bax, Bcl-2, Apaf-1, AIF, caspases, XIAP, Smac/DIABLO, and cytochrome c. Furthermore, these results indicate that apoptosis occurs not only in slow-twitch soleus muscle but also in the mixed-fiber (predominately fast fibered) gastrocnemius muscle. Our data are consistent with the hypothesis that apoptotic signaling differs in young adult and aged gastrocnemius muscles during HS.     

Hindlimb unloading increases muscle content of cytosolic but not nuclear Id2 and p53 proteins in young adult and aged rats.

This study tested the hypothesis that inhibitor of differentiation-2 (Id2), p53, and heat shock proteins (HSP) are responsive to suspension-induced muscle atrophy. Fourteen days of hindlimb suspension were used to unload the hindlimbs and induce atrophy in gastrocnemius muscles of young adult and aged rats. Following suspension, medial gastrocnemius muscle wet weight was reduced by approximately 30%, and the muscle wet weight normalized to the animal body weight decreased by 11 and 15% in young adult and aged animals, respectively. mRNA abundances of Id2, p53, HSP70-2, and HSP27 did not change with suspension, whereas HSP70-1 mRNA content was lower in the suspended muscle compared with the control muscle in both young adult and aged animals. Our immunoblot analyses indicated that protein expressions of HSP70 and HSP60 were not different between suspended and control muscles in both ages, whereas HSP27 protein content was increased in suspended muscle relative to control muscle only in young adult animals. Id2 and p53 protein contents were elevated in the cytosolic fraction of suspended muscle compared with the control muscle in both young and aged animals, but these changes were not found in the nuclear protein fraction. Furthermore, compared with young adult, aged muscles had a lower HSP70-1 mRNA content but higher HSP70-2 mRNA content and protein contents of Id2, p53, HSP70, and HSP27. These findings are consistent with the hypothesis that Id2 and p53 are responsive to unloading-induced muscle atrophy. Moreover, our data indicate that aging is accompanied with altered abundances of HSP70-1 and HSP70-2 mRNA, in addition to Id2, p53, HSP70, and HSP27 protein in rat gastrocnemius muscle.     

Enzymic properties of a Ca2+-dependent protease in rat ventral prostate: differences in distribution between lobes of the prostatic complex

Soluble extracts of rat ventral prostate contain a calcium-dependent, neutral thiol protease which is separated from an endogenous inhibitor by DEAE-cellulose chromatography. The Ca2+-dependent protease had a high calcium requirement (half maximal activation at 0.19 mM CaCl2), a pH optimum in the neutral range (pH 7-8), and it was inhibited by increased ionic strength (30% inhibition at 0.2 M NaCl). Leupeptin and antipain were strong inhibitors of the enzyme. Ca2+-activated protease activities of the coagulating gland (anterior prostate) were about 40% of those of the ventral prostate and were not detectable in the dorsolateral prostatic lobe. There was no difference in specific activities of this enzyme in chromatographed extracts of prostatic lobes from young sexually mature adults and 12 month old retired breeders. In addition, Ca2+-dependent protease activity was not detectable in chromatograms of rat ventral prostate and coagulating gland secretions. Therefore, the Ca2+-activated protease does not appear to be a secretory protein and probably acts at some intracellular site(s).     

Subcellular responses of p53 and Id2 in fast and slow skeletal muscle in response to stretch-induced overload.

Tumor suppressor p53 and inhibitor of DNA-binding/differentiation Id2 were examined after 7 or 21 days of wing weighting in fast patagialis (PAT) and slow anterior latissimus dorsi (ALD) wing muscles of young adult and old Japanese quails. The contralateral wing served as the intra-animal control. Seven days of loading increased PAT and ALD muscle weight by 28 and 96%, respectively, in young birds. PAT and ALD muscle weight was 49 and 179% greater, respectively, than control muscles after 21 days of loading in young birds. In aged birds, no PAT or ALD hypertrophy was found after 7 days of loading; however, PAT and ALD muscle weight increased by 29 and 102%, respectively, after 21 days of loading. Id2 protein in the nuclear muscle fraction increased in both PAT and ALD muscles from young adult and old birds that were loaded for 7 days and in ALD muscles after 21 days of loading relative to contralateral control muscles. Nuclear p53 protein was greater in 7- or 21-day loaded PAT and ALD muscles relative to control muscles in both age groups. Cytosolic Id2 and p53 protein contents were not changed in loaded PAT or ALD muscles relative to control muscles at any time point. These data suggest that nuclear, but not cytosolic, Id2 and p53 are responsive to stretch-induced muscle overload. Moreover, the attenuated ability of the aged skeletal muscle to achieve hypertrophy does not appear to be explained by the subcellular changes in Id2 and p53 content with overload.     

Morphology and protein patterns of honey bee drone accessory glands

We used light and transmission electron microscopy to examine the morphology of the accessory glands of immature and mature adult males of Apis mellifera L. We also made an electrophoretic analysis of the protein content of the mature gland. The glands of the immature male actively secrete a mucous substance that can be seen in the lumen of the gland of the mature male. This secretion stains with mercury bromophenol blue and with periodic acid-Schiff reaction, which stain glyconjugates. The protein content was higher in the lumen secretion than in the gland wall extracts. The electrophoresis patterns of the wall extracts were different from those of the secretion found in the gland lumen.     

Age-related changes in the expression and oxidation of bronchoalveolar lavage proteins in the rat

The incidence and severity of many lung diseases change with age. Some diseases, such as pneumonia, occur with increased frequency in children and the elderly. Proteins obtained by bronchoalveolar lavage (BAL) serve as the first line of defense against inhaled toxins and pathogens. Age-related changes in BAL protein expression and oxidative modification were examined in juvenile (1 mo), young adult (2 mo), and aged (18 mo) F344 rats using two-dimensional difference gel electrophoresis (2D-DIGE), matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-ToF/ToF) tandem mass spectrometry, and carbonyl immunoblotting. Using 2D-DIGE, we detected 563 protein spots, and MALDI-ToF/ToF identified 204 spots comprising 31 proteins; 21 changed significantly (17 increases) between juvenile and young adult or aged rats, but for 12 of these proteins, levels had a biphasic pattern, and levels in aged rats were less than in young adults. Relative carbonylation was determined by comparison of immunostaining with total protein staining on each oxidized protein blot. We found that aged rats had significantly increased oxidation in 13 proteins compared with juvenile rats. Many of the proteins altered in expression or oxidation level had functions in host defense, redox regulation, and protein metabolism. We speculate that low levels of expression of host defense proteins in juvenile rats and decreases in levels of these proteins between young adult and aged rats may predispose these groups to pneumonia. In addition, we have shown age-related increases in protein oxidation that may compromise host defense function in aged rats.     

Development and Ageing of the Rat Nigrostriatal Dopamine System Studied with Fast Cyclic Voltammetry

Fast cyclic voltammetry at carbon fibre microelectrodes was used to measure electrically stimulated dopamine release in the striatum of anaesthetised young, adult, and senescent Wistar rats. By alteration of stimulus parameters and by use of nomifensine, investigation of dopamine release, uptake, and compartmentalisation within the striatum was possible. The rate of dopamine release was highest in adult rats. No difference was observed between young and old animals. The size of the releasable (newly synthesised) dopamine pool was also largest in the adult group, again with no significant difference occurring between young and aged rats. The rate of dopamine uptake was highest in adult rats, although, when expressed as a function of dopamine release, young and aged rats showed proportionally greater uptake. Nomifensine (10 mg/kg i.p.) increased dopamine release by mobilising the inert storage pool to a greater extent in young than in adult rats, whereas the effect of the drug on uptake was similar in all age groups. The functional significance and possible explanation of these results are discussed.     

Angiotensin-converting enzyme (kinase II) in pituitary gland of spontaneously hypertensive rats

Angiotensin-converting enzyme (ACE) (kinase II; dipeptidyl carboxypeptidase, EC 3.4.15.1) activity was measured in pituitary gland of young (4-week-old) and adult (18-week-old) male, spontaneously hypertensive rats (SHR) and in age-matched normotensive male Wistar-Kyoto (WKY) control rats. In the three lobes of the pituitary gland ACE activity was significantly higher in young than in adult animals, in both SH and WKY rats. In the anterior lobe, ACE activity was lower in SHR when compared to age-matched Wistar-Kyoto controls. In contrast, ACE activity in the intermediate lobe of the pituitary gland was higher in SHR, and in particular in young animals. The observed differences between young WKY and SH rats in both the intermediate and anterior lobes did not appear to be due to a modified affinity of ACE for the substrate hippuryl-His-Leu, but to alterations in ACE maximal velocity or number of available molecules. No differences in ACE activity were detected between SHR and WKY rats in the posterior lobe. Total protein content was higher in the intermediate lobe and lower in the posterior lobe of young SHR when compared to normotensive controls. The present results suggest the possibility for a role of pituitary ACE in spontaneous (genetic) hypertension in rats.     

Effect of free radicals on adenosine A(2A) and dopamine D2 receptors in the striatum of young adult and aged rats

Parkinson's disease (PD) is a prevalent age-related motor dysfunction resulting from the hyperactivity of the indirect striatal pathway, which is controlled in an antagonistic manner by inhibitory dopamine D2 and facilitatory adenosine A(2A) receptors. Thus, dopamine precursors like l-DOPA are the standard therapy and A(2A) antagonists are now tested as anti-parkinsonians. Increased free radicals levels occur on aging and are proposed to be a contributing factor for PD. We now tested if free radicals affected A(2A) and D2 receptors in striatal membranes of young adult (2 months) and old (24 months) rats. The A(2A) receptor antagonist [3H]SCH 58261 bound to striatal membranes with a KD of 0.9 nM and a Bmax of 953 fmol/mg protein in young rats and with a KD of 0.8 nM and a Bmax of 725 fmol/mg protein in aged rats (24% decrease). The D2 receptor antagonist [3H]raclopride bound to striatal membranes with a KD of 4.0 nM and a Bmax of 598 fmol/mg protein in young rats and with a KD of 4.3 nM and a Bmax of 368 fmol/mg protein in aged rats (38% decrease). Exposure of striatal membranes to a free radical generation system (2 mM FeSO4 and 4 mM ascorbate) caused a similar decrease of [3H]SCH 58261 (35%) and [3H]raclopride (37%) binding in young adult rats but caused a greater decrease of [3H]SCH 58261 (49%) than of [3H]raclopride (20%) binding in aged rats. Thus, in aged rats, there is an unbalance of A(2A)/D2 receptor density favouring A(2A) receptors, which is restored on exposure to free radicals. This supports the hypothesis that the effectiveness of A(2A) receptor antagonists as anti-parkinsonians, demonstrated in young adult animals, may not be affected by a modified A(2A)/D2 receptor density in aged individuals suffering from exposure to increased free radical levels, as occurs in PD.     

Aging Contributes to Inflammation in Upper Extremity Tendons and Declines in Forelimb Agility in a Rat Model of Upper Extremity Overuse

We sought to determine if tendon inflammatory and histopathological responses increase in aged rats compared to young rats performing a voluntary upper extremity repetitive task, and if these changes are associated with motor declines. Ninety-six female Sprague-Dawley rats were used in the rat model of upper extremity overuse: 67 aged and 29 young adult rats. After a training period of 4 weeks, task rats performed a voluntary high repetition low force (HRLF) handle-pulling task for 2 hrs/day, 3 days/wk for up to 12 weeks. Upper extremity motor function was assessed, as were inflammatory and histomorphological changes in flexor digitorum and supraspinatus tendons. The percentage of successful reaches improved in young adult HRLF rats, but not in aged HRLF rats. Forelimb agility decreased transiently in young adult HRLF rats, but persistently in aged HRLF rats. HRLF task performance for 12 weeks lead to increased IL-1beta and IL-6 in flexor digitorum tendons of aged HRLF rats, compared to aged normal control (NC) as well as young adult HRLF rats. In contrast, TNF-alpha increased more in flexor digitorum tendons of young adult 12-week HRLF rats than in aged HRLF rats. Vascularity and collagen fibril organization were not affected by task performance in flexor digitorum tendons of either age group, although cellularity increased in both. By week 12 of HRLF task performance, vascularity and cellularity increased in the supraspinatus tendons of only aged rats. The increased cellularity was due to increased macrophages and connective tissue growth factor (CTGF)-immunoreactive fibroblasts in the peritendon. In conclusion, aged rat tendons were overall more affected by the HRLF task than young adult tendons, particularly supraspinatus tendons. Greater inflammatory changes in aged HRLF rat tendons were observed, increases associated temporally with decreased forelimb agility and lack of improvement in task success.     

Differential susceptibility of interneurons expressing neuropeptide Y or parvalbumin in the aged hippocampus to acute seizure activity

Acute seizure (AS) activity in old age has an increased predisposition for evolving into temporal lobe epilepsy (TLE). Furthermore, spontaneous seizures and cognitive dysfunction after AS activity are often intense in the aged population than in young adults. This could be due to an increased vulnerability of inhibitory interneurons in the aged hippocampus to AS activity. We investigated this issue by comparing the survival of hippocampal GABA-ergic interneurons that contain the neuropeptide Y (NPY) or the calcium binding protein parvalbumin (PV) between young adult (5-months old) and aged (22-months old) F344 rats at 12 days after three-hours of AS activity. Graded intraperitoneal injections of the kainic acid (KA) induced AS activity and a diazepam injection at 3 hours after the onset terminated AS-activity. Measurement of interneuron numbers in different hippocampal subfields revealed that NPY+ interneurons were relatively resistant to AS activity in the aged hippocampus in comparison to the young adult hippocampus. Whereas, PV+ interneurons were highly susceptible to AS activity in both age groups. However, as aging alone substantially depleted these populations, the aged hippocampus after three-hours of AS activity exhibited 48% reductions in NPY+ interneurons and 70% reductions in PV+ interneurons, in comparison to the young hippocampus after similar AS activity. Thus, AS activity-induced TLE in old age is associated with far fewer hippocampal NPY+ and PV+ interneuron numbers than AS-induced TLE in the young adult age. This discrepancy likely underlies the severe spontaneous seizures and cognitive dysfunction observed in the aged people after AS activity.     

Increase in the Number, G Protein Coupling, and Efficiency of Facilitatory Adenosine A2A Receptors in the Limbic Cortex, but not Striatum, of Aged Rats

Adenosine's effects result from a balanced activation of inhibitory A1 and facilitatory A2A receptors. Because in aged animals there is an increased number of A2A receptors, we now compared the efficiency of A2A receptors in cortical and striatal preparations of young adult (6-week-old) and aged (2-year-old) rats. In cortical, in contrast to striatal, membranes from aged rats, A2A receptors were more tightly coupled to G proteins, because 5'-guanylylimidodiphosphate (100 microM) increased by 321% the Ki of the A2A agonist CGS21680 as a displacer of binding of the A2A antagonist [3H]ZM241385 (1 nM), compared with a 112% increase in young rats. In cortical slices, CGS21680 (30-1,000 nM) was virtually devoid of effect on cyclic AMP accumulation in young rats but increased cyclic AMP accumulation with an EC50 of 153 nM in aged rats, whereas the efficiency of CGS21680 was similar in striatal slices of young and aged rats. CGS21680 (30 nM) was virtually devoid of effect on acetylcholine release from hippocampal CA1 slices of young rats but caused a 55% facilitation in aged rats. These results show that the number of A2A receptors, their coupling to G proteins, and their efficiency are enhanced in the limbic cortex of aged rats, suggesting a greater involvement of facilitation in adenosine responses.     

Development and Applications of a Solid-Phase Radioimmunoassay for the P0 Protein of Peripheral Myelin

This is the first report of a quantitative radioimmunoassay for PO. The assay uses antigen-coated plastic microwells, with antibody binding detected by 125I-labeled protein A. Either peripheral myelin proteins or purified PO may be used as the antigen. Optimal extraction of tissue samples for PO immunoassay requires careful attention to the sodium dodecyl sulfate-to-protein ratio. Sodium dodecyl sulfate interference with antibody binding can be minimized by adding an excess of nonionic detergent and carrier protein to the incubation buffer. This method allows the detection of 0.8 ng of PO (20 ng/ml). Results from this assay showed little or no immunoreactivity in extracts of brain, centra myelin, liver, purified myelin basic proteins, cultured, purified secondary Schwann cells, or membrane preparations from these cells. PO was clearly detectable in Schwann cell cultures from 3- to 4-day-old rats at 12-18 h after dissociation (4% of the level in adult sciatic nerve) and in extracts of one-day-old rat sciatic nerve (2% of the level in adult nerve). Myelin basic protein radioimmunoassays showed that the ratio of PO to myelin basic protein is essentially constant in extracts of sciatic nerve from ne-day-old, four-day-old, and young adult rats. Another result was that PO levels are reduced in the trembler mouse sciatic nerve.     

Immunolocalization of allatostatin-like neuropeptides and their putative receptor in eyestalks of the tiger prawn, Penaeus monodon

Allatostatin (AST)-like immunoreactivity (IR) was localized in the eyestalk of Penaeus monodon by immunohistochemistry using four anti-AST antibodies. Depending on the antisera, AST-like immunoreactivity was detected in neuronal bodies of the lamina ganglionalis, cell bodies anterior to the medulla externa and cell bodies on the anterior and posterior of the medulla terminalis. Neuronal processes in neuropiles of the medulla externa, medulla terminalis, sinus gland and nerve fibers in the optic nerve were also recognized. No IR in cell bodies or in nerve fibers was found in the medulla interna. Strong AST-like immunoreactivity was found in hundreds of cells of the X organ. The localization of AST-like peptides suggests that they function as neurotransmitters and/or neuromodulators. Antiserum to the Drosophila AST receptor (Dar-2) recognized a single protein in P. monodon eyestalk protein extracts that was identical in size to that found in Drosophila protein extracts. Using this antiserum the putative P. monodon AST receptor was localized to the sinus gland in both juvenile and adult eyestalks. To our knowledge this is the first demonstration of a neuropeptide receptor localized to the crustacean sinus gland. This suggests that ASTs may function directly on the sinus gland as a neuromodulator. In juvenile eyestalks, the putative AST receptor was also localized to neuronal X organ cells of the medulla terminalis in males but not in females. The significance of this sex-specific receptor localization is unclear but emphasizes that ASTs function within the nervous system of the eyestalk.     

Age-related apoptotic responses to stretch-induced hypertrophy in quail slow-tonic skeletal muscle

In the present study, we examined the responses of apoptosis and apoptotic regulatory factors to muscle hypertrophy induced by stretch overload in quail slow-tonic muscles. The wings from one side of young and aged Japanese quails were loaded by attaching a tube weight corresponding to 12% of the bird's body weight for 7 or 21 days. Muscle from the contralateral side served as the intraanimal control. Relative to the intraanimal contralateral control side, the muscle wet weight increased by 96% in young birds, whereas the muscle weight gain in aged birds was not significant after 7 days of loading. After 21 days of loading, muscle weight significantly increased by 179% and 102% in young and aged birds, respectively. Heat shock protein (HSP)72 and HSP27 protein contents in the loaded sides were higher than on the control sides exclusively in young birds after 7 days of loading. Compared with the contralateral control muscle, the extent of apoptotic DNA fragmentation and the total cytosolic apoptosis-inducing factor protein content were reduced in all loaded muscles except for the 7-day-loaded muscles from the aged birds. Bax protein content was diminished in the loaded muscle relative to the control side from all groups, whereas Bcl-2 protein content was reduced in the young and aged muscles after 21 days of loading. The total cytosolic cytochrome c protein content was decreased and the X chromosome-linked inhibitor of apoptosis protein content was elevated in 7- and 21-day-loaded muscles relative to the intraanimal control muscle from young birds. Furthermore, after 7 days of loading the muscles of aged birds, H₂O₂ content and the total cytosolic protein content of second mitochondrial activator of caspases/direct inhibitor of apoptosis-binding protein with low isoelectric point were elevated compared with the intraanimal control side. These data suggest that stretch overload-induced muscle hypertrophy is associated with changes in apoptosis in slow-tonic skeletal muscle. Moreover, discrepant apoptotic responses to muscle overload in young and aged muscles may account in part for the age-related decline in the capability for muscle hypertrophy. aging; sarcopenia; Bcl-2; Bax; heat shock proteins; apoptosis-inducing factor     

Comparison of Expression of Inflammatory Cytokines in the Spinal Cord Between Young Adult and Aged Beagle Dogs

Aging is an inevitable process that occurs in the whole body system accompanying with many functional and morphological changes. Inflammation is known as one of age-related factors, and inflammatory changes could enhance mortality risk. In this study, we compared immunoreactivities of inflammatory cytokines, such as interleukin (IL)-2 (a pro-inflammatory cytokine), its receptor (IL-2R), IL-4 (an anti-inflammatory cytokine), and its receptor (IL-4R) in the cervical and lumbar spinal cord of young adult (2–3 years old) and aged (10–12 years old) beagle dogs using immunohistochemistry and western blotting. IL-2 and IL-2R-immunoreactive nerve cells were found throughout the gray matter of the cervical and lumbar spinal cord of young adult and aged dogs. In the spinal cord neurons of the aged dog, immunoreactivity and protein levels were apparently increased compared with those in the young adult dog. Change patterns of IL-4- and IL-4R-immunoreactive cells and their protein levels were also similar to those in IL-2 and IL-2R; however, IL-4 and IL-4R immunoreactivity in the periphery of the neuronal cytoplasm in the aged dog was much stronger than that in the young adult dog. These results indicate that the increase of inflammatory cytokines and their receptors in the aged spinal cord might be related to maintaining a balance of inflammatory reaction in the spinal cord during normal aging.