Age-dependent changes in 24-hour rhythms of catecholamine content and turnover in hypothalamus, corpus striatum and pituitary gland of rats injected with Freund's adjuvant.

BACKGROUND: Little information is available on the circadian sequela of an immune challenge in the brain of aged rats. To assess them, we studied 24-hour rhythms in hypothalamic and striatal norepinephrine (NE) content, hypothalamic and striatal dopamine (DA) turnover and hypophysial NE and DA content, in young (2 months) and aged (18-20 months) rats killed at 6 different time intervals, on day 18th after Freund's adjuvant or adjuvant's vehicle administration. RESULTS: Aging decreased anterior and medial hypothalamic NE content, medial and posterior hypothalamic DA turnover, and striatal NE concentration and DA turnover. Aging also decreased NE and DA content in pituitary neurointermediate lobe and augmented DA content in the anterior pituitary lobe. Immunization by Freund's adjuvant injection caused: (i) reduction of DA turnover in anterior hypothalamus and corpus striatum; (ii) acrophase delay of medial hypothalamic DA turnover in old rats, and of striatal NE content in young rats; (iii) abolition of 24-h rhythm in NE and DA content of neurointermediate pituitary lobe, and in DA content of anterior lobe, of old rats. CONCLUSIONS: The decline in catecholamine neurotransmission with aging could contribute to the decrease of gonadotropin and increase of prolactin release reported in similar groups of rats. Some circadian responses to immunization, e.g. suppression of 24-h rhythms of neurointermediate lobe NE and DA and of anterior lobe DA were seen only in aged rats.

Effect of melatonin on 24h changes in plasma protein levels during the preclinical phase of Freund's adjuvant arthritis in rats.

The 24h rhythms in plasma protein concentration were examined in rats on the third day after injection of Freund's complete adjuvant or adjuvant's vehicle, performed 3h after light on. In rats treated with adjuvant's vehicle, peak values of albumin and gamma globulin occurred during the nocturnal activity span (P < .02 and P < .0001, respectively), while those of alpha-1, alpha-2, and beta globulins were found late during the rest span (P < .002, P < .0001, and P < .0004, respectively). Freund's adjuvant administration abolished temporal changes in plasma albumin and beta globulin levels. It also decreased the amplitude of daily changes in alpha-1 and alpha-2 globulin (P < .05) and diminished mean values of alpha-2 globulin (P < .01). Pretreatment of rats with melatonin (30 microg daily) for 11 days, 11h after light on, counteracted mycobacterial adjuvant-induced suppression of the 24h rhythms in albumin and alpha-1, alpha-2, and beta globulins. The results further support the existence of preventive properties of a pharmacological dose of melatonin in situations in which a lost of circadian rhythmicity is expected.

Aging-induced changes in 24-h rhythms of mitogenic responses, lymphocyte subset populations and neurotransmitter and amino acid content in rat submaxillary lymph nodes during Freund's adjuvant arthritis.

In young (two months) and aged (18 months) male rats injected s.c. with Freund's adjuvant or adjuvant's vehicle 18 days earlier, 24-h variations in mitogenic responses, lymphocyte subsets and monoamine and amino acid content were examined in submaxillary lymph nodes. Mitogenic responses to concanavalin A (Con A) and lipopolysaccharide (LPS) were higher during the light phase of daily photoperiod. Old rats exhibited a suppressed or impaired mitogenic response to Con A but not to LPS. Acrophases of 24-h rhythm in lymphocyte subset populations in submaxillary lymph nodes were: 18:37-19:44h (B cells), 09:00-10:08h (T and CD4(+) cells) and 12:19-15:58h (CD8(+) cells). Aging augmented B cells and decreased T, CD4(+) and CD8(+) cells. Significant correlations were found between Con A activity and T cells, between lymph node 5HT content and B, T and CD8(+) lymphocytes, and between lymph node 5HT and taurine and GABA content. Aging increased lymph node 5HT content but did not modify NE content. Lymph node concentration of aspartate, glutamate and taurine was higher at night while that of GABA attained peak values at late afternoon. Old rats injected with Freund's adjuvant showed a higher mean value (glutamate) and smaller amplitude (glutamate, taurine) than their respective young controls. The results further document the effects of aging on the chronobiology of the immune system.

Effect of superior cervical ganglionectomy on 24-h variations in hormone secretion from the anterior hypophysis and in hypothalamic monoamine turnover during the preclinical phase of Freund's adjuvant arthritis in rats.

The effect of superior cervical ganglionectomy (SCGx) on 24-h rhythms of circulating adrenocorticotropic hormone (ACTH), growth hormone (GH), prolactin and luteinizing hormone (LH) and of hypothalamic noradrenaline content and dopamine and serotonin turnover, was assessed in rats 3 days after administering Freund's complete adjuvant. In sham-operated rats, Freund's adjuvant injection increased serum ACTH without affecting its diurnal rhythmicity. SCGx, performed 10 days earlier, suppressed 24-h rhythmicity and augmented mean values of circulating ACTH. A depressive effect of immunization on GH release was found in both sham-operated and SCGx rats. GH concentrations did not exhibit diurnal rhythmicity and decreased after immunization. Time-of-day-related changes in serum prolactin were significant for all examined groups, except for SCGx-immunized rats. Freund's adjuvant administration augmented prolactin secretion. Daily changes in serum LH concentration and a decrease after immunization were found in both sham-operated and SCGx rats. SCGx: (i) counteracted inhibition of daily variations of noradrenaline content in medial hypothalamus of Freund's adjuvant-injected rats; (ii) decreased anterior hypothalamic dopamine turnover and augmented it in the medial hypothalamus; (iii) lowered amplitude of serotonin turnover rhythm in medial hypothalamus. The data indicate that several early changes in levels and 24-h rhythms of circulating ACTH and prolactin, and in hypothalamic noradrenaline content and dopamine and serotonin turnover, were modified by a previous SCGx in Freund's adjuvant-injected rats.

Effect of melatonin on bone metabolism in ovariectomized rats.

To assess the effect of pharmacological dose of melatonin on bone metabolism in ovariectomized rats, urinary deoxypyridinoline (a marker of bone resorption) and calcium excretion, circulating levels of calcium, phosphorus and bone alkaline phosphatase activity (a marker of bone formation), and bone mineral density (BMD), mineral content (BMC) and bone area (BA) of total body, were measured in adult rats for up to 60 days after surgery. Rats received melatonin in the drinking water (25 microg/ml water) or drinking water alone. Urinary deoxypyridinoline increased significantly after ovariectomy by 51% (30 days after surgery) and by 47% (60 days after surgery). The increase in urinary deoxypyridinoline found 30 days after ovariectomy was not observed in melatonin-treated rats. Urinary calcium concentration was similar in the 4 experimental groups studied, as was the circulating calcium concentration at every time interval examined. Fifteen days after surgery, a significant increase in serum phosphorus and bone alkaline phosphatase levels occurred in ovariectomized rats receiving melatonin as compared to their controls. Sixty days after surgery BMD, BMC and BA decreased significantly in ovariectomized rats, an effect not modified by melatonin. Serum estradiol decreased significantly by 30 days after ovariectomy to attain values close to the limit of detection of the assay by 60 days after ovariectomy. The results support the conclusion that a pharmacological amount of melatonin modifies bone remodeling after ovariectomy and that the effect may need adequate concentrations of estradiol.

Age-dependent changes in 24-hour rhythms of thymic and circulating growth hormone and adrenocorticotropin in rats injected with Freund's adjuvant.

OBJECTIVE: To analyze the 24-hour changes in thymic and serum concentration of growth hormone (GH) and adrenocorticotropin (ACTH) and their correlation with thymic concentrations of glutamate, aspartate, taurine and GABA in young and old rats during the acute phase of adjuvant's arthritis. METHODS: Young (50-day-old) and old (18-month-old) rats were injected subcutaneously with Freund's adjuvant or its vehicle (paraffin oil containing 15% mannide monooleate). Eighteen days later, they were killed at six different time intervals throughout a 24-hour cycle. Serum and thymic levels of GH and ACTH were measured by radioimmunoassay. Thymic amino acid concentration was measured by HPLC. A quantitative assessment of arthritis was made in an independent group of rats by plethysmography. RESULTS: Old rats injected with Freund's adjuvant exhibited fewer clinical signs of inflammation than young rats. Significant 24-hour changes in thymic and serum GH occurred, except for serum GH in adjuvant's vehicle-treated old rats. Aging augmented thymic GH and decreased serum GH. Immunization with Freund's adjuvant did not modify GH concentration. Thymic and serum concentration of GH correlated negatively. Thymic ACTH varied significantly over 24 h with maxima during the dark phase, except in Freund's adjuvant-treated young rats. Maximal serum ACTH levels occurred in the late afternoon except in Freund's adjuvant-treated old rats which showed maxima at night. Immunization with Freund's adjuvant augmented thymic and circulating concentrations of ACTH. Thymic and serum concentration of ACTH correlated positively. Thymic concentration of glutamate, aspartate and taurine decreased in aged rats and correlated significantly with thymic ACTH. CONCLUSION: The results support the existence of a thymic compartment of GH and ACTH that may be independently regulated.

Auditory deprivation modifies biological rhythms in the golden hamster.

To assess to what extent auditory sensory deprivation affects biological rhythmicity, sleep/wakefulness cycle and 24 h rhythm in locomotor activity were examined in golden hamsters after bilateral cochlear lesion. An increase in total sleep time as well as a decrease in wakefulness (W) were associated to an augmented number of W episodes, as well as of slow wave sleep (SWS) and paradoxical sleep (PS) episodes in deaf hamsters. The number of episodes of the three behavioural states and the percent duration of W and SWS increased significantly during the light phase of daily photoperiod only. Lower amplitudes of locomotor activity rhythm and a different phase angle as far as light off were found in deaf hamsters kept either under light-dark photoperiod or in constant darkness. Period of locomotor activity remained unchanged after cochlear lesions. The results indicate that auditory deprivation disturbs photic synchronization of rhythms with little effect on the clock timing mechanism itself.

Effect of melatonin treatment on 24-h variations in responses to mitogens and lymphocyte subset populations in rat submaxillary lymph nodes.

Wistar male rats were injected s.c. with melatonin (30 microg) or vehicle, 1 h before lights off, for 11 days. Ten days after beginning melatonin treatment, rats received Freund's complete adjuvant or its vehicle s.c., and after 2 days, they were sacrificed at six different time intervals throughout a 24-h cycle. The mitogenic effect of lipopolysaccharide (LPS) and concanavalin A (Con A), the activity of ornithine decarboxylase (ODC) and the relative size of lymphocyte subset populations were measured in submaxillary lymph nodes. In control rats, the mitogenic effects of LPS and Con A and ODC activity peaked during the afternoon. Injection of Freund's adjuvant induced a 10-h shift in the diurnal rhythm of the mitogenic effect of LPS to attain maximal values at night. Melatonin pretreatment blunted the daily variations in the mitogenic activity of Con A or LPS and, when given to Freund's adjuvant-injected rats, augmented mesor and amplitude of diurnal rhythm in ODC activity. Maxima in B cell number occurred at night whereas those of T and B-T cell number occurred during the afternoon. During the early phase of immunization tested, the number of B cells augmented and the amplitude of its diurnal rhythmicity increased both after immunization and following melatonin pretreatment. Maxima of 24-h rhythms in CD4+ and CD4+/CD8+ cell populations occurred during the afternoon while those of CD8+ cells occurred at late night. Melatonin significantly augmented CD4+ cell number and decreased CD8+ cell number; it therefore augmented the CD4+:CD8+ ratio. The results suggest that pretreatment with a pharmacological dose of melatonin exerts immunomodulating effects at an early, preclinical, phase of Freund's adjuvant-induced arthritis in rats.

Psychoimmune neuroendocrine integrative mechanisms revisited.

This review analyzes recent publications on the topic of psycho-immune-neuroendocrine integrative mechanisms. Results on the role of cytokines in cognitive processes and in a major neuroendocrine event, i.e. the release of gonadotropin-releasing hormone, are discussed, as are the effects of cytokines on central neurotransmission. The control of immune responses by local sympathetic nerves, a major pathway in neuroimmune communication, is discussed. This review also updates information indicating that melatonin is a circulating signal affecting the periodic organization of the immune response.

Effect of melatonin treatment on 24-hour rhythms of serum ACTH, growth hormone, prolactin, luteinizing hormone and insulin in rats injected with Freund's adjuvant.

The effect of melatonin injection on Freund's adjuvant-induced changes in levels and 24-hr rhythms of circulating ACTH, growth hormone (GH), prolactin (PRL), luteinizing hormone (LH), and insulin was assessed in rats. Animals received subcutaneous (s.c.) injections of melatonin (30 microg) or vehicle, 1 hr before lights off for 12 days. Ten days after melatonin treatment, they were injected with Freund's complete adjuvant or its vehicle s.c., and after 3 days, rats were killed at six different time intervals throughout a 24-hr cycle to measure the different hormones by radioimmunoassay (RIA). Following Freund's adjuvant injection, an increase in serum ACTH, with maintenance of ACTH diurnal rhythm was found. Acrophases of the ACTH rhythm varied from 13:39 to 17:12 hr and the amplitude of rhythm was augmented after immunization. In immunized rats, melatonin treatment increased the amplitude of serum ACTH rhythm. For GH, a depressive effect of immunization on circulating levels, together with absence of diurnal rhythmicity were found. Immunization augmented circulating PRL, while conserving its diurnal rhythmicity. Melatonin-injected rats showed significant diurnal variations of serum PRL after immunization only. Acrophases of the serum PRL rhythm varied from 19:37 to 22:04 hr. Immunization decreased circulating LH and suppressed its 24-hr rhythmicity pattern. The effect of immunization on LH was counteracted by melatonin injection. Acrophases of serum LH rhythm varied from 00:44 to 03:53 hr. Significant effects of immunization and time of day on circulating insulin were detected; immunization increased serum insulin levels with a shift in acrophase from early afternoon to midnight. The data indicate that several early changes in levels and 24-hr rhythms of circulating ACTH, PRL, and LH in Freund's adjuvant-injected rats were sensitive to treatment with pharmacological amounts of melatonin.

Twenty-four hour rhythms of hypothalamic corticotropin-releasing hormone, thyrotropin-releasing hormone, growth hormone-releasing hormone and somatostatin in rats injected with Freund's adjuvant.

The effect of Freund's adjuvant injection on 24-hour variation of hypothalamic corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), GH-releasing hormone (GRH) and somatostatin levels was examined in adult rats kept under light between 0800 and 2000 h daily. Groups of rats receiving Freund's complete adjuvant or its vehicle 3 days before sacrifice were killed at six different time intervals throughout a 24-hour cycle. In the median eminence, adjuvant vehicle-injected rats exhibited significant 24-hour variations for the four hormones examined, with maxima at noon. These 24-hour rhythms were inhibited or suppressed by Freund's adjuvant injection. In the anterior hypothalamus of adjuvant vehicle-treated rats, CRH content peaked at 1600 h, while two peaks were found for TRH and GRH levels, i.e., at 2400-0400 h and 1600 h. Freund's adjuvant injection suppressed 24-hour rhythm of anterior hypothalamic CRH, TRH and GRH content and uncovered a peak in anterior hypothalamic somatostatin levels at 0400 h. In the medial hypothalamus of adjuvant vehicle-treated rats, significant 24-hour variations were detectable for TRH (peaks at 1600 and 2400 h) and somatostatin (peak at 2400 h) which disappeared after Freund's adjuvant injection. In the posterior hypothalamus of adjuvant vehicle-treated rats, two peaks were apparent for CRH, TRH and somatostatin levels, i.e. at 1600 h and 2400-0400 h, this hormonal profile remaining unmodified after Freund's adjuvant administration. The administration of the immunosuppressant drug cyclosporine (5 mg/kg, 5 days) impaired the depressing effect of Freund's adjuvant injection on CRH, TRH and somatostatin content in median eminence, but not that on GRH. In the anterior hypothalamus, cyclosporine generally prevented the effect of immunization on hormone levels an revealed a second maximum in TRH at 0400 h. Cyclosporine also restored 24-hour variations in TRH and somatostatin levels of medial hypothalamus of Freund's adjuvant-injected rats but was unable to modify them in the posterior hypothalamus. The results further support the existence of a significant effect of immune-mediated inflammatory response at an early phase after Freund's adjuvant injection on hypothalamic levels which was partially sensitive to immunosuppression by cyclosporine.

Effect of melatonin on 24-hour rhythms of ornithine decarboxylase activity and norepinephrine and acetylcholine synthesis in submaxillary lymph nodes and spleen of young and aged rats.

Young (50 days old) and old (18 months old) Sprague-Dawley rats were injected with mycobacterial Freund's adjuvant to produce an inflammatory disease of the joints and were studied the day before, and on days 6, 12 and 18 after injection. At every postinjection interval examined, old rats had significantly lower circadian amplitudes of pineal melatonin content. On day 18 of arthritis development, decreased levels of pineal melatonin were also seen in young rats. A second study, carried out 18 days after the injection of Freund's complete adjuvant and after 17 daily injections of 10 or 100 microg of melatonin in the evening, indicated that melatonin treatment restored the inflammatory response in old rats (assessed plethysmographically in hind paws) to the level found in young animals. In young rats, an inflammation-promoting effect of 100 microg melatonin could be demonstrated. As a consequence of the immune reaction, submaxillary lymph node and splenic ornithine decarboxylase activity (an index of lymph cell proliferation) augmented significantly, with acrophases of 24-hour rhythms in the afternoon for lymph nodes or in the morning for spleen. Mesor and amplitude of ornithine decarboxylase rhythm were lowest in old rats, while melatonin injection generally augmented its amplitude. Lymph node and splenic tyrosine hydroxylase activity (a presynaptic adrenergic marker) reached maximal values during early night hours while maximal values of [3H]acetylcholine synthesis (a presynaptic cholinergic marker) occurred during the afternoon in lymph nodes. Amplitude and mesor of these rhythms were lowest in old rats, an effect generally counteracted by melatonin treatment. The results suggest that inflammation is accompanied by an age-dependent, significant depression of pineal melatonin synthesis during adjuvant-induced arthritis and a decreased amplitude of the circadian rhythm of immune cell proliferation and autonomic activity in lymph nodes and spleen. These effects are counteracted by injection of melatonin, mainly in old rats.

Circadian rhythms in adenohypophysial hormone levels and hypothalamic monoamine turnover in mycobacterial-adjuvant-injected rats.

The effect of Freund's adjuvant injection on 24-hour variation in circulating ACTH, prolactin, growth hormone (GH) and thyroid-stimulating hormone (TSH) levels, and of hypothalamic norepinephrine (NE) content and dopamine (DA) and serotonin (5HT) turnover was examined in adult rats. In control rats, serum ACTH and prolactin exhibited peak values at the light-dark transition while the maximum in TSH was found in the late afternoon. GH levels did not vary on a 24-hour basis. In Freund's-adjuvant-injected rats, 24-hour variations in TSH levels became blunted while 24-hour variations in prolactin and ACTH persisted. Freund's adjuvant treatment augmented serum ACTH and prolactin levels, and decreased GH and TSH levels. Hypothalamic NE content, and turnover of DA and 5HT varied on a 24-hour basis in rats receiving adjuvant's vehicle. The NE content of the anterior, medial and posterior hypothalamus peaked at 04.00 h, while that of the median eminence attained its maximum at 16.00-20.00 h. Maxima in hypothalamic DA and 5HT turnover occurred at 04.00 h regardless of the region examined. In Freund's-adjuvant-injected rats, reduced amplitude of daily variations of NE content in the median eminence and anterior and medial hypothalamus, as well as a phase advance in the 24-hour rhythm of the posterior hypothalamic NE content were seen. Mycobacterial adjuvant injection also reduced the amplitude of circadian rhythm in hypothalamic 5HT turnover, shifted the maximum in median eminence DA turnover towards light-dark transition, and decreased the amplitude of DA turnover rhythm in the anterior, medial and posterior hypothalamus. Administration of the immunosuppressant drug cyclosporine restored the augmented ACTH and prolactin levels and the depressed GH and TSH levels found in Freund's-adjuvant-injected rats. Cyclosporine was also effective to restore 24-hour rhythmicity of serum ACTH and TSH, but not of prolactin levels. Immunosuppression restored rhythmicity of NE content and of DA and 5HT turnover in anterior, medial and posterior hypothalamic regions. Cyclosporine did not modify the effect of Freund's adjuvant on median eminence but in was able to counteract the changes in the DA and 5HT turnover in the median eminence found after immunization. The results are in accord with a significant effect of immune-mediated inflammatory response at an early phase after Freund's adjuvant injection on ACTH, GH, prolactin and TSH release mechanisms, which was partially sensitive to immunosuppression induced by cyclosporine.

Effect of pinealectomy, superior cervical ganglionectomy, or melatonin treatment on 24-hour rhythms in ornithine decarboxylase and tyrosine hydroxylase activities of rat spleen.

Diurnal variations in splenic ornithine decarboxylase and tyrosine hydroxylase activities were examined in rats subjected to pinealectomy, bilateral superior cervical ganglionectomy, or their respective sham operations. Rats were treated with Freund's complete adjuvant or its vehicle 2 days before sacrifice. After immunization, splenic ornithine decarboxylase activity was augmented 5-6-fold. In both immunized and nonimmunized sham-operated rats, significant diurnal variations in ornithine decarboxylase activity were detectable, with a maximum at early morning, acrophases after Cosinor analysis varying from 0845 to 1048h. In pinealectomized or superior cervical ganglionectomized, immunized rats, ornithine decarboxylase activity attained values 22-27% lower than those of immunized sham-operated controls, while amplitude decreased significantly by 27-30%. Administration of melatonin (30 microg/animal s.c. at late evening for 11 days in immunized rats) significantly augmented mesor levels of splenic ornithine decarboxylase activity and increased the amplitude of the diurnal rhythm both in pinealectomized and in superior cervical ganglionectomized rats. Melatonin treatment also augmented rhythm mesor in immunized, sham-ganglionectomized rats, as well as rhythm amplitude in immunized and nonimmunized, sham-ganglionectomized rats. Splenic tyrosine hydroxylase activity attained its maximum at late afternoon and early night, with acrophases varying from 1800 to 2023h. Immunization significantly increased mesor values of splenic tyrosine hydroxylase activity, whereas neither pinealectomy nor superior cervical ganglionectomy affected circadian rhythm parameters. Melatonin treatment augmented mesor values of tyrosine hydroxylase rhythm and increased its amplitude in pinealectomized, ganglionectomized, or sham-operated rats. The results are compatible with the view that the pineal gland plays a role in circadian changes of immune responsiveness in rat spleen via an immunopotentiating effect of melatonin on splenic cell proliferation.

Diurnal changes in cyclosporine effect on ornithine decarboxylase and noradrenergic and cholinergic activities in submaxillary lymph nodes.

Diurnal changes in cyclosporine efficacy to affect ornithine decarboxylase activity, [3H]norepinephrine uptake and [3H]choline conversion into [3H]acetylcholine were examined in rat submaxillary lymph nodes. Cyclosporine (5 or 20 mg/kg) caused a dose-dependent decrease in lymph node ornithine decarboxylase, being active at 5 or 20 mg/kg in Freund's adjuvant-treated rats, and at 20 mg/kg in rats treated with the adjuvant's vehicle. In immunized rats the lower cyclosporine dose was ineffective when injected during the night. Cyclosporine increased lymph node [3H]norepinephrine uptake dose dependently, with significant differences between the 20 mg/kg dose and controls in vehicle-treated rats and between 5 or 20 mg/kg and controls in Freund's adjuvant-treated rats. In immunized rats, 5 mg/kg cyclosporine increased [3H]norepinephrine uptake when injected at 13:00 or 17:00 h. Both doses of cyclosporine augmented lymph node synthesis of [3H]acetylcholine to a similar extent. In immunized and non-immunized rats cyclosporine suppressed the diurnal rhythm of lymph node adrenergic and cholinergic activity found in controls. After unilateral sympathetic denervation (by superior cervical ganglionectomy) and/or unilateral parasympathetic decentralization (by chorda tympani section), cyclosporine (5 mg/kg) decreased Freund's adjuvant-induced activation of lymph node ornithine decarboxylase when injected at 17:00 or 01:00 h. On the sham-operated side, cyclosporine was effective when injected at 17:00 h only. Decentralization, or a combined ganglionectomy plus decentralization, decreased lymph node ornithine decarboxylase activity. The results active regulation of the effects of cyclosporine in submaxillary lymph nodes by local autonomic nerves.

Diurnal rhythm in ornithine decarboxylase activity and noradrenergic and cholinergic markers in rat submaxillary lymph nodes.

Diurnal variations in lymph node ornithine decarboxylase activity were examined in submaxillary lymph nodes of rats injected with Freund's complete adjuvant or its vehicle. After immunization, lymph node ornithine decarboxylase activity increased by about 10-fold. Both in immunized and non-immunized rats, a significant diurnal variation in ornithine decarboxylase activity was found, with a maximal activity at early (i.e. 13.00 h, vehicle) or late afternoon (i.e. 17.00 h, Freund's adjuvant). Injection of Freund's adjuvant during daylight or at night resulted in similar day-night differences in submaxillary lymph node ornithine decarboxylase activity. In rats subjected to the sympathetic postganglionic denervation (by ipsilateral superior cervical ganglionectomy) or the preganglionic parasympathetic decentralization (by chorda tympani section) of submaxillary lymph nodes, nyctohemeral variations in ornithine decarboxylase were still present, showing a maximum at 17.00 h. Superior cervical ganglionectomy augmented lymph node ornithine decarboxylase while chorda tympani section decreased it. When a unilateral superior cervical ganglionectomy plus chorda tympani section was performed, the diurnal changes in ornithine decarboxylase were abolished. [3H]Norepinephrine uptake and tyrosine hydroxylase activity attained their maxima in submaxillary lymph nodes at early night. After immunization, these two presynaptic indicators of sympathetic activity in submaxillary lymph nodes augmented significantly. Neuronal [3H]choline uptake and [3H]choline conversion into acetylcholine (two indicators of cholinergic activity) also augmented in lymph nodes of rats injected with Freund's adjuvant. In immunized rats, maxima in [3H]choline uptake and [3H]acetylcholine synthesis were found at 13.00-17.00 h while in non-immunized rats, a maximum in acetylcholine synthesis was found at 17.00 h. The results are compatible with the view that the autonomic nervous system plays a role in circadian changes of immune responsiveness in lymphoid tissue and that a significant augmentation of presynaptic autonomic activity takes place during immunization in lymphoid tissue.

Diurnal rhythms in ornithine decarboxylase activity and norepinephrine and acetylcholine synthesis and acetylcholine synthesis of rat submaxillary lymph nodes: effect of pinealectomy, superior cervical ganglionectomy and melatonin replacement.

The effect of pinealectomy, superior cervical ganglionectomy and melatonin replacement on diurnal variations in submaxillary lymph node ornithine decarboxylase activity, tyrosine hydroxylase activity and [3H]choline conversion to [3H]acetylcholine were examined in rats subjected to pinealectomy, bilateral superior cervical ganglionectomy or their respective sham-operations, and treated with Freund's complete adjuvant or its vehicle. In both immunized and nonimmunized sham-operated rats, significant diurnal variations in ornithine decarboxylase activity were detectable, with a maximum at 13.00 h (vehicle) or at 17.00 h (Freund's adjuvant). In rats subjected to pinealectomy, ornithine decarboxylase activity decreased by about half, still exhibiting significant diurnal variations with a maximum at 13.00 h. Abolition of circadian rhythmicity and depression of ornithine decarboxylase activity to about one third of controls were found in submaxillary lymph nodes of bilaterally superior cervical ganglionectomized rats. Administration of melatonin (30 micrograms/animal) in the late evening during 11 days counteracted the depressed levels and suppressed the amplitude of diurnal rhythmicity of ornithine decarboxylase in pinealectomized or bilaterally superior cervical ganglionectomized rats, as well as augmented enzyme activity in sham-operated controls. The amplitude and mean levels of 24-hour rhythms in submaxillary lymph node tyrosine hydroxylase activity and [3H]choline conversion to acetylcholine (that attained their maxima at 21.00-1.00 and 13.00-17.00 h, respectively) decreased significantly after pinealectomy, these effects being significantly counteracted by melatonin injection. Melatonin augmented tyrosine hydroxylase activity and acetylcholine synthesis in sham-pinealectomized rats. The results are compatible with the view that the pineal gland plays a role in circadian changes of immune responsiveness in lymphoid tissue via an immunopotentiating effect of melatonin on lymph node cell proliferation.

Cyclosporine effect on ornithine decarboxylase activity in rat submaxillary lymph nodes. Modulation by parasympathetic nerves.

This study was performed: (1) to assess whether cyclosporine affected the increase in submaxillary lymph node ornithine decarboxylase activity induced by complete Freund's adjuvant injection to rats bearing a regional parasympathetic decentralization; (2) to examine the effect of cyclosporine on cholinergic markers in submaxillary lymph nodes of rats injected with complete Freund's adjuvant or its vehicle. The unilateral parasympathetic decentralization of the submaxillary lymph nodes was achieved by unilateral chorda tympani section; each rat was also contralaterally sham-operated. A 73% decrease of choline acetyltransferase activity and a 78% decrease of neuronal [3H]choline uptake, were found in the ipsilateral side 2 weeks after surgery. Cyclosporine (5 or 20 mg/kg) or its vehicle was s.c. injected once daily for 5 days. Freund's complete adjuvant or its vehicle was injected s.c. 1 h before the 3rd injection of cyclosporine. The animals were killed 2 h after the last cyclosporine injection. Parasympathetic decentralization of the submaxillary lymph nodes was followed, 2 weeks later, by a significant inhibition of cyclosporine activity on Freund's adjuvant-induced ornithine decarboxylase. In rats injected with complete Freund's adjuvant or its vehicle, sympathetic denervation of submaxillary lymph nodes achieved by unilateral superior cervical ganglionectomy, augmented the stimulatory activity of cyclosporine on choline acetyltransferase and neuronal choline uptake. Cyclosporine treatment did not modify the total [3H]choline uptake, regardless of Freund's adjuvant injection or of intactness of the sympathetic innervation. Choline acetyltransferase and choline uptake were significantly augmented by the injection of Freund's adjuvant alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in serum growth hormone and prolactin levels, and in hypothalamic growth hormone-releasing hormone, thyrotropin-releasing hormone and somatostatin content, after superior cervical sympathectomy in rats.

After bilateral superior cervical ganglionectomy (SCGx) of adult male rats, norepinephrine (NE) content of the medial basal hypothalamus (MBH) decreased significantly by 39-47% from 16 h to 7 days after surgery. During this time the levels of serum growth hormone (GH) and prolactin (PRL) and of MBH GH-releasing hormone (GRH), thyrotropin-releasing hormone (TRH) and somatostatin were measured by RIA. In sham-operated controls, serum PRL increased and serum GH decreased 16-24 h after surgery, attaining pre-surgical levels later on. In SCGx rats, significantly lower serum GH and PRL and higher MBH GRH and TRH content as compared to controls was observed 16-24 h after surgery, during the wallerian degeneration phase after SCGx. MBH somatostatin concentration decreased in SCGx rats 20 h after surgery. Two injections of the alpha 1-adrenoceptor blocker prazosin 45 and 90 min before sacrifice, alone or together with the beta-blocker propranolol, prevented the changes in MBH hypophysiotropic hormone content, as well as in serum GH and PRL levels, found in SCGx rats 20 h after surgery. Propranolol treatment did not affect hormone levels. Neither drug modified the decrease in MBH NE content observed after SCGx. The results argue in favor of the existence of physiologically relevant projections from superior cervical ganglion neurons to the MBH controlling hypophysiotropic hormone release.

Time-dependency for the bimodal effect of melatonin on calcium uptake in rat hypothalamus. Short communication.

The activity of 0.01-1 microM of melatonin on depolarization-induced 45Ca2+ influx by hypothalamic synaptosomes of rats killed at late evening (2000 h) depended on melatonin preincubation time, exhibiting an early (10 min) stimulation of uptake and an inhibition after 30 min of incubation. Both stimulatory and inhibitory effects were maximal at 2000 h and tended to a minimum at 2400 h, exhibiting intermediate values at 400 h. At 1000 h, only inhibitory effects of melatonin (1 microM) on Ca2+ uptake were found.