RESUMO
INTRODUCTION: Polyomavirus BK nephropathy is emerging as a significant cause of interstitial nephritis and allograft dysfunction (1-2). CASE REPORT: Two patients with renal transplants from cadaveric kidneys were treated with Tacrolimus plus Mycophenolate Mofetil (MMF) and Cyclosporine plus MMF, respectively. Their renal function gradually deteriorated eight to twelve months after the transplant. The renal biopsy of the first patient showed signs of significant interstitial tubulite, which necessitated the anti-rejection therapy with intravenous steroid pulses. After the pulses there was an additional dramatic increase in plasmatic creatinine, which suggested a revaluation of the kidney biopsy because of suspected Polyomavirus BK (BKV) nephropathy. In fact, after a more careful review, the suspicion of BKV infection was confirmed by the presence of intranuclear inclusions of tubular epithelium cells and marked denudation of the tubular basal membrane. The subsequent screening in both cases confirmed the presence of decoy cells in the urine, while the immunohistochemical analysis of the renal biopsy was strongly positive for the SV40 antigen. Our diagnosis was that of interstitial nephritis due to Polyomavirus BK that, in the first patient, was expressed by more aggressive clinical progress, probably due to enhanced immunosuppression from incorrect diagnosis of the interstitial rejection. The pre-transplant clinical outcome of the first patient was characterised by proteinuric nephropathy without any histological confirmation. Furthermore, we observed abundant pre-transplant residual diuresis and glucose intolerance. All these elements led us to hypothesise that native kidneys could have a fundamental role as viral reservoirs. CONCLUSION: Even though we reconfirm the decisive role of the immunosuppressive therapy and of the donor s kidney as the fundamental causes of Polyomavirus reactivation, we believe that it cannot be the result of a possible active role by the native kidney. In fact, as already noted, the SV40 genome is important in the pathogenesis of focal gomerulosclerosis. Furthermore, reports of polyoma nephropathy in not-yet-transplanted patients could accredit the role of the native kidneys as important viral reservoirs capable of inducing nephropathy in renal transplant patients.
Assuntos
Vírus BK , Neoplasias Renais/etiologia , Transplante de Rim/efeitos adversos , Infecções por Polyomavirus/etiologia , Infecções Tumorais por Vírus/etiologia , Adulto , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Monocyte/macrophages (M/M) represent the main cellular component of the immune system involved in the inflammatory response. In the present study we investigate whether NGF is produced by M/M and is involved in this event. The results show that unstimulated human M/M produce NGF and its synthesis is stimulated by LPS. The increase of NGF is associated with enhanced expression of high affinity NGF receptor on M/M and with no changes of low affinity NGF receptors (p75). The neutralization of endogenous NGF by NGF antibody in LPS-activated M/M, leads to overexpression of p75 receptor causing apoptosis. These findings provide new insight in the mechanisms governing monocyte survival in the inflamed tissue, representing a crucial aspect of host defence and maintenance of homeostasis.
Assuntos
Lipopolissacarídeos/farmacologia , Macrófagos/fisiologia , Monócitos/fisiologia , Fator de Crescimento Neural/metabolismo , Receptores de Fator de Crescimento Neural/metabolismo , Adulto , Anticorpos/farmacologia , Apoptose , Células Cultivadas , Humanos , Macrófagos/efeitos dos fármacos , Monócitos/efeitos dos fármacos , Fator de Crescimento Neural/imunologia , Receptor de Fator de Crescimento NeuralRESUMO
Infection of macrophages (M/M) by human immunodeficiency virus (HIV) is a main pathogenetic event leading to neuronal dysfunction and death in patients with AIDS dementia complex. Alteration of viability of neurons and astrocytes occurs in vivo even without their infection, thus it is conceivable that HIV-infected M/M may affect viability of such cells even without direct infection. To assess this hypothesis, we studied the effects of HIV-infected M/M on an astrocytic cell-line lacking CD4-receptor expression. Exposure to supernatants of HIV-infected M/M triggers complete disruption and apoptotic death of astrocytic cells. This effect is not related to HIV transmission from infected M/M, because HIV-DNA and p24 production in astrocytic cells remained negative. Apoptotic death of astrocytes is mainly mediated by Fas ligand released in supernatants of HIV-infected M/M (as demonstrated by complete reversal of such phenomenon by adding neutralizing antibodies against CD95 receptor). Treatment of astrocytic cells with recombinant (biologically active) Tat induces < 10% apoptosis, and gp120 was totally ineffective. Treatment of HIV-infected M/M with AZT completely reverses the proapoptotic effect of their supernatants on astrocytes, thus demonstrating that productive virus replication within M/M is required for the induction of astrocytic cell death. Taken together, data suggest that homeostasis of astrocytes may be affected by HIV-infected M/M in the absence of productive infection of target cells. This phenomenon may help to explain the cellular damage found in HIV-infected patients also in areas of the brain not strictly adjacent to HIV-infected M/M.
Assuntos
Apoptose/fisiologia , Astrócitos/patologia , Comunicação Celular/fisiologia , HIV , Macrófagos/virologia , Receptor fas/fisiologia , Fármacos Anti-HIV/farmacologia , Apoptose/efeitos dos fármacos , Células Cultivadas , Proteína Ligante Fas , Produtos do Gene tat/fisiologia , Proteína gp120 do Envelope de HIV/fisiologia , Homeostase , Humanos , Macrófagos/patologia , Masculino , Glicoproteínas de Membrana/fisiologia , Pessoa de Meia-Idade , Necrose , Zidovudina/farmacologia , Produtos do Gene tat do Vírus da Imunodeficiência HumanaRESUMO
Nerve growth factor (NGF) is a neurotrophin with the ability to exert specific effects on cells of the immune system. Human monocytes/macrophages (M/M) infected in vitro with HIV type 1 (HIV-1) are able to produce substantial levels of NGF that are associated with enhanced expression of the high-affinity NGF receptor (p140 trkA) on the M/M surface. Treatment of HIV-infected human M/M with anti-NGF Ab blocking the biological activity of NGF leads to a marked decrease of the expression of p140 trkA high-affinity receptor, a concomitant increased expression of p75(NTR) low-affinity receptor for NGF, and the occurrence of apoptotic death of M/M. Taken together, these findings suggest a role for NGF as an autocrine survival factor that rescues human M/M from the cytopathic effect caused by HIV infection.
Assuntos
HIV-1/fisiologia , Macrófagos/virologia , Fator de Crescimento Neural/fisiologia , Animais , Apoptose , Sobrevivência Celular , Células Cultivadas , Humanos , Macrófagos/citologia , Macrófagos/fisiologia , Coelhos , Receptor de Fator de Crescimento Neural/biossíntese , Receptor trkA/biossínteseRESUMO
The immunomodulatory effects of local administration of cocaine into the amygdala were studied in the rat. Intra-amygdala infusion of cocaine significantly and dose-dependently increased the proliferative response of splenocytes to concanavalin A (Con A). A similar effect on the immune response was also observed in rats, microinfused into the central amygdala with the selective D1 receptor agonist SKF 38393. The increase of the proliferative response of splenocytes to Con A was inhibited by coinfusion within the central amygdala of the dopamine D1 receptor antagonist SCH 23390, together with cocaine, but not by coinfusion of the dopamine D2 receptor antagonist eticlopride. These results suggest that cocaine may produce at least some of its effects on the immune system through the activation of brain dopamine neurotransmission and that the central amygdala may represent a critical structure mediating cocaine-induced T cell proliferation.
Assuntos
Tonsila do Cerebelo/metabolismo , Cocaína/farmacologia , Receptores de Dopamina D1/fisiologia , Baço/citologia , 2,3,4,5-Tetra-Hidro-7,8-Di-Hidroxi-1-Fenil-1H-3-Benzazepina/farmacologia , Animais , Benzazepinas/farmacologia , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Concanavalina A/farmacologia , Agonistas de Dopamina/farmacologia , Antagonistas de Dopamina/farmacologia , Relação Dose-Resposta a Droga , Masculino , Ratos , Ratos Wistar , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/antagonistas & inibidores , Salicilamidas/farmacologia , Baço/efeitos dos fármacosRESUMO
Indirect evidence suggests that dopamine within the brain may participate in the regulation of immune responses in both man and rodents. The aim of the present study was to investigate the possible role played by the specific dopamine D1 receptor subtype within the central amygdala in the modulation of immunity. Mitogen responsiveness of splenocytes and NK cell activity were measured in rats following local microinfusion of SKF 38393, a specific dopamine D1 receptor agonist. Microinfusion of SKF 38393 (100 nmol) within the central amygdala increased the proliferative response of splenocytes to Con A, whereas it did not modify the proliferative response of splenocytes to LPS or NK cell activity. The effects of SKF 38393 were prevented by prior systemic administration of SCH 23390 (0.3 mg/kg ip), a specific D1 receptor antagonist. These results indicate that activation of dopamine D1 receptors within the central amygdala induced selective stimulation of mitogen responsiveness of splenocytes and suggest that specific activation of dopamine neurotransmission within selected areas of the limbic system may produce immunoenhancing effects. These findings further confirm the immunomodulatory role played by dopaminergic mechanisms in the brain.
Assuntos
Tonsila do Cerebelo/fisiologia , Imunidade , Receptores de Dopamina D1/fisiologia , 2,3,4,5-Tetra-Hidro-7,8-Di-Hidroxi-1-Fenil-1H-3-Benzazepina/farmacologia , Tonsila do Cerebelo/efeitos dos fármacos , Animais , Benzazepinas/farmacologia , Divisão Celular/efeitos dos fármacos , Concanavalina A/farmacologia , Masculino , Ratos , Ratos Wistar , Baço/citologiaRESUMO
We have investigated the graft versus host (GvH) disease induced in immunodeficient SCID (H-2d) mice by intravenous (iv) or intraperitoneal (ip) transfer of either spleen or lymph node cells from autoimmune (MRL/lpr and MRL/++ mice, H-2k) and normal (CBA, H-2k) mice. Rapid and lethal GvH disease was observed when cells from MRL/lpr or MRL/++ were iv transferred into SCID mice, while spleen cells from nonautoimmune CBA donors were partially tolerized into SCID recipients and induced only lower levels of GvH reaction. No GvH reaction (complete tolerance) was observed when CBA lymph node cells were iv transferred into SCID recipients. In contrast, the ip injection of MRL/lpr or CBA spleen cells induces similar levels of GvH. The development of GvH disease in SCID recipients was due to the expansion of alloreactive CD8+ cells displaying significant cytotoxic activity against H-2d, but not against autologous targets. Also, a significant decrease of CD4/CD8 ratio was observed in the course of GvH caused by the iv transfer of cells from MRL/lpr mice. Altogether, these data support the hypothesis that lymphocytes from the MRL/lpr mice may escape tolerance in the GvH reaction.
Assuntos
Doença Enxerto-Hospedeiro/etiologia , Imunoterapia Adotiva , Animais , Relação CD4-CD8 , Transplante de Células/fisiologia , Citotoxicidade Imunológica , Reação Enxerto-Hospedeiro/imunologia , Tolerância Imunológica , Linfonodos/citologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Mutantes/genética , Camundongos SCID , Fenótipo , Baço/citologia , Baço/imunologiaRESUMO
Melatonin, the main hormone of the pineal gland, when chronically injected into young mice or mice immunodepressed by aging or by cyclophosphamide treatment, was able to enhance the antibody response to a T-dependent antigen. The enhancement of antibody response was associated with increased induction of T helper cell activity and IL-2 production as evidenced in mice immunodepressed by aging or by cyclophosphamide treatment. These observations suggest that melatonin may be successfully used in the therapy of immunodepressive conditions.
Assuntos
Adjuvantes Imunológicos/fisiologia , Formação de Anticorpos , Ciclofosfamida/uso terapêutico , Melatonina/fisiologia , Envelhecimento/imunologia , Animais , Formação de Anticorpos/imunologia , Linhagem Celular , Células Cultivadas , Eritrócitos/imunologia , Terapia de Imunossupressão , Interleucina-2/biossíntese , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Glândula Pineal/fisiologia , Linfócitos T Auxiliares-Indutores/imunologiaRESUMO
Indirect evidence suggests that dopamine within the brain may participate in the regulation of immune responses both in humans and in rodents. The aim of the present study was to investigate the possible modulatory role played by specific dopamine D1 receptor subtypes within discrete sites of the brain dopaminergic pathways. Mitogen responsiveness of splenocytes and natural killer (NK) cell activity were measured in rats following microinfusion of SKF 38393, a specific dopamine D1 receptor agonist, into the ventral tegmental area, the amygdala, the nucleus accumbens and the CA1 area of the hippocampus. We report here that microinfusion of SKF 38393 (100 nmol) within the central amygdala increased the proliferative response of splenocytes to concanavalin A (ConA) while it did not modify the proliferative response of splenocytes to lipopolysaccharide (LPS) or NK cell activity. On the contrary, microinfusion of SKF 38393 into the nucleus accumbens decreased the proliferative response of splenocytes to ConA and LPS, while NK cell activity remained unchanged. Similarly, microinfusion of SKF 38393 into the CA1 area of the hippocampus decreased the proliferative response of splenocytes to LPS, but not to ConA and did not affect NK cell activity. Finally, microinfusion of SKF 38393 into the ventral tegmental area did not significantly modify the proliferative response of splenocytes to either ConA or LPS and did not affect NK cell activity. All immunological changes evoked through the different areas of the brain following microinfusion of SKF 38393 were prevented by systemic administration of SCH 23390, a specific D1 receptor antagonist.
Assuntos
Antagonistas de Dopamina/farmacologia , Dopamina/fisiologia , Sistema Límbico/fisiologia , Neuroimunomodulação/fisiologia , Receptores de Dopamina D1/fisiologia , 2,3,4,5-Tetra-Hidro-7,8-Di-Hidroxi-1-Fenil-1H-3-Benzazepina/farmacologia , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/fisiologia , Animais , Benzazepinas/farmacologia , Concanavalina A/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Sistema Límbico/efeitos dos fármacos , Lipopolissacarídeos/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Masculino , Mitógenos/farmacologia , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/fisiologia , Ratos , Ratos WistarRESUMO
In freely moving rats with cannulae chronically implanted into the locus coeruleus (LC), the effects of corticotropin-releasing factor (CRF) on electrocortical (ECoG) spectrum power activity and on immune mechanisms (splenocyte mitotic response to concanavalin A, Con A, and lipopolysaccharide, LPS, natural killer cell, NK, activity) were assessed. CRF (100-300 ng) microinfused into the LC produced marked ECoG desynchronization characterized by a significant decrease in total voltage power as well as in power of frequency bands of 0.25-3 and 3-6 Hz. These effects lasted 30-60 min according to the dose. A prior administration of alpha-helical CRF(9-41) (200 ng into the LC 15 min before) prevented ECoG desynchronization induced by CRF (100 ng). In addition, CRF (100 ng) given into the LC produced a significant decrease 45 min later in the splenocyte proliferative response to Con A and LPS and a significant fall of NK activity. These effects were prevented by prior microinfusion into the same site of alpha-helical CRF (200 ng). In conclusion, the present experiments show that CRF given into the LC produces an intense state of ECoG desynchronization accompanied by marked immunodepression and suggest that LC is an important site in the brain through which CRF exerts its immunosuppressive activity.
Assuntos
Hormônio Liberador da Corticotropina/toxicidade , Eletrocardiografia/efeitos dos fármacos , Terapia de Imunossupressão , Locus Cerúleo/efeitos dos fármacos , Neuroimunomodulação/fisiologia , Animais , Hormônio Liberador da Corticotropina/administração & dosagem , Hormônio Liberador da Corticotropina/antagonistas & inibidores , Hormônio Liberador da Corticotropina/farmacologia , Antagonistas de Hormônios/farmacologia , Imunidade Celular/efeitos dos fármacos , Infusões Parenterais , Células Matadoras Naturais/imunologia , Locus Cerúleo/fisiologia , Ativação Linfocitária/efeitos dos fármacos , Mitógenos/farmacologia , Fragmentos de Peptídeos/farmacologia , RatosRESUMO
Opioid peptides have been shown by several studies to modulate various parameters of the immune response, but scant experimental findings exist on the role played by specific opioid receptor subtypes in the control of immune mechanisms. This study focuses on the in vitro influences of [Trp4,Asn7]dermorphin, a mu-selective agonist, [D-Ala2]deltorphin I, a delta-selective agonist and U50,488, a kappa-selective agonist, on the proliferative response of splenocytes to concanavalin A (Con A). [Trp4,Asn7]dermorphin at low concentrations (10(-11P) and 10(-12) M) enhanced the proliferative response to Con A, whereas higher concentrations (10(-6) to 10(-7) M) inhibited it. Both effects were antagonized by naloxone. [D-Ala2]deltorphin I at very low concentrations (10(-12) to 10(-13) M) also produced a significant increase in the proliferative response of splenocytes to Con A. This effect was significantly antagonized by natrindole, a specific delta-receptor antagonist. Finally U50,488 at concentrations ranging from 10(-8) to 10(-9) M inhibited the proliferative response to Con A. The effects of U50,488 were mediated by the stimulation of the kappa-opioid receptors, since a preincubation of splenocytes with the selective antagonist norbinaltorphimine significantly reduced or abolished the U50,488-induced suppression of the mitotic response. In conclusion, our results clearly indicate that the different opioid receptor subtypes play a different role in the control of immune mechanisms and suggest that immunoenhancing effects of opioid peptides are very likely due to the stimulation of mu- and delta-receptors, whereas the immunosuppressive effects are mediated through the stimulation of kappa-opioid receptors.
Assuntos
Imunidade Celular/fisiologia , Ativação Linfocitária/efeitos dos fármacos , Naltrexona/análogos & derivados , Antagonistas de Entorpecentes/farmacologia , Oligopeptídeos/farmacologia , Pirrolidinas/farmacologia , Receptores Opioides/fisiologia , (trans)-Isômero de 3,4-dicloro-N-metil-N-(2-(1-pirrolidinil)-ciclo-hexil)-benzenoacetamida , Sequência de Aminoácidos , Animais , Concanavalina A/farmacologia , Imunidade Celular/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Naloxona/farmacologia , Naltrexona/farmacologia , Receptores Opioides/agonistas , Receptores Opioides/classificação , Receptores Opioides/efeitos dos fármacosRESUMO
Rat/human-corticotropin-releasing hormone (CRH) microinfused unilaterally into the locus coeruleus (LC) of awake, chronically cannulated rats produced intense behavioral stimulation accompanied by a marked decrease of the proliferative response of splenocytes to Con A and LPS and natural killer activity. These effects were specifically prevented by prior administration into the same site of the CRH antagonist (alpha-helical CRH [9-41]). The present results confirm that a strict relationship exists between the CNS and cell-mediated immunity; in addition, they also indicate that CRH produces its behavioral and immune changes by an interaction with specific receptors and that one of the main sites through which CRH exerts these effects is represented by the LC.
Assuntos
Hormônio Liberador da Corticotropina/farmacologia , Imunidade Celular/efeitos dos fármacos , Locus Cerúleo/efeitos dos fármacos , Ratos Wistar , Animais , Comportamento Animal/efeitos dos fármacos , Células Matadoras Naturais/efeitos dos fármacos , Locomoção/efeitos dos fármacos , Masculino , Vias Neurais/efeitos dos fármacos , Ratos , Baço/efeitos dos fármacosRESUMO
Our preceding results have shown that melatonin administration to normal and immunodepressed mice increases significantly the antibody response. We also found that melatonin is able to restore the impaired T-helper cell activity in immunodepressed mice. The present study shows that melatonin enhances antigen presentation by splenic macrophages to T-cells. This effect is concomitant with an increase in the expression of MHC class II molecules and production of IL-1 and TNF-alpha. Considering the role of antigen presentation and cytokine production in the initiation of the immune response, the present findings provide evidence for relevant mechanisms that may account for the regulatory role of the pineal gland in immunoregulation.
Assuntos
Células Apresentadoras de Antígenos/efeitos dos fármacos , Melatonina/farmacologia , Linfócitos T/efeitos dos fármacos , Animais , Células Apresentadoras de Antígenos/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Interleucina-1/biossíntese , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Glândula Pineal/imunologia , Linfócitos T/imunologia , Fator de Necrose Tumoral alfa/biossínteseRESUMO
The passive transfer of contact sensitivity using picryl chloride immune cells from H-2 syngenic BALB/c donors was analyzed in severe combined immunodeficiency (SCID) mice which lack functional T and B lymphocytes. H-2-restricted and antigen-specific contact sensitivity was transferred to SCID mice, and comparison between the level of contact sensitivity and the number of transferred cells showed a significantly more efficient transfer to SCID than to BALB/c mice. The cells passively transferring contact sensitivity were shown to carry the V beta 8 phenotype. Moreover, chromium-labeled cells from BALB/c PC1-primed donors localize normally in peripheral lymphoid organs and an increased percentage of cell arrival in the ears is clearly observed in SCID after challenge with picryl chloride.
Assuntos
Camundongos SCID/imunologia , Cloreto de Picrila/efeitos adversos , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Animais , Dermatite de Contato/etiologia , Dermatite de Contato/imunologia , Orelha/anatomia & histologia , Feminino , Imunização Passiva , Região Variável de Imunoglobulina/genética , Linfonodos/citologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C/imunologia , Fenótipo , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Linfócitos T/citologia , Distribuição TecidualAssuntos
Sistema Imunitário/efeitos dos fármacos , Melatonina/farmacologia , Animais , Concanavalina A/farmacologia , Ciclofosfamida/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Baço/citologia , Baço/efeitos dos fármacos , Linfócitos T Auxiliares-Indutores/efeitos dos fármacos , Linfócitos T Auxiliares-Indutores/imunologiaRESUMO
Melatonin, the main hormone of the pineal gland, when chronically injected into young mice or mice immunodepressed by aging or by cyclophosphamide treatment, is able to enhance the antibody response to a T-dependent antigen. The enhancement of the antibody response is associated with increased induction of T helper cell activity and IL-2 production, as evidenced in mice immunodepressed by aging or by cyclophosphamide treatment. These observations suggest that melatonin treatment may be successfully used in the therapy of immunodepressive conditions.
Assuntos
Adjuvantes Imunológicos/farmacologia , Síndromes de Imunodeficiência/tratamento farmacológico , Melatonina/farmacologia , Envelhecimento/imunologia , Animais , Formação de Anticorpos/efeitos dos fármacos , Ciclofosfamida , Síndromes de Imunodeficiência/etiologia , Síndromes de Imunodeficiência/imunologia , Técnicas In Vitro , Interleucina-2/biossíntese , Masculino , Melatonina/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Linfócitos T Auxiliares-Indutores/efeitos dos fármacos , Linfócitos T Auxiliares-Indutores/imunologiaAssuntos
Melatonina/farmacologia , Linfócitos T Auxiliares-Indutores/efeitos dos fármacos , Animais , Ciclofosfamida/farmacologia , Eritrócitos/imunologia , Cavalos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Linfócitos T Auxiliares-Indutores/imunologiaRESUMO
The involvement of the cholinergic system in GH secretion has recently acquired increasing importance. Data have been presented suggesting that in rats the effect of cholinergic modulation on GH secretion takes place through inhibition or stimulation of hypothalamic somatostatin (SRIF) release. To investigate further the significance of cholinergic-SRIF link and its role in the regulation of GH secretion, the action of cholinergic agonist and antagonist drugs in the GH short-loop feedback mechanism mediated by SRIF was investigated. Intracerebroventricular (i.c.v.) infusion of 0.2 or 2.0 micrograms GH/rat into the lateral brain ventricle of adult male rats induced a significant reduction in the GH-releasing hormone (GHRH; 2 micrograms/kg, i.v.)-induced peak GH rise, but only the 2.0 micrograms dose reduced also the GH-integrated area after administration of GHRH. This effect was absent after central administration of 20.0 micrograms GH/rat, due probably to leakage of some GH from the cerebral ventricle into the systemic circulation. Pretreatment with cysteamine (300 mg/kg, s.c.), a known depletor of hypothalamic SRIF, or with anti-SRIF serum (0.5 ml/rat) completely counteracted the lessening of the GH response to GHRH induced by 2.0 micrograms GH injected i.c.v. Similarly, pretreatment with the cholinergic agonist pilocarpine (3 mg/kg, i.v.) completely antagonized the inhibitory effect of central infusion of GH on the GHRH-induced GH response. Atropine (1.0 mg/kg, i.v.), a muscarinic cholinergic antagonist, strikingly inhibited the GHRH-induced GH rise, but when given in combination with i.c.v. infusion of GH there was no additive inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)