Phosphatase 1 Nuclear Targeting Subunit Mediates Recruitment and Function of Poly (ADP-Ribose) Polymerase 1 in DNA Repair

PARP, particularly PARP1, plays an essential role in the detection and repair of DNA single-strand breaks and double-strand breaks. PARP1 accumulates at DNA damage sites within seconds after DNA damage to catalyze the massive induction of substrate protein poly ADP-ribosylation (PARylation). However, the molecular mechanisms underlying the recruitment and activation of PARP1 in DNA repair are not fully understood. Here we show that phosphatase 1 nuclear targeting subunit 1 (PNUTS) is a robust binding partner of PARP1. Inhibition of PNUTS led to strong accumulation of endogenous DNA damage and sensitized the cellular response to a wide range of DNA-damaging agents, implicating PNUTS as an essential and multifaceted regulator of DNA repair. Recruitment of PNUTS to laser-induced DNA damage was similar to that of PARP1, and depletion or inhibition of PARP1 abrogated recruitment of PNUTS to sites of DNA damage. Conversely, PNUTS was required for efficient induction of substrate PARylation after DNA damage. PNUTS bound the BRCA1 C-terminal (BRCT) domain of PARP1 and was required for the recruitment of PARP1 to sites of DNA damage. Finally, depletion of PNUTS rendered cancer cells hypersensitive to PARP inhibition. Taken together, our study characterizes PNUTS as an essential partner of PARP1 in DNA repair and a potential drug target in cancer therapy. SIGNIFICANCE: These findings reveal PNUTS as an essential functional partner of PARP1 in DNA repair and suggest its inhibition as a potential therapeutic strategy in conjunction with DNA-damaging agents or PARP inhibitors.See related commentary by Murai and Pommier, p. 2460.

Phosphatase 1 Nuclear Targeting Subunit (PNUTS) Regulates Aurora Kinases and Mitotic Progression

Mitotic progression is regulated largely by reversible phosphorylation events that are mediated by mitotic kinases and phosphatases. Protein phosphatase 1 (PP1) has been shown to play a crucial role in regulation of mitotic entry, progression, and exit. We previously observed, in Xenopus egg extracts, that phosphatase 1 nuclear targeting subunit (PPP1R10/PNUTS) acts as a mitotic regulator by negatively modulating PP1. This study investigates the role of PNUTS in mitotic progression in mammalian cells, and demonstrates that PNUTS expression is elevated in mitosis and depletion partially blocks mitotic entry. Cells that enter mitosis after PNUTS knockdown exhibit frequent chromosome mis-segregation. Aurora A/B kinase complexes and several kinetochore components are identified as PNUTS-associated proteins. PNUTS depletion suppresses the activation of Aurora A/B kinases, and disrupts the spatiotemporal regulation of the chromosomal passenger complex (CPC). PNUTS dynamically localizes to kinetochores, and is required for the activation of the spindle assembly checkpoint. Finally, PNUTS depletion sensitizes the tumor cell response to Aurora inhibition, suggesting that PNUTS is a potential drug target in combination anticancer therapy. IMPLICATIONS: Delineation of how PNUTS governs the mitotic activation and function of Aurora kinases will improve the understanding of the complex phospho-regulation in mitotic progression, and suggest new options to enhance the therapeutic efficacy of Aurora inhibitors.

Protein phosphatase 1 and phosphatase 1 nuclear targeting subunit-dependent regulation of DNA-dependent protein kinase and non-homologous end joining

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) plays a key role in mediating non-homologous end joining (NHEJ), a major repair pathway for DNA double-strand breaks (DSBs). The activation, function and dynamics of DNA-PKcs is regulated largely by its reversible phosphorylation at numerous residues, many of which are targeted by DNA-PKcs itself. Interestingly, these DNA-PKcs phosphorylation sites function in a distinct, and sometimes opposing manner, suggesting that they are differentially regulated via complex actions of both kinases and phosphatases. In this study we identified several phosphatase subunits as potential DSB-associated proteins. In particular, protein phosphatase 1 (PP1) is recruited to a DSB-mimicking substrate in Xenopus egg extracts and sites of laser microirradiation in human cells. Depletion of PP1 impairs NHEJ in both Xenopus egg extracts and human cells. PP1 binds multiple motifs of DNA-PKcs, regulates DNA-PKcs phosphorylation, and is required for DNA-PKcs activation after DNA damage. Interestingly, phosphatase 1 nuclear targeting subunit (PNUTS), an inhibitory regulator of PP1, is also recruited to DNA damage sites to promote NHEJ. PNUTS associates with the DNA-PK complex and is required for DNA-PKcs phosphorylation at Ser-2056 and Thr-2609. Thus, PNUTS and PP1 together fine-tune the dynamic phosphorylation of DNA-PKcs after DNA damage to mediate NHEJ.

Cell cycle-dependent regulation of Greatwall kinase by protein phosphatase 1 and regulatory subunit 3B

Greatwall (Gwl) kinase plays an essential role in the regulation of mitotic entry and progression. Mitotic activation of Gwl requires both cyclin-dependent kinase 1 (CDK1)-dependent phosphorylation and its autophosphorylation at an evolutionarily conserved serine residue near the carboxyl terminus (Ser-883 in Xenopus). In this study we show that Gwl associates with protein phosphatase 1 (PP1), particularly PP1γ, which mediates the dephosphorylation of Gwl Ser-883. Consistent with the mitotic activation of Gwl, its association with PP1 is disrupted in mitotic cells and egg extracts. During mitotic exit, PP1-dependent dephosphorylation of Gwl Ser-883 occurs prior to dephosphorylation of other mitotic substrates; replacing endogenous Gwl with a phosphomimetic S883E mutant blocks mitotic exit. Moreover, we identified PP1 regulatory subunit 3B (PPP1R3B) as a targeting subunit that can direct PP1 activity toward Gwl. PPP1R3B bridges PP1 and Gwl association and promotes Gwl Ser-883 dephosphorylation. Consistent with the cell cycle-dependent association of Gwl and PP1, Gwl and PPP1R3B dissociate in M phase. Interestingly, up-regulation of PPP1R3B facilitates mitotic exit and blocks mitotic entry. Thus, our study suggests PPP1R3B as a new cell cycle regulator that functions by governing Gwl dephosphorylation.

Regulation of Greatwall kinase by protein stabilization and nuclear localization

Greatwall (Gwl) functions as an essential mitotic kinase by antagonizing protein phosphatase 2A. In this study we identified Hsp90, Cdc37 and members of the importin α and β families as the major binding partners of Gwl. Both Hsp90/Cdc37 chaperone and importin complexes associated with the N-terminal kinase domain of Gwl, whereas an intact glycine-rich loop at the N-terminus of Gwl was essential for binding of Hsp90/Cdc37 but not importins. We found that Hsp90 inhibition led to destabilization of Gwl, a mechanism that may partially contribute to the emerging role of Hsp90 in cell cycle progression and the anti-proliferative potential of Hsp90 inhibition. Moreover, in agreement with its importin association, Gwl exhibited nuclear localization in interphase Xenopus S3 cells, and dynamic nucleocytoplasmic distribution during mitosis. We identified KR456/457 as the locus of importin binding and the functional NLS of Gwl. Mutation of this site resulted in exclusion of Gwl from the nucleus. Finally, we showed that the Gwl nuclear localization is indispensable for the biochemical function of Gwl in promoting mitotic entry.

Regulation of polo-like kinase 1 by DNA damage and PP2A/B55α

In addition to governing mitotic progression, Plk1 also suppresses the activation of the G2 DNA damage checkpoint and promotes checkpoint recovery. Previous studies have shown that checkpoint activation after DNA damage requires inhibition of Plk1, but the underlying mechanism of Plk1 regulation was unknown. In this study we show that the specific phosphatase activity toward Plk1 Thr-210 in interphase Xenopus egg extracts is predominantly PP2A-dependent, and this phosphatase activity is upregulated by DNA damage. Consistently, PP2A associates with Plk1 and the association increases after DNA damage. We further revealed that B55α, a targeting subunit of PP2A and putative tumor suppressor, mediates PP2A/Plk1 association and Plk1 dephosphorylation. B55α and PP2A association is greatly strengthened after DNA damage in an ATM/ATR and checkpoint kinase-dependent manner. Collectively, we report a phosphatase-dependent mechanism that responds to DNA damage and regulates Plk1 and checkpoint recovery.

Phosphatase 1 nuclear targeting subunit is an essential regulator of M-phase entry, maintenance, and exit

Mitotic progression is regulated largely through dynamic and reversible protein phosphorylation that is modulated by opposing actions of protein kinases and phosphatases. In this study, we show that phosphatase 1 nuclear targeting subunit (Pnuts) functions as a master regulator of mitosis by modulating protein phosphatase 1 (PP1). Overexpression of Pnuts in Xenopus egg extracts inhibited both mitotic and meiotic exit. Immunodepletion of Pnuts from egg extracts revealed its essential functions in mitotic entry and maintenance. The level of Pnuts oscillates during the cell cycle and peaks in mitosis. Pnuts destruction during M-phase exit is mediated by the anaphase-promoting complex/cyclosome (APC/C)-targeted ubiquitination and proteolysis, and conserved destruction motifs of Pnuts. Disruption of Pnuts degradation delayed M-phase exit, suggesting it as an important mechanism to permit M-phase exit.

Monoclonal antibodies against Xenopus greatwall kinase

Mitosis is known to be regulated by protein kinases, including MPF, Plk1, Aurora kinases, and so on, which become active in M-phase and phosphorylate a wide range of substrates to control multiple aspects of mitotic entry, progression, and exit. Mechanistic investigations of these kinases not only provide key insights into cell cycle regulation, but also hold great promise for cancer therapy. Recent studies, largely in Xenopus, characterized a new mitotic kinase named Greatwall (Gwl) that plays essential roles in both mitotic entry and maintenance. In this study, we generated a panel of mouse monoclonal antibodies (MAbs) specific for Xenopus Gwl and characterized these antibodies for their utility in immunoblotting, immunoprecipitation, and immunodepletion in Xenopus egg extracts. Importantly, we generated an MAb that is capable of neutralizing endogenous Gwl. The addition of this antibody into M-phase extracts results in loss of mitotic phosphorylation of Gwl, Plk1, and Cdk1 substrates. These results illustrate a new tool to study loss-of-function of Gwl, and support its essential role in mitosis. Finally, we demonstrated the usefulness of the MAb against human Gwl/MASTL.

Removal of reactive oxygen species-induced 3'-blocked ends by XPF-ERCC1

XPF-ERCC1 is a structure-specific endonuclease that is essential for nucleotide excision repair and DNA interstrand cross-link repair in mammalian cells. The yeast counterpart of XPF-ERCC1, Rad1-Rad10, plays multiple roles in DNA repair. Rad1-Rad10 is implicated to be involved in the repair of oxidative DNA damage. To explore the role(s) of XPF-ERCC1 in the repair of DNA damage induced by reactive oxygen species (ROS), cellular sensitivity of the XPF-deficient Chinese hamster ovary cell line UV41 to ROS was investigated. The XPF-deficient UV41 showed sensitivity to hydrogen peroxide, bleomycin, and paraquat. Furthermore, XPF-ERCC1 showed an ability to remove 3'-blocked ends such as 3'-phosphoglycolate from the 3'-end of DNA in vitro. These data suggest that XPF-ERCC1 plays a role in the repair of ROS-induced DNA damage by trimming 3'-blocked ends. The accumulation of various types of DNA damage, including ROS-induced DNA damage due to defects in multiple XPF-ERCC1-mediated DNA repair pathways, could contribute to the accelerated aging phenotypes observed in an XPF-ERCC1-deficient patient.

Role of interaction of XPF with RPA in nucleotide excision repair

Nucleotide excision repair (NER) is a very important defense system against various types of DNA damage, and it is necessary for maintaining genomic stability. The molecular mechanism of NER has been studied in considerable detail, and it has been shown that proper protein-protein interactions among NER factors are critical for efficient repair. A structure-specific endonuclease, XPF-ERCC1, which makes the 5' incision in NER, was shown to interact with a single-stranded DNA binding protein, RPA. However, the biological significance of this interaction was not studied in detail. We used the yeast two-hybrid assay to determine that XPF interacts with the p70 subunit of RPA. To further examine the role of this XPF-p70 interaction, we isolated a p70-interaction-deficient mutant form of XPF that contains a single amino acid substitution in the N-terminus of XPF by the reverse yeast two-hybrid assay using randomly mutagenized XPF. The biochemical properties of this RPA-interaction-deficient mutant XPF-ERCC1 are very similar to those of wild-type XPF-ERCC1 in vitro. Interestingly, expression of this mutated form of XPF in the XPF-deficient Chinese hamster ovary cell line, UV41, only partially restores NER activity and UV resistance in vivo compared to wild-type XPF. We discovered that the RPA-interaction-deficient XPF is not localized in nuclei and the mislocalization of XPF-ERCC1 prevents the complex from functioning in NER.

Greatwall and Polo-like kinase 1 coordinate to promote checkpoint recovery

Checkpoint recovery upon completion of DNA repair allows the cell to return to normal cell cycle progression and is thus a crucial process that determines cell fate after DNA damage. We previously studied this process in Xenopus egg extracts and established Greatwall (Gwl) as an important regulator. Here we show that preactivated Gwl kinase can promote checkpoint recovery independently of cyclin-dependent kinase 1 (Cdk1) or Plx1 (Xenopus polo-like kinase 1), whereas depletion of Gwl from extracts exhibits no synergy with that of Plx1 in delaying checkpoint recovery, suggesting a distinct but related relationship between Gwl and Plx1. In further revealing their functional relationship, we found mutual dependence for activation of Gwl and Plx1 during checkpoint recovery, as well as their direct association. We characterized the protein association in detail and recapitulated it in vitro with purified proteins, which suggests direct interaction. Interestingly, Gwl interaction with Plx1 and its phosphorylation by Plx1 both increase at the stage of checkpoint recovery. More importantly, Plx1-mediated phosphorylation renders Gwl more efficient in promoting checkpoint recovery, suggesting a functional involvement of such regulation in the recovery process. Finally, we report an indirect regulatory mechanism involving Aurora A that may account for Gwl-dependent regulation of Plx1 during checkpoint recovery. Our results thus reveal novel mechanisms underlying the involvement of Gwl in checkpoint recovery, in particular, its functional relationship with Plx1, a well characterized regulator of checkpoint recovery. Coordinated interplays between Plx1 and Gwl are required for reactivation of these kinases from the G(2)/M DNA damage checkpoint and efficient checkpoint recovery.

Processing of a psoralen DNA interstrand cross-link by XPF-ERCC1 complex in vitro

The processing of stalled forks caused by DNA interstrand cross-links (ICLs) has been proposed to be an important step in initiating mammalian ICL repair. To investigate a role of the XPF-ERCC1 complex in this process, we designed a model substrate DNA with a single psoralen ICL at a three-way junction (Y-shaped DNA), which mimics a stalled fork structure. We found that the XPF-ERCC1 complex makes an incision 5' to a psoralen lesion on Y-shaped DNA in a damage-dependent manner. Furthermore, the XPF-ERCC1 complex generates an ICL-specific incision on the 3'-side of an ICL. The ICL-specific 3'-incision, along with the 5'-incision, on the cross-linked Y-shaped DNA resulted in the separation of the two cross-linked strands (the unhooking of the ICL) and the induction of a double strand break near the cross-linked site. These results implicate the XPF-ERCC1 complex in initiating ICL repair by unhooking the ICL, which simultaneously induces a double strand break at a stalled fork.

Central actions of corticotropin-releasing factor on autonomic nervous activity and cardiovascular functioning

The physiological role of corticotropin-releasing factor (CRF) in mediating stress-induced activation of the pituitary-adrenal axis, together with the neuroanatomical distribution of immunoreactive CRF and CRF receptors, provides a compelling rationale for investigating actions of CRF within the central nervous system (CNS) on autonomic nervous outflow and cardiovascular function. Evidence is reviewed showing that CRF acts within the CNS to elicit stress-like patterns of autonomic nervous outflow and cardiovascular changes in conscious animals. In addition, blockade of CRF-mediated neurotransmission is demonstrated to alter the expression of stress-induced autonomic nervous and cardiovascular responses. Together, the anatomical, pharmacological and physiological data support the hypothesis that the autonomic nervous and cardiovascular responses to selected stressful stimuli may be mediated in part by CRF-containing neuronal pathways.

Opioid peptides and dipeptidyl peptidase in autism

It has been hypothesized that autism results from an 'opioid peptide excess'. The aims of this study were to (1) confirm the presence of opioid peptides in the urine of children with autism and (2) determine whether dipeptidyl peptidase IV (DPPIV/CD26) is defective in children with autism. Opioid peptides were not detected in either the urine of children with autism (10 children; nine males, one female; age range 2 years 6 months to 10 years 1 month) or their siblings (10 children; seven males, three females; age range 2 years 3 months to 12 years 7 months) using liquid chromatography-ultraviolet-mass spectrometric analysis (LC-UV-MS). Plasma from 11 normally developing adults (25 years 5 months to 55 years 5 months) was also tested. The amount and activity of DPPIV in the plasma were quantified by an ELISA and DPPIV enzyme assay respectively; DPPIV was not found to be defective. The percentage of mononuclear cells expressing DPPIV (as CD26) was determined by flow cytometry. Children with autism had a significantly lower percentage of cells expressing CD3 and CD26, suggesting that they had lower T-cell numbers than their siblings. In conclusion, this study failed to replicate the findings of others and questions the validity of the opioid peptide excess theory for the cause of autism.

Hemorrhagic complications of pancreatitis: radiologic evaluation with emphasis on CT imaging

OBJECTIVE

To analyze and describe the incidence, pathophysiology, radiographic diagnosis and the initial management of hemorrhagic complications associated with pancreatitis.

MATERIAL AND METHODS

Among 1,910 patients diagnosed of having pancreatitis in the last 10 years, 26 developed hemorrhagic complications (1.3%). These complications were detected from 2 months to 8 years after one or several episodes of pancreatitis with a mean of 2.3 years. Radiographic studies were reviewed and clinical management and outcome were recorded.

RESULTS

Ten patients had CT evidence of pancreatic necrosis, 12 patients chronic pancreatitis, and 17 patients pancreatic pseudocysts. The cause of hemorrhage was bleeding pseudoaneurysm in 16 patients (61%), diffuse bleeding with pancreatic necrosis in 5 patients (19.5%) and hemorrhagic pseudocysts in 5 patients (19.5%). Intra-abdominal hemorrhage developed in 21 patients and gastro-intestinal bleeding in 5 patients. Arterial embolization was attempted in 12 patients and was successful in 9 patients (75%). Surgery was used in 16 patients and the overall mortality rate was 11%.

CONCLUSIONS

Hemorrhagic complications are rarely seen and are usually late sequelae of pancreatitis. They develop because of leaking or ruptured pseudoaneurysms, diffuse bleeding in pancreatic necrosis, and hemorrhagic pseudocysts. Early detection followed by angiography, embolization and/or surgery has decreased mortality rates.

Translation and linguistic validation of a disease-specific quality of life measure for cystic fibrosis

OBJECTIVE

To develop a conceptually and semantically valid English version of a French disease-specific measure of quality of life for children, adolescents, and adults with cystic fibrosis (CF).

METHODS

Following a backward and forward translation of the measure, 60 participants, including 20 children, 20 parents, and 20 adolescents/young adults completed the Cystic Fibrosis Questionnaire (CFQ) and a series of cognitive probes evaluating their understanding of the items and response choices.

RESULTS

Semantic and conceptual problems with the items were identified and modified for the second set of cognitive interviews. Response distributions across items and ages were adequate, and the predicted associations between disease severity and quality of life were obtained.

CONCLUSIONS

The English version of the CFQ appears to be a linguistically valid measure of quality of life for patients with CF. A national validation study is now under way to test the psychometric properties of the measure.

Peer-Led Alcohol Education program: a pharmacy student-led program for seventh-graders

OBJECTIVE

To delay or discourage the use of alcohol by seventh-grade students through peer-led education. Peer-Led Alcohol Education (PLAE) program objectives were to: (1) educate students about alcohol use and (2) assess the differences between pharmacy student presenters and high school student (peer) presenters.

SETTING

Middle schools in rural Nebraska.

DESIGN

PLAE focuses on normative beliefs, personal values, and pledging. Pharmacy students and high school students were trained to deliver alcohol education presentations to seventh-grade students. Evaluation results were compared among groups of seventh-grade students who received PLAE presentations from peer presenters and from pharmacy student presenters.

RESULTS

PLAE presentations were made to 342 seventh-grade students at 11 schools. Evaluation results suggest that pharmacy students projected more confidence in their presentations, used more creative prop selections, and were more effective communicators. High-school presenters had a greater ability to "relate" to the seventh-graders and thus were deemed more on-target with the information.

CONCLUSION

Evaluation findings suggest that rural seventh-grade students in Nebraska perceived that the PLAE program provides useful information to aid them in their decisions regarding alcohol use.

Predicting relapse to substance abuse as a function of personality dimensions

The goal of the present study was to determine whether personality traits are related to return to heavy drinking or drug use following treatment for substance abuse. Personality characteristics of one hundred and eight patients residing on an inpatient substance abuse treatment program were assessed. Personality traits were examined using the 5-factor model of personality as measured by the NEO-Personality Inventory. These patients were then followed for 1 year after discharge from the treatment program. These substance abuse patients scored higher than the NEO-Personality Inventory normative sample on the personality domains of Neuroticism and Conscientiousness. A survival analysis showed that Neuroticism and Conscientiousness from the NEO-Personality Inventory were significant predictors of relapse. Odds ratios showed that the risk of relapsing was greatest for those patients who were both low in conscientiousness and high in neuroticism. The relevance of these two broad personality dimensions to the development and maintenance of addiction is discussed. Treatment implications for patients who possess these personality risk factors are outlined.

CNS actions of serotonin on cardiovascular function: nonadrenergic, noncholinergic mechanisms

The present studies investigated the mechanisms mediating the cardiovascular changes induced by intracerebroventricular injection of serotonin (5-HT; 100 nmol) in conscious rats. At 5 min after 5-HT injection, arterial pressure and plasma levels of epinephrine were elevated and heart rate was reduced. The pressor response was abolished either by bilateral adrenalectomy or by pretreatment with chlorisondamine plus vasopressin V1 receptor antagonist. The bradycardic response was attenuated by pretreatment with chlorisondamine or a combination of methylatropine, propranolol, and vasopressin V1 receptor antagonist. At 20 min postinjection, arterial pressure and heart rate were both decreased. The reduction of heart rate at this time point was not blocked by the following pretreatments given alone or in combination: methylatropine, propranolol, vasopressin V1 and V2 receptor antagonists, adenosine A1 receptor antagonist, angiotensin-converting enzyme inhibitor, and chlorisondamine. These results suggest that immediately after intracerebroventricular injection of 5-HT, arterial pressure is elevated through the release of epinephrine and vasopressin and that heart rate is reduced via reciprocal changes in cardiac parasympathetic and sympathetic tone. In contrast, adrenergic, cholinergic, vasopressinergic, purinergic, and angiotensinergic mechanisms do not mediate the bradycardia observed at 20 min postinjection.

Cardiovascular activation by serotonergic stimulation: role of corticotropin-releasing factor

Serotonin (5-HT) and serotonergic agonists stimulate the release of corticotropin-releasing factor (CRF) from hypophysiotropic neurons and thereby activate the pituitary-adrenal axis. Studies were performed to test the hypothesis that the release of CRF into central nervous system (CNS) sites where it influences cardiovascular function is likewise stimulated by serotonergic mechanisms. Experiments were thus designed to examine whether the cardiovascular effects of central administration of low doses of 5-HT and the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), are secondary to the release of CRF. Intracerebroventricular administration of 5-HT (1 nmol) and 8-OH-DPAT (3 nmol) produced cardiovascular responses similar to those evoked by CRF (0.15 nmol), i.e., simultaneous elevations of arterial pressure and heart rate, in conscious unrestrained rats. Coadministration of the CRF receptor antagonist, alpha-helical CRF-(9-41) (9 nmol), significantly attenuated the pressor and tachycardic responses to 5-HT and 8-OH-DPAT as well as those to injection of CRF. In contrast, coadministration of alpha-helical CRF-(9-41) did not alter the pressor and bradycardic responses to a high dose (100 nmol) of serotonin. It is concluded that the cardiovascular effects of low doses of 5-HT and 8-OH-DPAT are mediated in part through the release of CRF within the CNS.

Neuropeptides and the autonomic nervous system

Peptides are a class of intercellular messengers that are found in virtually every bodily organ. Evidence is reviewed here that peptides may function physiologically in brain pathways that coordinate and integrate whole-organism responses. The focus is on selected peptides that produce complementary neuropharmacological actions on behavior, endocrine secretions and autonomic nervous activity.

Central and peripheral injections of the 5-HT2 agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, modify cardiovascular function through different mechanisms

The mechanisms underlying the cardiovascular effects of central and peripheral administration of the 5-HT2 (serotonin) receptor agonist (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI) were studied in conscious rats. Intravenous (10-1000 nmol/kg) and i.c.v. (3-300 nmol) administration of DOI produced dose-related elevations of arterial pressure without altering heart rate except after injection of the highest doses. Pretreatment with xylamidine tosylate, a 5-HT2 receptor antagonist that does not cross the blood-brain barrier, blocked the pressor response to i.v., but not i.c.v., administration of equivalent doses of DOI. Pretreatment with the vasopressin receptor antagonist d(CH2)5Tyr(Me)AVP significantly reduced the pressor response to i.c.v., but not i.v., administration of DOI. Prior ganglionic blockade with chlorisondamine amplified the pressor response to both i.v. and i.c.v. administration of DOI. Pretreatment with a combination of chlorisondamine, xylamidine and d(CH2)5Tyr(Me)AVP abolished the pressor response to i.c.v. administration of DOI. Thus, the pressor response to i.v. administration of DOI was mediated at sites outside the blood-brain barrier, most likely at vascular 5-HT2 receptors, and was not secondary to vasopressin release. Inappropriate heart rate changes attended the pressor responses to i.v. administration of DOI, suggesting an action at extravascular sites. The pressor response to i.c.v. administration of DOI resulted from a combination of vasopressin release, modulation of autonomic nervous outflow and some leakage into the periphery.

Differentiated hemodynamic responses to central versus peripheral administration of corticotropin-releasing factor in conscious rats

Corticotropin-releasing factor (CRF) modifies cardiovascular function and hemodynamic status after administration into the central nervous system and into the peripheral circulation. The mechanisms by which CRF alters arterial pressure and heart rate have been examined in detail whereas little information exists regarding the processes mediating CRF-induced changes in regional blood flow. Therefore, studies were performed in conscious, unrestrained Sprague-Dawley rats to examine potential mechanisms underlying the regional hemodynamic effects of intracerebroventricular versus intravenous administration of CRF. Intracerebroventricular administration of CRF increased arterial pressure, heart rate, and mesenteric vascular resistance while decreasing iliac vascular resistance. Intravenous pretreatment with the CRF receptor antagonist, alpha-helical CRF9-41, did not alter the cardiovascular and hemodynamic responses to central administration of CRF. In contrast, prior ganglionic blockade prevented CRF-induced responses except for the reduction in iliac vascular resistance. Intravenous administration of CRF reduced arterial pressure and mesenteric vascular resistance, elevated heart rate, and transiently increased iliac vascular resistance. Intravenous pretreatment with alpha-helical CRF9-41 completely abolished the cardiovascular and hemodynamic responses to peripheral administration of CRF. Ganglionic blockade prior to intravenous administration of CRF augmented the reductions in arterial blood pressure and mesenteric vascular resistance, prevented the increase in heart rate, and unmasked a decrease in iliac vascular resistance. The divergent actions and mechanisms of action of CRF on regional hemodynamics when administered peripherally, as opposed to centrally, indicate that this peptide produces different hemodynamic effects that are specific to its site of action.

Central nervous actions of serotonin and a serotonin1A receptor agonist: cardiovascular excitation at low doses

Studies were performed in conscious unrestrained rats to compare the cardiovascular effects of i.c.v. administration of serotonin (5-HT) and the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). Low doses (less than 10 nmol) of 5-HT and 8-OH-DPAT elicited significant elevations of arterial pressure and heart rate. At doses greater than 10 nmol, 5-HT produced pressor responses attended by significant reductions of heart rate whereas 8-OH-DPAT produced significant depressor and bradycardiac responses. Concurrent i.c.v. administration of the nonselective 5-HT receptor antagonist, methiothepin, abolished the cardiovascular responses to a low (1 nmol) and a high (100 nmol) dose of 5-HT and a low (3 nmol) dose of 8-OH-DPAT. In contrast, methiothepin cotreatment did not prevent the reductions of arterial pressure and heart rate induced by a high (100 nmol) dose of 8-OH-DPAT. These results suggest that stimulation of central nervous system 5-HT1A receptors with low doses of 8-OH-DPAT produces cardiovascular activation.

Central regulation of stress responses: regulation of the autonomic nervous system and visceral function by corticotrophin releasing factor-41

Our understanding of the role of CRF in mediating integrated endocrine, autonomic and visceral stress responses is rudimentary at best. Delineating the large number of neurochemical factors that influence the activity of CRF-containing hypophyseotrophic neurones offers one direction for future research in this area. Another approach might be to examine the neuropharmacological actions of transmitters which are co-localized within CRF-containing neurones. For example, CRF and dynorphin-related peptides coexist within a subpopulation of paraventricular neurones (Roth et al, 1983), suggesting the potential for their simultaneous release and possible functional interactions between them. Interestingly, CRF and dynorphin-related peptides exhibit reciprocal actions on the release of each other in vitro and in vivo. CRF stimulates the release of immunoreactive dynorphin from rat hypothalamic slices (Nikolarakis et al, 1986) while dynorphin A1-17 inhibits the basal secretion of immunoreactive CRF from rat hypothalami (Yajima et al, 1986). In vivo experiments demonstrate that i.c.v. administration of dynorphin A1-13 reduces basal and hypotension-induced secretion of CRF into hypophyseal portal blood (Plotsky, 1986). Recent studies suggest that, in addition to their interactions at the level of release, these peptides may also modify the CNS actions of each other on autonomic and cardiovascular function (Overton and Fisher, 1989b). Thus, CRF-induced elevations of arterial pressure, heart rate and plasma catecholamine levels are attenuated by co-administration of low doses of dynorphin A1-17. The reciprocal release actions and neuropharmacological interactions between CRF and dynorphin A1-17 suggest that local integration or perhaps feedback regulation of stress-induced autonomic and cardiovascular responses may be achieved by the co-release of multiple neurotransmitters from a single source. In summary, the combined anatomical, pharmacological and physiological data provide support for the involvement of CRF neuronal systems in mediating the integration of endocrine, autonomic, and visceral functions, particularly in response to stress. Future research in this area may contribute to our understanding of the neurobiology of CRF as well as the CNS mechanisms governing homeostasis.

Effects of exercise training on responses to central injection of CRF and noise stress

The purpose of this study was to test the hypothesis that the cardiovascular and sympathoadrenal responses to acute environmental stress are attenuated by exercise training. Furthermore, we tested the hypothesis that the cardiovascular and sympathoadrenal responses to intracerebroventricular (ICV) administration of corticotropin-releasing factor (CRF) would be attenuated by training. Conscious, unrestrained, male Sprague-Dawley rats assigned to either a treadmill trained (16-26 m/min, 30-60 min/day, 5 days/week) or nontrained (16-26 m/min, 10 min/day, 1 day/week) group were studied. After 8-10 weeks of training, maximal oxygen uptake was significantly higher in the trained (108 +/- 3 ml/kg/min) vs. the nontrained (94 +/- 4 ml/min/kg) group. There were no significant differences in baseline mean arterial pressure, heart rate and plasma catecholamine levels associated with training. Trained rats exhibited significantly attenuated elevations in arterial pressure (20 +/- 3 vs. 36 +/- 2 mmHg for nontrained) and heart rate (-3 +/- 3 vs. 12 +/- 5 beats/min for nontrained) in response to acute noise stress. Twenty minutes after ICV administration of CRF, blood pressure (trained = 119 +/- 2 mmHg, nontrained = 127 +/- 2 mmHg), heart rate (trained = 408 +/- 8 beats/min, nontrained = 424 +/- 10 beats/min), plasma norepinephrine levels (trained = 757 +/- 54 pg/ml, nontrained = 775 +/- 100 pg/ml) and plasma epinephrine levels (trained = 266 +/- 29 pg/ml, nontrained = 225 +/- 42 pg/ml) were significantly elevated in both trained and nontrained groups. CRF-induced elevations of blood pressure, but not heart rate or plasma catecholamine levels, were significantly attenuated in the trained group.(ABSTRACT TRUNCATED AT 250 WORDS)

Central nervous effects of CRF and angiotensin II on cardiac output in conscious rats

Studies were performed to determine whether the central nervous system actions of corticotropin-releasing factor (CRF) and angiotensin II (ANG II) on systemic arterial pressure are mediated, in part, through changes in cardiac output (CO). Changes in CO after intracerebroventricular administration of ANG II and CRF were assessed in conscious unrestrained rats bearing pulsed Doppler flow probes on the ascending aorta. Intracerebroventricular injection of CRF (0.15 nmol) increased arterial pressure (15-20 mmHg), heart rate (70-100 beats/min), and CO (25-35%) without significantly affecting total peripheral resistance. Intracerebroventricular injection of ANG II (0.1 nmol) produced similar elevations of arterial pressure (15-20 mmHg). However, the ANG II-induced pressor response was attended by significant decreases in heart rate (20 beats/min) and CO (10-15%) and significant increases in total peripheral resistance (30-40%). The results of these studies demonstrate that CO, as assessed by pulsed Doppler flow probe methodology, may be influenced significantly and differentially by central nervous system administration of CRF and ANG II.

Gastrointestinal motor effects of corticotropin-releasing factor in mice

The present investigation examined the effects of centrally and peripherally administered corticotropin-releasing factor on gastric emptying and gastrointestinal transit in mice. Corticotropin-releasing factor, given either intracerebroventricularly or intrathecally, caused a dose-dependent inhibition of gastric emptyping and gastrointestinal transit. Intravenous or intraperitoneal administration of corticotropin-releasing factor, while 5- to 7-fold less potent than after central injection, produced an equivalent level of effect. alpha-Helical corticotropin-releasing factor, a corticotropin-releasing factor receptor antagonist, blocked the effects of intracerebroventricularly administered corticotropin-releasing factor when the antagonist was given concurrently by the intracerebroventricular, but not by the intraperitoneal, route. Conversely, corticotropin-releasing factor, when given peripherally, was antagonized equally well by intracerebroventricular or intraperitoneal administration of the antagonist. The inhibition of gastric emptying induced by corticotropin-releasing factor was reduced by pretreatment with the ganglionic blocking agent, chlorisondamine, and in adrenalectomized mice, but this effect was not antagonized by naloxone. These findings provide evidence for an action of corticotropin-releasing factor within the central nervous system, as well as a peripheral site of action, to inhibit gastric emptying in the mouse. The gastrointestinal motor effects of corticotropin-releasing factor are not mediated through opioid mechanisms although their full expression may require intact autonomic innervation and adrenal function.

Central nervous system cardiovascular actions of CRF in sinoaortic-denervated rats

Studies were performed in unrestrained conscious Sprague-Dawley rats to examine the central nervous system (CNS) mechanism by which corticotropin-releasing factor (CRF) produces simultaneous elevations of arterial pressure and heart rate. To test the hypothesis that CRF inhibits ongoing impulse transmission through and/or transmitter release from the CNS terminations of baroreceptor afferents, the cardiovascular effects of intracerebroventricular administration of CRF were compared in rats subjected to prior sham surgery (Sham) or sinoaortic denervation (SAD). Resting levels of arterial pressure and heart rate were elevated after SAD. In addition, SAD resulted in greater chronotropic sympathetic tone and reduced chronotropic parasympathetic tone as assessed by intravenous injections of atropine methyl nitrate and DL-propranolol. Intracerebroventricular administration of CRF in both surgical groups elicited significant increases in arterial pressure and heart rate, although a tendency for reduced tachycardic responses after SAD was apparent. Pretreatment with atropine or propranolol revealed that both the parasympathetic and sympathetic nervous systems contribute to CRF-induced heart rate responses in both surgical groups. These results suggest that ongoing baroreceptor afferent transmission is not requisite for the expression of CRF-induced cardiovascular changes. Thus it is unlikely that CRF elevates arterial pressure and heart rate through an exclusive action at the CNS terminations of baroreceptor sensory fibers.

Cardiovascular responses to exercise in the rat: role of corticotropin-releasing factor

The effects of intracerebroventricular (icv) administration of a corticotropin-releasing factor (CRF) receptor antagonist, alpha-helical CRF, on systemic and regional hemodynamic adjustments to exercise were studied in conscious rats. On consecutive days, rats received saline icv, alpha-helical CRF icv, and no treatment 30 min before treadmill exercise (TMX). Increases in heart rate (HR) and mean arterial pressure (MAP) in response to TMX (16.1-28.6 m/min) were similar after icv administration of saline or no treatment. In rats receiving saline icv or no treatment, estimated vascular resistance increased in the mesenteric and renal regions and declined in the iliac (hindlimb) region. After icv administration of alpha-helical CRF9-41, HR and MAP responses during TMX were significantly attenuated. In addition, TMX-induced elevations of estimated mesenteric vascular resistance and iliac blood flow velocity were blunted after CRF receptor blockade. These altered cardiovascular and hemodynamic responses were ultimately reflected in the animals' compromised ability to run. The results suggest that the central nervous system actions of endogenous CRF are necessary for the full expression of the cardiovascular adjustments to TMX in the conscious rat.

Central nervous system actions of corticotropin-releasing factor on cardiovascular function in the absence of locomotor activity

Studies were performed in conscious and anesthetized Sprague-Dawley rats to examine whether the cardiovascular responses to intracerebroventricular (i.c.v.) administration of corticotropin-releasing factor (CRF) required concomitant locomotor activation. I.c.v. administration of CRF to conscious animals elicited significant increases in arterial pressure, heart rate, mesenteric resistance, and iliac blood flow, as well as intermittent locomotor, grooming and chewing activity. Intravenous infusion of the anesthetic agent, Saffan, at the minimal dose required to abolish locomotor activity caused slight but significant elevations of heart rate and mesenteric vascular resistance. I.c.v. administration of CRF to anesthetized animals produced delayed, yet significant and sustained increases in the heart rate and arterial pressure, without altering regional blood flow. These results demonstrate that locomotor activation is not requisite for the expression of CRF-induced pressor and tachycardic responses. It is concluded that CRF acts within the central nervous system to influence cardiovascular function in the absence of locomotor activity.

Modulation of central nervous system actions of corticotropin-releasing factor by dynorphin-related peptides

Corticotropin-releasing factor (CRF) and dynorphin-related peptides are co-localized within a subset of hypothalamic neurons suggesting the possibility of their co-release. Therefore, studies were performed in conscious unrestrained rats to examine whether dynorphin-related peptides modify the central nervous system (CNS) actions of CRF on sympathetic nervous activity and cardiovascular function. Intracerebroventricular (i.c.v.) administration of dynorphin A1-8 (0.1 and 1.0 nmol) did not alter arterial pressure (AP) or heart rate (HR). I.c.v. injection of dynorphin A1-13 (0.1, 0.3 and 1.0 nmol) produced transient elevations of HR but did not significantly affect AP. I.c.v. administration of dynorphin A1-17 (0.1, 0.3 and 1.0 nmol) elicited delayed (10-15 min) and transient elevations of AP and HR. CRF (0.15 nmol, i.c.v.) produced immediate and sustained elevations of AP, HR and plasma catecholamine levels. Upon simultaneous administration, 0.1 nmol of dynorphin A1-17, but not 0.1 nmol of dynorphin A1-8 or dynorphin A1-13, markedly attenuated CRF-induced elevations of AP, HR, and plasma catecholamine levels. The results suggest that selected dynorphin-related peptides may modify the CNS actions of CRF.

Corticotropin-releasing factor: endocrine and autonomic integration of responses to stress

Corticotropin-releasing factor, a 41-residue peptide, is established as the principal physiological regulator of the pituitary-adrenal axis. The neuroanatomic distribution of corticotropin-releasing factor and its receptors suggests that this peptide may be a neurotransmitter in pathways outside the hypophysiotropic zone. Indeed, corticotropin-releasing factor demonstrates potent neuropharmacological actions that are independent of its pituitary effects. Laurel Fisher reviews the combined anatomical, pharmacological and physiological evidence that supports a role for corticotropin-releasing factor in mediating the integrated endocrine, autonomic and cardiovascular responses to stress.

Central autonomic modulation of cardiac baroreflex by corticotropin-releasing factor

The effects of intracerebroventricular administration of corticotropin-releasing factor (CRF) on baroreflex control of heart rate were studied in conscious, unrestrained rats. Stimulus-response curves relating mean arterial pressure (MAP) to pulse interval were constructed for assessment of baroreflex function. CRF, intracerebroventricularly injected, elicited dose-related reductions of resting pulse interval, response range, and reflex gain and elevations of resting arterial pressure and MAP50 (arterial pressure at midrange). Earlier peripheral blockade of cardiac vagal influences with atropine methyl nitrate greatly attenuated the effects of CRF on resting pulse interval, response range, and reflex gain. In contrast, earlier blockade of cardiac sympathetic influences with intravenous propranolol treatment did not alter the ability of CRF to reduce resting pulse interval, response range, and reflex gain. The central nervous system effects of CRF on cardiac baroreflex function were qualitatively similar to the actions of atropine methyl nitrate. It is concluded that CRF alters transmission in central nervous system pathways mediating baroreceptor-induced activation of cardiac vagal motor neurons.

Family cigarette smoking and test performance by adolescents

This research considers test performance by adolescents as a correlate of cigarette smoking by their families. Scores obtained by adolescents on the California Achievement Test decreased as the amount of cigarette smoking by other members of their families increased. The relationship was not accounted for by active cigarette smoking of the adolescent or by 20 other social and psychological variables.

Use of smokeless tobacco by age, race, and gender in ten standard metropolitan statistical areas of the southeast United States

Most surveys of smokeless tobacco use have been limited to young people, and in the few studies of adults, researchers have not considered age, race, and gender simultaneously, although broad age groups have been used. Data on smokeless tobacco use by race and gender for 5-year age groups up to age 70 and older were compiled from 21,203 households in 10 Standard Metropolitan Statistical Areas of the southeastern United States.

Three mass media campaigns to prevent adolescent cigarette smoking

This article describes behavioral science theory and formative research used to develop television and radio campaigns for preventing the initiation of cigarette smoking among adolescents. It also presents the content and form of the messages, the plans, and the costs for national implementation of the campaigns.

Autonomic and cardiovascular effects of corticotropin-releasing factor in the spontaneously hypertensive rat

Corticotropin-releasing factor (CRF) administered intracerebroventricularly (i.c.v.) produced a greater increase of plasma epinephrine and glucose concentrations in spontaneously hypertensive rats (SHR) than in Wistar-Kyoto (WKY) or Sprague-Dawley (SD) rats. In contrast, CRF given i.c.v. produced significant elevations of mean arterial pressure (MAP) and heart rate (HR) in WKY and SD rats, but not in SHRs. To determine whether the prominent rise of plasma epinephrine levels following CRF administration to SHRs was a unique response to this peptide, two other stimuli for epinephrine secretion were evaluated, i.e. bombesin given i.c.v., and insulin given intravenously (i.v.). In contrast to the apparent enhanced responsiveness of the SHR to CRF, plasma epinephrine levels following either bombesin or insulin administration were similar in SHR, WKY and SD rats. These results demonstrate that the adrenomedullary response to CRF administration in the SHR is of greater magnitude than in WKY or SD rats. In an effort to identify the mechanisms responsible for the differential cardiovascular and adrenomedullary responses to CRF in the SHR versus WKY rat, CRF binding studies were performed. No difference in binding affinity of [125I]CRF or CRF receptor number could be identified in brains from SHR and WKY rats. Thus, CRF influences cardiovascular and adrenomedullary functions in a qualitatively dissimilar fashion in SHR and WKY rats. These differences are not secondary to any measurable alteration in CRF receptor affinity and number in SHR and WKY rats.

Corticotropin-releasing factor: central nervous system effects on baroreflex control of heart rate

The effects of intracerebroventricular injections of corticotropin-releasing factor on baroreflex control of heart rate were examined in conscious, unrestrained rats. Baroreflex control of heart rate was tested by generating stimulus-response curves relating arterial pressure to pulse interval over a wide range of arterial pressures. Administration of corticotropin-releasing factor produced dose-related alterations of pressure-dependent curve parameters, e.g., range, gain and pressure at midrange. These results suggest that corticotropin-releasing factor alters transmission in neural pathways that process baroreceptor information.

Corticotropin-releasing factor receptor antagonist: effects on the autonomic nervous system and cardiovascular function

The corticotropin-releasing factor (CRF) receptor antagonist, alpha-helical [Glu27]-corticotropin-releasing factor 9-41 (CRF 9-41) has been assessed for its ability to modify plasma concentrations of epinephrine and norepinephrine, mean arterial pressure (MAP) and heart rate (HR). Basal concentrations of epinephrine and norepinephrine were not altered by lateral ventricular (icv) administration of CRF 9-41. However, this CRF antagonist, given icv, attenuated the rise of plasma epinephrine following 30% hemorrhage and insulin-induced hypoglycemia. CRF 9-41 did not alter the increased plasma concentrations of epinephrine or norepinephrine following icv administration of bombesin. Icv administration of CRF 9-41 blunted CRF-induced elevation of MAP and HR in normal animals. However, this CRF antagonist did not modify the MAP or HR in spontaneously hypertensive rats. Similarly, this CRF antagonist administered to Sprague-Dawley rats neither prevented the rise of MAP or HR following electrical stimulation of the central nucleus of the amygdala, nor did it affect nitroprusside-induced hypotension and tachycardia.

Glucocorticoid suppression of the sympathetic nervous system and adrenal medulla

Studies were performed to evaluate the effects of glucocorticoids on the activity of the sympathetic nervous system and adrenal medulla. Plasma concentrations of norepinephrine and epinephrine were measured in rats in which endogenous glucocorticoids were removed by bilateral adrenalectomy and in rats to which exogenous glucocorticoids were administered. In intact rats, dexamethasone (2.5, 25 or 250 micrograms) pretreatment suppressed ether vapor-induced elevations of norepinephrine and epinephrine concentrations in plasma. Corticosterone (3 mg/kg), similar to dexamethasone, attenuated the elevation of plasma concentrations of norepinephrine and epinephrine in rats exposed to ether vapor. Glucocorticoids did not alter the elevation of plasma catecholamines stimulated by intracerebroventricular injections of corticotropin-releasing factor or calcitonin gene-related peptide, thus demonstrating functional integrity of the sympathetic nervous system and adrenal medulla. Adrenalectomy resulted in elevation of basal plasma norepinephrine levels and accentuation of ether vapor-induced elevations of plasma norepinephrine concentrations in rats. Dexamethasone (25 ug) administration blunted the effects of adrenalectomy on both basal and ether vapor-stimulated levels of plasma norepinephrine. It is concluded that glucocorticoids acting at as yet undefined sites may be involved in the regulation of sympathetic nervous system and adrenal medullary function.

Central nervous system effects of bombesin on the cardiovascular response to cold exposure

The effects of cold exposure on mean arterial pressure (MAP), heart rate (HR) and oxygen consumption (VO2) were examined in conscious, unrestrained rats receiving intracerebroventricular (i.c.v.) injections of bombesin or appropriate control solutions. Cold exposure elicited significant elevations of MAP, HR and VO2 in control-treated rats. I.c.v. administration of bombesin produced dose-related suppressions of cold-induced elevations of HR and VO2, but not MAP. The central nervous system (CNS)-selective somatostatin analog, ODT8-SS, injected i.c.v., reversed the effects of bombesin on HR and VO2 during cold exposure. Intravenous administration of atropine methyl nitrate did not antagonize the effects of bombesin on HR and VO2 during cold exposure. HR and VO2 were strongly correlated in bombesin-treated rats suggesting that this peptide may prevent cold-induced elevations of VO2 through a CNS action on cardiac function.

Corticotropin-releasing factor, sauvagine, and urotensin I: effects on blood flow

Corticotropin-releasing factor (CRF), sauvagine (SVG), and urotensin I (UI) were tested for their effects on superior mesenteric blood flow in conscious dogs. Intravenous (iv) administration of CRF, SVG, and UI induced an immediate rise of mesenteric blood flow that was associated with a decrease in mean arterial pressure and an increase in heart rate. Intracerebroventricular (ICV) injection of SVG and UI, but not CRF, rapidly (within 5 min after injection) elicited a long (90 min) elevation of mesenteric blood flow. Central administration of these peptides induced a delayed rise in heart rate and slightly elevated mean arterial pressure. The finding that CRF given ICV did not increase mesenteric blood flow could not be explained by the release of vasoactive agents such as vasopressin, epinephrine, or norepinephrine. After injection of CRF, SVG, and UI, plasma concentrations of CRF-, SVG-, and UI-like immunoreactivity did not increase as determined by radioimmunoassay. These results indicate that SVG and UI, but not CRF, administered ICV produce a long increase of mesenteric blood flow in conscious dogs. Because iv SVG and UI decrease mean arterial pressure and ICV SVG and UI increase mean arterial pressure and do not cause an increase in SVG- and UI-like immunoreactivity in the peripheral circulation, it is proposed that SVG and UI injected into the third cerebral ventricle act within the central nervous system to increase superior mesenteric blood flow in the dog.