Noradrenaline-induced prostaglandin production by sympathetic postganglionic neurons is mediated by alpha 2-adrenergic receptors

In this study we have demonstrated that noradrenaline increases the levels of prostaglandin E2 and prostaglandin I2 (detected as the stable metabolite 6-keto-prostaglandin F1 alpha) synthesized by homogenates of superior cervical ganglia from the adult rat. This noradrenaline-induced prostaglandin production was further characterized: (a) Selective destruction of adrenergic sympathetic postganglionic neurons in the ganglia using 6-hydroxydopamine abolished both basal and stimulated prostaglandin production. (b) Elimination of preganglionic cholinergic sympathetic nerve terminals in the ganglia had no effect. (c) Mepacrine (a phospholipase inhibitor) and indomethacin (a cyclooxygenase inhibitor) attenuated both basal and stimulated prostaglandin production. (d) Yohimbine, but not prazosin, suppressed the noradrenaline dose-response curve for prostaglandin production. The results of these experiments show that, in vitro, noradrenaline stimulates de novo synthesis of prostaglandin E2 and prostaglandin I2 by sympathetic postganglionic neurons. This stimulation by noradrenaline appears to result from action at an alpha 2-adrenergic receptor.

Lack of effect of ephedrine on opiate analgesia

Opiate-adrenomimetic interaction was investigated by studying the effect of the adrenomimetic agent, ephedrine, on the analgesia produced by intravenous placebo and that produced by the predominantly kappa opiate agonist, pentazocine, in patients with dental postoperative pain. Ephedrine did not significantly affect the analgesia of intravenous placebo or of pentazocine. These results contrast with earlier studies demonstrating enhancement of opiate analgesia by other adrenomimetics. Further clinical studies are needed to delineate the specificity of opiate-adrenomimetic interaction.

Delayed activation of nociceptors: correlation with delayed pain sensations induced by sustained stimuli

1. In this study we used psychophysical experiments in humans and behavioral and electrophysiological studies in rats to evaluate nociceptive and C-fiber mechanoheat nociceptor (C-MH) responses to sustained mechanical stimuli that are initially nonpainful or nonnoxious. 2. In normal rat skin, sustained subthreshold mechanical stimuli activate C-MHs (n = 36) with a delayed onset that parallels the delayed pain sensation recorded in human psychophysical tests. 3. The subthreshold stimuli did not induce a decrease in mechanical threshold (n = 11), and the effect of the subthreshold stimulus on latency to firing of C-MHs (n = 6) persists for a very short time after the stimulus is removed (less than 10 s). 4. Intradermal injection of prostaglandin E2 (PGE2; 100 ng), which induced a significant decrease in the mechanical threshold of C-MHs (n = 7), had no effect on the latency of the delayed activation of C-MHs. Also, indomethacin, which inhibits the synthesis of prostaglandins, had no effect on the latency of the delayed paw-withdrawal response in the behavioral test. 5. Intradermal injection of the calcium ionophore A23187 significantly reduced the latency of the delayed activation of C-MHs (n = 6) the calcium chelator Quin 2 (n = 6) significantly increased the latency. A23187 and Quin 2 had similar effects on the latencies to paw withdrawal in behavioral tests. The sensitization of C-MHs (n = 9) by PGE2 was not, however, affected by Quin 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathetic neuron factors involved in bradykinin-induced plasma extravasation in the rat

Previous studies have demonstrated that bradykinin (BK) produces a sympathetically dependent plasma extravasation into the rat knee joint which is, in part, dependent upon the production of a prostaglandin. In the present study, co-administration of the specific prostaglandin, PGE2, markedly enhanced the BK-induced plasma extravasation. In this study we also report that after chemically induced sympathectomy, by chronic pretreatment with 6-hydroxydopamine (6-OHDA), both the plasma extravasation produced by BK and the enhancing effect of PGE2 are markedly attenuated. Plasma extravasation induced by PGE2 alone was small and was not significantly attenuated by sympathectomy. We conclude that BK-induced extravasation involves production of at least two sympathetic postganglionic neuron (SPGN) terminal-dependent factors, one of which is a cyclo-oxygenase product of arachidonic acid metabolism, probably PGE2, (Coderre et al., J. Neurophysiol., 62 (1989) 45-58) and another that is unidentified.

A possible indicator of functional pain: poor pain scale correlation

We studied correlations of pain measures in patients with either inflammatory bowel disease (IBD), a disease with a clear organic cause, or irritable bowel syndrome (IBS), a functional pain syndrome in which there is little demonstrable pathology. Correlations were determined between measures on the visual analogue scale (VAS) and on the McGill Pain Questionnaire (MPQ). The VAS score and present pain intensity scale (PPI) of the MPQ correlated well in the organic IBD but correlated poorly in the functional IBS. Differences in correlation between the VAS and PPI scores in functional versus organic disease did not appear to be due to altered sensory and affective pain components. This finding is similar to what we observed in our previous study of organic and functional pain syndromes in the musculoskeletal system. Correlations between the other measures are also discussed.

Different mechanical transduction mechanisms for the immediate and delayed responses of rat C-fiber nociceptors

1. In this electrophysiological study, action potentials from single C-fibers were recorded in fine filaments teased from the rat saphenous nerve. We evaluated the effect of pharmacological agents on the responses of C-fiber mechanoheat nociceptors (C-MH; n = 53) after sustained suprathreshold and subthreshold stimuli. 2. Sustained suprathreshold mechanical stimuli elicit an immediate burst of activity that quickly adapts to a low-level firing that is maintained during the stimulus. Sustained subthreshold stimuli activate C-MHs after a delay and elicit a constant, low-level firing. 3. Gentamicin, a known suppressor of mechanosensory cell activity, blocked the initial rapid burst response to suprathreshold stimuli (n = 11) but had no effect on the adaptive low-level firing. The latency of the delayed activation of C-MHs induced by sustained subthreshold stimuli was not affected by gentamicin. 4. Sphingosine, a protein kinase inhibitor, increased the latency of the delayed activation of C-MHs (n = 7) to sustained subthreshold stimuli; phorbol 12-myristate 13-acetate (TPA), a protein kinase C activator, decreased the latency of the delayed activation of C-MHs (n = 9); and 4 alpha-phorbol, an inactive isomer of TPA, had no effect on the latency of the delayed activation (n = 7). Sphingosine, TPA, and 4 alpha-phorbol had no affect on the initial burst response induced by suprathreshold stimuli. 5. K+ channel blockers, 4-aminopyridine (n = 9) and noxiustoxin (n = 5), decreased the latency of the delayed activation of C-MHs to sustained subthreshold stimuli but had no effect on the initial burst response of C-MHs to suprathreshold stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the antinociceptive and motor effects of intrathecal opioid agonists in the rat

This study compared the antinociceptive and motor effects produced by intrathecal administration of selective mu-, delta-, and kappa-opioid receptor agonists in the rat. Changes in nociceptive threshold were measured using the Randall-Selitto paw-withdrawal test and changes in motor coordination were evaluated using the rotarod treadmill test. Each opioid agonist produced statistically significant, dose-dependent increases in mechanical nociceptive thresholds compared to vehicle controls. In the motor coordination studies, DAMGO and DPDPE, but not U50,488H, produced statistically significant decreases in rotarod performance scores compared to vehicle controls. The results of these studies suggest that motor side-effects produced by opioid agonists need to be considered when interpreting the results of antinociceptive tests that are dependent on a normally functioning motor system.

Hyperalgesia induced in the rat by the amino-terminal octapeptide of nerve growth factor

Nerve growth factor (NGF) in the mouse submandibular gland undergoes cleavage of its amino-terminal octapeptide when salivation is induced by epinephrine. The significance of this event is uncertain; cleaved NGF demonstrates bioactivity and no function has been attributed to the octapeptide produced (NGF-OP; Ser-Ser-Thr-His-Pro-Val-Phe-His). Enzyme inhibition studies indicating structural relatedness of NGF-OP and bradykinin (BK) prompted us to determine whether NGF-OP would elicit BK-like actions. We found that like BK, NGF-OP induced a decrease in mechanical nociceptive threshold (i.e., produced hyperalgesia) in the hairy skin of the rat. This effect was dose-dependent and sequence-specific; like BK it was attenuated by sympathectomy and indomethacin pretreatment. However, NGF-OP actions appeared to be distinct from those for BK in that tissue injury was required for NGF-OP to induce hyperalgesia. Furthermore, we found no evidence that NGF-OP bound to or activated BK receptors. Our data indicate that NGF-OP is a distinct mediator of hyperalgesia. We suggest that NGF-OP alters pain threshold in the injured target regions of NGF-responsive neurons.

Postnatal development of neurogenic inflammation in the rat

We have studied the development in the rat of neurogenic inflammatory mechanisms that mediate cutaneous plasma extravasation. At birth and at postnatal day 10, intradermal injection of substance P, histamine, and bradykinin produced no significant plasma extravasation. At day 13 through adulthood (days 42-49), all test agents produced significant plasma extravasation which increased with increasing age. In the adult rat, pretreatment with 6-hydroxydopamine, to eliminate sympathetic postganglionic nerve terminals, attenuated the plasma extravasation elicited by substance P, histamine and bradykinin. The possible role of the sympathetic postganglionic neuron in the age-dependent changes in neurogenic inflammation is discussed.

Purinergic regulation of bradykinin-induced plasma extravasation and adjuvant-induced arthritis in the rat

We assessed the contribution of ATP and adenosine (i) to a major sign of acute inflammation, plasma extravasation (PE), in the rat knee joint and (ii) to the severity of joint injury in adjuvant-induced experimental arthritis, a chronic inflammatory disease. PE induced by local infusion of bradykinin, which we have previously shown to depend on the sympathetic postganglionic neuron terminal, was markedly enhanced by coinfusion of either ATP or the adenosine A2-receptor agonist 2-[4-(2-carboxyethyl)phenylethylamino]-5'-N-ethylcarboxamidoadenos ine. Bradykinin-induced PE was inhibited by coinfusion of the ATP receptor antagonist adenosine 5'-[alpha,beta-methylene]triphosphate, the A2-receptor antagonist 3-(5H-thiozolo[2,3b]quinazolin-3-yl)phenol monohydrochloride, or the adenosine A1-receptor agonist N6-cyclopentyladenosine. The joint injury associated with experimental arthritis, which is reduced in severity in sympathectomized rats, was also markedly attenuated by daily administration of either ATP (40% reduction) or adenosine (55% reduction). These results demonstrate that the purines ATP and adenosine (acting at the A2 receptor), cotransmitters in the sympathetic postganglionic neuron terminal, enhance bradykinin-induced sympathetic postganglionic neuron terminal-dependent PE but inhibit the joint injury of arthritis. These opposing purinergic effects on PE and joint injury suggest that enhanced PE protects against joint injury.

Granulocyte-macrophage colony-stimulating factor mitigates the neutropenia of combined interferon alfa and zidovudine treatment of acquired immune deficiency syndrome-associated Kaposi's sarcoma

The combined use of zidovudine (ZDV) and interferon (IFN) alfa-2a has been shown to have antiretroviral and antitumor potential benefit in the treatment of acquired immune deficiency syndrome (AIDS)-associated Kaposi's sarcoma (KS). However, the clinical use of this combination is frequently complicated by the overlapping myelotoxicity of these agents. We report here the results of a phase I/II study in which granulocyte-macrophage colony-stimulating factor (GM-CSF) was used for those KS patients who became neutropenic while receiving ZDV (1,200 mg/d) and IFN (9 x 10(6) U/d). Nineteen of 29 patients (66%) developed an absolute neutrophil count (ANC) of less than 1,000 cells per cubic millimeter and were begun on GM-CSF. All experienced a prompt increase in the ANC. Those patients receiving GM-CSF/ZDV/IFN alfa-2a had an improved end of study ANC when compared with the ZDV/IFN alfa-2a group, but did not have an increased rate of tumor response, end of study CD4 cell count, or improvement in any other hematologic variable. The use of GM-CSF was not associated with increased toxicity and, in particular, was not associated with a change in serum human immunodeficiency virus (HIV) p24 antigen. Tumor response was noted in 50% of the assessable patients (33% overall) despite "high-risk" characteristics in 80%. Of the responding patients, seven were on GM-CSF and might have otherwise required an alteration in ZDV/IFN alfa-2a dose level. Further study of GM-CSF as an alternate to dose modification of this (ZDV/IFN alfa-2a) and other combination therapies for AIDS patients is warranted.

The contribution of the nervous system to inflammation and inflammatory disease

Recent studies have identified a major contribution of the nervous system to inflammation and to inflammatory disease. In particular, substances released from the peripheral terminals of small diameter primary afferent fibers and from sympathetic postganglionic nerve (SPGN) terminals have been implicated in several of the major components of acute inflammation (e.g., vasodilatation and plasma extravasation) as well as in the regulation of tissue injury in an inflammatory disease model, experimental arthritis in the rat. Although the release of peptides from primary afferent terminals has received the most attention, our studies have established an important contribution of mast cells and the SPGN terminals to acute inflammation. We describe studies which indicate that plasma extravasation provoked by activation of small diameter primary afferents in the knee joint of the rat involves a cascade of events in which the mast cell and then the sympathetic terminal are sequentially activated. Our studies indicate that release of prostaglandins, but neither norepinephrine nor neuropeptide Y, from the SPGN terminal contributes to increased plasma extravasation. Although activation of the SPGN terminal (via the mast cell) or more directly, via injection of bradykinin, increased plasma extravasation, surgical or pharmacological sympathectomy decreased the severity of experimental arthritis. In related studies we demonstrated that adrenal medullary-derived epinephrine can exacerbate arthritis through a beta-receptor-mediated regulation of the release of an as yet unidentified substance(s) from the SPGN terminal. Our results raise important questions as to whether acute inflammation contributes to tissue repair or to further injury in the setting of disease.

Retinohypothalamic tract in the female albino rat: a study using horseradish peroxidase conjugated to cholera toxin

There are several anatomically and functionally distinct retinofugal pathways, one of which is the retinohypothalamic tract (RHT). In this study, horseradish peroxidase conjugated to cholera toxin (CT-HRP), a sensitive neural tracer, was employed to describe the RHT in the female albino rat. Following uniocular injection of CT-HRP, both medial and lateral components of the RHT were evident. The medial component swept caudally into and through the suprachiasmatic nucleus (SCN) and dorsally to the subparaventricular zone. Terminal label was seen in the medial preoptic region, peri-SCN area, retrochiasmatic area, periventricular nucleus, anterior and central parts of the anterior hypothalamic area, and the subparaventricular zone. In contrast to the more focused and symmetrical medial component, the lateral component was diffuse with light terminal label in the lateral preoptic region, olfactory tubercle, lateral hypothalamus, supraoptic nucleus, and medial and posteroventral medial amygdaloid nuclei. The striking exception to this diffuse pattern of the lateral component was an extremely dense columnar terminal field over the dorsal border of the supraoptic nucleus. Whereas the intensity of label in terminal fields of the medial component was often similar on the sides ipsilateral and contralateral to the injection, the lateral component was consistently asymmetrical with greater labeling on the side contralateral to the injection. In addition, a light projection arrived at several thalamic nuclei by returning toward the thalamus from the tectal or pretectal areas via stria medullaris, and thus was not a part of the RHT. Implications for circadian as well as noncircadian photobiologic effects are discussed.

Kappa- and delta-opioids block sympathetically dependent hyperalgesia

Direct hyperalgesia induced by prostaglandin E2 (PGE2) can be blocked by mu- but not delta- or kappa-opioids. However, there is evidence that kappa- and delta-opioid receptors are located on sympathetic postganglionic neuron (SPGN) terminals, which mediate bradykinin (BK) hyperalgesia via SPGN-terminal-dependent production of PGE2. Therefore, we evaluated the antinociceptive effect of delta- and kappa-opioids on BK hyperalgesia. We demonstrate that the mechanical hyperalgesia induced by intradermal injection of BK can be blocked by the kappa-opioid agonist trans-3,4-dichloro-N-methyl-N[2-(-pyrrolidinyl)cyclo-hexyl] benzeneacetamide (U50,488H) and by the delta-opioid agonist (D-Pen2,5)-enkephalin (DPDPE), as well as the mu-opioid agonist Tyr-D-Ala-Gly-NMe-Phe-Gly-ol(DAMGO). Pertussis toxin prevented the inhibition of BK-induced hyperalgesia by U50,488H, DPDPE, or DAMGO. We conclude that the observed peripheral analgesic effects of kappa- and delta-opioid agonists result from actions upon SPGN terminals and that these effects are mediated by inhibitory G-proteins.

High-dose epinephrine acts at alpha 2-adrenoceptors to suppress experimental arthritis

This study assessed the receptor site at which high systemic doses of epinephrine act to reduce the severity of adjuvant-induced arthritis in the rat. To this end we examined the effect of selective adrenergic antagonists on the reduction of arthritis by epinephrine, and also assessed whether high doses of selective adrenergic agonists mimicked the effect of epinephrine. The decrease in arthritis induced by epinephrine (0.5 mg/kg in chronic implant injected every 3 days) was significantly antagonized by the selective alpha 2-adrenergic antagonist, yohimbine, but not by selective alpha 1 (prazosin), beta 1 (metoprolol) or beta 2 (butoxamine) antagonists. In addition, chronic infusion of the alpha 2-adrenergic agonist clonidine, but not selective alpha 1 (phenylephrine), beta 1/beta 2 (isoproterenol) or beta 2 (salbutamol) agonists, resulted in decreased arthritis severity. These data suggest that the suppressive effect of high-dose epinephrine on joint injury in experimental arthritis is mediated by action at the alpha 2-adrenergic receptor.

Further confirmation of the role of adenyl cyclase and of cAMP-dependent protein kinase in primary afferent hyperalgesia

Recent evidence has suggested that cAMP plays a role as a second messenger in the decrease in nociceptive threshold (or hyperalgesia) produced by agents acting on primary afferent terminals. In support of this hypothesis we report that intradermal injection of a direct activator of adenyl cyclase, forskolin, produces a dose-dependent hyperalgesia in the rat. The duration of this hyperalgesia was prolonged by the phosphodiesterase inhibitors, isobutylmethylxanthine and rolipram. Forskolin hyperalgesia was antagonized by the Rp isomer of cyclic adenosine-3'5'-monophosphothioate, an analog of cAMP that prevents the phosphorylation of the cAMP protein kinase. The Rp isomer of cyclic adenosine-3'5'-monophosphothioate also inhibited the hyperalgesia induced by a membrane-permeable analogue of cAMP, 8-bromocyclic adenosine monophosphate, as well as the hyperalgesia induced by agents that are presumed to act directly on primary afferent nociceptors: prostaglandin E2, prostaglandin I2, (8R,15S)-dihydroxyicosa(5E-9,11,13Z)tetraenoic acid; and the adenosine A2-agonist 2-phenylaminoadenosine. Although the cAMP second messenger system contributes to primary afferent hyperalgesia, we found no evidence for a contribution of protein kinase C. Thus, hyperalgesia induced by prostaglandin E2, prostacyclin (prostaglandin I2), (8R,15S)-dihydroxyicosa(5E-9,11,13Z)tetraenoic acid, the adenosine A2-agonist 2-phenylaminoadenosine, 8-bromocyclic adenosine monophosphate and the direct activator of adenyl cyclase, forskolin, were not significantly attenuated by the selective inhibition of protein kinase C by the 19-31 fragment of protein kinase C. Two other inhibitors of protein kinase C, sphingosine and staurosporine, also failed to attenuate prostaglandin E2-induced hyperalgesia.

The contributions of interpersonal conflict to chronic pain in the presence or absence of organic pathology

This study investigated the influences of social support and interpersonal conflict on chronic pain in patients with arthritis or with myofascial disorders. Measures of social support, conflict, and pain were drawn from subscales of the McGill Pain Questionnaire, the Multidimensional Pain Inventory, the Family Environment Scale, and the Interpersonal Relationship Inventory. Patients with myofascial disorders reported significantly worse pain (sensory and affective), higher depression scores, more interpersonal conflict, and less support from others than patients with arthritis, but did not differ from them on personality traits. Also, the contributions of conflict to pain were found to depend on the nature of the chronic disorder and on the source of the conflict, i.e., significant other, family, or social network members. For patients with arthritis, less intense pain (sensory and affective) was associated with higher family conflict. Less intense sensory pain in arthritis was also associated with more punishing responses from the significant other to pain. For patients with myofascial disorders, more intense affective pain was associated with higher social network conflict. Social support did not significantly contribute to pain for either group. Thus, chronic painful disorders may differ on the influences that social relationships have on pain. The implications of these differences for treatment are discussed.

The antinociceptive action of supraspinal opioids results from an increase in descending inhibitory control: correlation of nociceptive behavior and c-fos expression

In an earlier report, we demonstrated that subcutaneous injection of formalin in the rat hindpaw evokes a characteristic pattern of expression of the fos protein product of the c-fos protooncogene in spinal cord neurons, and that systemic morphine reversed the fos-like immunoreactivity in a dose-dependent, naloxone-reversible manner. The present study compared the effects of intracerebroventricular administration of the mu-selective opioid ligand [D-Ala2, NMe-Phe4, Gly-ol5] enkephalin, on the pain behavior and spinal cord fos-like immunoreactivity produced by subcutaneous formalin. Formalin injection produced a biphasic pain behavioral response which lasted about 1 h. There was a significant correlation between the formalin pain score and overall fos-like immunoreactivity in the lumbar enlargement. The greatest numbers of labeled cells and most intense fos-like immunoreactivity were found in laminae I, IIo and V of the L4-5 segments, ipsilateral to the formalin-injected paw. Considerable staining was also found in the ipsilateral ventral horn laminae VII and VIII. [D-Ala2, NMe-Phe4, Gly-ol5]enkephalin produced a dose-related, naloxone-reversible inhibition of both the formalin-evoked pain behavior and fos expression in the cord. The behavioral response to formalin, however, could be completely blocked without eliminating the expression of fos in spinal neurons. Moreover, subpopulations of neurons were differentially regulated. Thus, 100% inhibition of pain behavior was produced at a dose of [D-Ala2, NMe-Phe4, Gly-ol5]enkephalin which reduced fos-like immunoreactivity in the superficial laminae by only 64% and in the neck and ventral cord by 85%. Furthermore, the dose of [D-Ala2, NMe-Phe4, Gly-ol5]enkephalin which produced approximately 50% inhibition of fos-like immunoreactivity in the neck and ventral regions of the spinal cord was without effect in the superficial dorsal horn. Since the potencies for inhibition of pain behavior and fos-like immunoreactivity in the neck and ventral horn were comparable, these data suggest that the activity of neurons in these regions is directly related to the pain behavior produced by nociceptive inputs. Finally, we found that bilateral, midthoracic lesions of the dorsal part of the lateral funiculus blocked both the antinociception and fos suppression produced by intracerebroventricular [D-Ala2, NMe-Phe4, Gly-ol5]enkephalin. These results are consistent with the hypothesis that the analgesic action of supraspinally administered opiates results from an increase in descending inhibitory controls that regulate the firing of subpopulations of spinal cord nociresponsive neurons.

Neutrophils contribute to sympathetic nerve terminal-dependent plasma extravasation in the knee joint of the rat

Infusion of bradykinin or 6-hydroxydopamine into the knee joint of the rat activates sympathetic postganglionic nerve terminals and increases plasma extravasation, a major sign of acute inflammation. Since bradykinin attracts and activates neutrophils in vivo and since neutrophils can release factors leading to plasma extravasation, we evaluated the contribution of the neutrophil to bradykinin-induced plasma extravasation. We report that perfusion of bradykinin into the rat knee joint produces a prolonged increase in plasma extravasation which is markedly reduced not only by sympathectomy (chronic pretreatment with systemic 6-hydroxydopamine) but also by depletion of circulating polymorphonuclear leukocytes (intravenous infusion of hydroxyurea combined with intraperitoneal glycogen). Depletion of polymorphonuclear leukocytes also reduced the plasma extravasation induced by intra-articular infusion of 6-hydroxydopamine, which acutely activates sympathetic postganglionic terminals. We next tested whether attraction of neutrophils into the joint, in the absence of bradykinin, was sufficient to enhance plasma extravasation. Although the classical neutrophil attractant glycogen attracted neutrophils into the knee joint, it did not increase plasma extravasation. Co-infusion of bradykinin and glycogen into the knee joint, however, provoked plasma extravasation that was significantly greater than that produced by bradykinin alone. We hypothesize, therefore, that bradykinin not only attracts neutrophils but also activates them, by an as yet undefined mechanism that requires the sympathetic terminal. The activated neutrophils release factors that lead to plasma extravasation. The next series of studies evaluated the role of the sympathetic nervous system in neutrophil attraction in vivo by bradykinin and glycogen. Since quantification of neutrophil attraction was not possible in the knee joint, we performed these studies in the peritoneal cavity, a site where neutrophils are readily attracted.(ABSTRACT TRUNCATED AT 250 WORDS)

Increasing sympathetic nerve terminal-dependent plasma extravasation correlates with decreased arthritic joint injury in rats

This study compared the pharmacology of adrenergic agents that influence plasma extravasation in normal animals with those agents that influence tissue injury in an inflammatory disease model. Specifically we studied the effects of beta 2- and alpha 2-adrenergic receptor agonists and antagonists on bradykinin-induced plasma extravasation in normal Sprague-Dawley rats and on joint injury in rats with experimental arthritis. Plasma extravasation induced by infusion of bradykinin in the rat knee joint was attenuated by the beta 2-agonist salbutamol or by the alpha 2-antagonist yohimbine, and was enhanced by the beta 2-antagonist, ICI-118,551, or by the alpha 2-agonist, clonidine. In rats that had undergone chemical symphathectomy, bradykinin-induced plasma extravasation was markedly reduced, and there was no enhancement of bradykinin-induced plasma extravasation by either ICI-118,551 or clonidine. Although ICI-118,551 and clonidine enhanced bradykinin-induced plasma extravasation, these drugs significantly reduced joint injury in rats with adjuvant-induced arthritis. Neither salbutamol nor yohimbine, however, significantly increased joint injury in the arthritic rats, presumably because arthritis severity is already high in these animals. Consistent with this hypothesis, both salbutamol and yohimbine did significantly increase the joint injury associated with experimental arthritis in Wistar-Kyoto rats, a strain which develops a mild adjuvant arthritis. The fact that increased plasma extravasation is associated with decreased arthritis severity suggests that plasma extravasation, a major sign of acute inflammation, contributes to tissue reparative processes.

GM-CSF as an alternative to dose modification of the combination zidovudine and interferon-alpha in the treatment of AIDS-associated Kaposi's sarcoma

Combined zidovudine (ZDV) and interferon-alpha (IFN) is an appealing therapy for AIDS-associated Kaposi's sarcoma because of the antiretroviral as well as antitumor potential of this combination. Overlapping myelotoxicity of these agents, however, frequently complicates their clinical use. This phase I/II study was undertaken to test the safety and efficacy of granulocyte-macrophage colony stimulating factor (GM-CSF) in those patients who became neutropenic while receiving ZDV (1,200 mg/day) and IFN (9 MU/day). Despite a "high-risk" population of patients, the tumor response rate among evaluable patients was 50% (33% overall). Sixty-four percent of patients required GM-CSF and all patients receiving GM-CSF had a prompt improvement in their absolute neutrophil count (ANC). The use of GM-CSF was associated with an improved end of study ANC (p less than 0.05), but was not associated with tumor response, CD4 count improvement, or improved change in hemoglobin concentration. GM-CSF/ZDV/IFN was not associated with increased toxicity over ZDV/IFN; however, two unusual events occurred in the GM-CSF/ZDV/IFN group: erythema multiforme and glucose intolerance. Dose-limiting thrombocytopenia and anemia were seen in two patients and anemia in one patient on GM-CSF/ZDV/IFN. No consistent alterations in serum HIV p24 antigenemia were noted in either group. The use of GM-CSF mitigated the neutropenia of combined ZDV and IFN. Further study evaluating the utility of this hematopoietic growth factor in combination therapies for AIDS patients is warranted.

Effects of cyclooxygenase products of arachidonic acid metabolism on cutaneous nociceptive threshold in the rat

The nonsteroidal anti-inflammatory drugs are presumed to produce their analgesic effects by inhibiting the cyclooxygenase catalyzed metabolism of arachidonic acid to hyperalgesic prostanoids. This study examined the hyperalgesic effect of a range of prostaglandins. We found, employing the rat paw-withdrawal test, that while intradermal injection of the known hyperalgesic prostaglandins, E2 and I2, produced hyperalgesia, other primary metabolites of the cyclooxygenation of arachidonic acid (prostaglandin F2 alpha, prostaglandin D2, thromboxane B2 and 12(S) hydroxyheptadecatrienoic acid) did not produce hyperalgesia. We conclude that prostaglandin E2 and prostaglandin I2 are the main hyperalgesic metabolites of the cyclooxygenase pathway of arachidonic acid.

The circadian activity rhythms of rats with mid- and parasagittal 'split-SCN' knife cuts and pinealectomy

To explore the multioscillator nature of the neurohumoral circuitry controlling the expression of circadian rhythmicity, rats' wheel running circadian activity rhythms were compared following sagittal knife cuts in the region of the suprachiasmatic nucleus (SSCN), following pinealectomy (PX) and following the combination of SSCN and PX. 25% of animals with knife cuts that passed through one SCN had disturbed running activity under constant illumination; rhythmic disturbances were seen neither in animals with sham knife cuts nor in rats with knife cuts on the midline or lateral to the SCN. Animals with both SSCN and PX were twice as likely to show severe rhythmic disruptions under free-running conditions as rats with SSCN and sham PX. Rats with PX and sham SSCN did not display disrupted activity rhythms. When animals with PX alone or SSCN alone were first observed under free-running conditions and then subjected to a second surgical procedure so that all animals underwent both PX and SSCN, all PX and most SSCN animals demonstrated coherent activity rhythms after the first operation, but 35% showed disruptions in circadian activity patterns only following the second surgery. The activity rhythms of rats with knife cuts placed either on the midline or lateral to the SCN did not deteriorate when combined with PX. Rats with coherent rhythms following knife cuts damaging one SCN had rhythm disruptions after the addition of PX. The effects of pinealectomy may indicate that the pineal gland plays a role in maintaining the coupling relationships in the multioscillator system controlling circadian activity rhythms. The results of this study also suggest that neither the direct commissural connection of the SCNs nor the humoral output of the pineal gland is indispensable for the expression of coherent circadian activity rhythms in the rat.