P-Chloramphetamine: Selective neurotoxic action in brain.

Injection of 2.5,5, 10, or 20 milligrams of p-chloroamphetamine per kilogram of body weight into rats produced evidence of cytopathological changes in sections of brain stained by a Nissl or silver method. As early as 1 day after drug injection cells demonstrated an intense Nissl staining, intense argyrophilia, cellular shrinkage, and perineuronal spaces. At 30 days after injection both stains revealed cellular debris and glial reactions characteristic of cellular dissolution. The neurotoxic effects of 2.5, 5, or 10 milligrams of p-chloroamphetamine per kilogram were primarily restricted to an area of the ventral midbrain tegmentum corresponding to the distribution of the B-9 serotonergic cell group. After 20 milligrams of p-chloroamphetamine per kilogram there was also evidence of neurotoxic effects on cells within the substantia nigra. These results confirm previous suggestions that the long-term reduction in serotonin content of brain, tryptophan-5-hydroxylase activity, and uptake of serotonin after injection of p-chloroamphetamine is due to a neurotoxic effect of the drug or some metabolite on serotonergic cell bodies.

A newly defined property of somatotropin: priming of macrophages for production of superoxide anion.

Macrophages can be activated to produce reactive oxygen intermediates, such as superoxide anion (O2-), which are responsible for intracellular killing of pathogenic microbes. Treatment with either native or recombinant somatotropin augmented the production of O2- by both peripheral blood-derived and alveolar macrophages stimulated with opsonized zymosan in vitro. This effect was abolished by prior treatment with an antibody specific for somatotropin. When either native or recombinant porcine somatotropin or native rat somatotropin was administered to hypophysectomized rats in vivo, activation of peritoneal macrophages, as measured by release of O2- in response to opsonized zymosan, was equivalent to that of macrophages from rats primed with the macrophage-activating factor interferon-gamma. Priming of macrophages in vivo was observed at physiologically relevant doses of somatotropin that caused a 10 to 40 percent increase in growth rate. Priming of mononuclear phagocytes for augmented production of reactive oxygen metabolites is a newly defined property of somatotropin.

Hypophysectomy inhibits the synthesis of tumor necrosis factor alpha by rat macrophages: partial restoration by exogenous growth hormone or interferon gamma.

We recently demonstrated that GH and interferon-gamma (IFN gamma) act in a similar manner to prime macrophages in vitro and in vivo for enhanced superoxide anion release. In this report we investigated the physiological role of the pituitary gland and GH in in vivo priming of resident peritoneal macrophages for the synthesis of tumor necrosis factor-alpha (TNF alpha) in vitro. Compared to normal rats, hypophysectomized animals had an 83% reduction in macrophage production of TNF alpha after in vitro stimulation with lipopolysaccharide. Sham operation had no significant effect on the ability of macrophages to secrete TNF alpha in response to lipopolysaccharide. Both native pituitary-derived porcine GH (48 micrograms/rat.9 days) and native pituitary-derived rat GH (96 micrograms/rat.9 days) more than tripled the in vitro production of TNF alpha by macrophages from hypophysectomized rats (342 and 358 vs. 112 U/mg protein for placebo-treated rats, respectively). Each of these preparations of GH also increased growth more than 6-fold in hypophysectomized rats (32 and 30 g vs. 5 g in placebo controls). Heat inactivation of native pituitary-derived porcine GH significantly reduced its in vivo ability to augment both TNF alpha synthesis by macrophages and body growth. Recombinant rat IFN gamma (2000 U/rat.9 days) more than tripled the production of TNF alpha by macrophages from hypophysectomized rats (343 vs. 112 U/mg protein). In contrast to its in vivo effects, addition of GH in vitro to macrophages from hypophysectomized rats did not prime these cells for the synthesis of TNF alpha, indicating an indirect mechanism of action for GH. To further test the biological relevancy of GH with respect to synthesis of TNF alpha, hemorrhagic necrosis of TNF alpha-sensitive murine methyl-cholanthrene-induced tumors was assessed in pituitary-intact mice. Native porcine GH (133 micrograms/mouse.7 days) significantly augmented both the necrosis to tumor ratio and the hemorrhage to tumor ratio. These findings establish the physiological relevance of the pituitary gland and GH in the priming of macrophages for TNF alpha synthesis.

Behavioral effects of L-5-hydroxytryptophan after destruction of ascending serotonergic pathways in the rat: the role of catecholaminergic neurons.

Lesions in the medial forebrain bundle of the rat produced a 68 to 74% decrease in telencephalic serotonin (5-HT) and a 30 to 43% decrease in jump threshold. L-5-Hydroxytryptophan (L-5-HTP; 37.5 mg/kg) returned the 5-HT content and jump threshold of lesioned rats to normal levels. These effects of L-5-HTP were also observed after the inhibition of extracerebral decarboxylase activity with Ro 4-4602 (50 mg/kg). Pretreatment with 6-hydroxydopamine (6-OHDA), which selectively destroys catecholamine neurons, had no effect on the jump threshold of nonlesioned rats nor did it further change the 5-HT content or jump threshold of lesioned rats. Lesioned rats pretreated with 6-OHDA demonstrated an increase in 5-HT content after L-5-HTP; however, their jump threshold remained significantly lower than that of controls. This ability of 6-OHDA to block the behavioral effects of L-5-HTP in lesioned rats was also observed after Ro 4-4602. In rats given Ro 4-4602, the accumulation of 5-HT at 90 minutes after injection of L-5-HTP was significantly correlated (r = 0.98) with total monoamine content. Thus, 6-OHDA pretreatment significantly decreased the net accumulation of 5-HT from L-5-HTP in nonlesioned rats. These rats also demonstrated further decreases in norepinephrine and dopamine content after L-5-HTP. It was concluded that L-5-HTP can be decarboxylated to 5-HT in serotonergic and catecholaminergic neurons and that the behavioral effects of L-5-HTP in lesioned rats may be due to the formation of 5-HT in catecholaminergic neurons where it may act as a "false-transmitter."

Kinetic analysis of the accumulation of gamma-aminobutyric acid by particulate fractions of rat brain: comparison of the effects of nipecotic acid and cis-3-aminocyclohexane-1-carboxylic acid.

Kinetic analyses indicate that nipecotic acid and cis-3-aminocyclohexane-1-carboxylic acid (cis-3-ACHC) inhibit GABA accumulation by similar mechanisms of action. Both amino acids are competitive inhibitors of particulate GABA accumulation when GABA and the inhibitor are added simultaneously to tissue fractions. However, preincubating the tissue with either amino acid produces noncompetitive inhibition of GABA accumulation at low concentrations of inhibitor and mixed inhibition at higher concentrations. The possible roles of intrasynaptosomal mechanisms and of astroglia in producing these effects are discussed. The most notable difference between cis-3-ACHC and the other amino acid inhibitors of GABA accumulation, such as nipecotic acid, cis-4-OH-nipecotic acid, guvacine, beta-proline, homo-beta-proline, and 2,4-diaminobutyric acid (DABA), is that cis-3-ACHC is approximately 3.5 times more potent as an inhibitor following preincubation. Thus, while cis-3-ACHC does inhibit GABA transport, its major site of action in the synaptosome may be intracellular.

Behavioral correlates of serotonin depletion.

Depletion of telencephalic serotonin (5-HT) content by medical forebrain bundle lesions, which interrupt the ascending serotonergic pathways or by DL-p-chlorophenylalanine produces an increased sensitivity to pain as measured by the flinch-jump, stabilimetric, or hot-plate methods. Examination of the effects of a number of other lesions and drugs indicated that dopamine, norepinephrine and acetylcholine are not involved in pain sensitivity. Dosages of 75 mg/kg DL-5-hydroxytryptophan(5-HTP), 37.5 mg/kg L-5-HTP or 50 mg/kg Ro 4-4602 (NI-(DL-seryl)-N2-(2,3,4-trihydroxybenzyl)hydrazine) plus 37.5 mg/kg L-5-HTP administered to medical forebrain bundle lesioned rats returned both the telencephalic content of 5-HT and the pain threshold to normal values. Injection of 37.5 mg/kg of D-5-HTP or an equimolar dose of L-dopa had no effect on pain threshold. Normal animals display increased sensitivity to pain and decreased 5-HT contents in frontal pole, hippocampus, and amygdala during dark as compared to light hours. All three of these telencephalic areas are innervated by the ascending serotonergic pathways, and cells in these areas show inhibition of firing following the iontophoretic application of 5-HT. Taken together these data suggest that the serotonergic system normally acts to inhibit the effects of painful stimuli. A review of a variety of behavioral effects of 5-HT depletion including an enhanced response to lysergic acid diethylamide and amphetamine suggests that the ascending serotonergic system may have a general role in the inhibition of arousal, rather than a specific role with respect to various categories of behavior.

The pituitary gland is required for protection against lethal effects of Salmonella typhimurium.

One-half of pituitary-intact or sham-operated rats survive infection with 10(9) colony-forming units of Salmonella typhimurium, whereas rats without a pituitary gland all die within a few days. When the dose of S. typhimurium is reduced 600-fold, 15-25% of the hypophysectomized rats survive, and the survival rate is significantly enhanced by administration of tetracycline, recombinant interferon gamma (IFN-gamma), or recombinant growth hormone (GH). The protective effect of GH is abolished by heat inactivation or with an antibody to GH. Spleens from normal and hypophysectomized rats treated with tetracycline, IFN-gamma, or GH have 59-99% fewer bacteria 5 days after infection as compared to control rats. Peritoneal macrophages from hypophysectomized rats that are infected in vitro with S. typhimurium kill half as many extracellular bacteria as compared to pituitary-intact rats, and this bactericidal capacity is significantly augmented 75-95% by either GH or IFN-gamma. These data establish that the pituitary gland is essential for homeostasis during an infectious episode and that GH plays an important role in host resistance by augmenting the ability of macrophages to kill S. typhimurium.

Murine macrophage activation with resorcyclic acid lactones (RALs): comparison with diethylstilbestrol and 17 beta-estradiol.

Zearalane, a resorcyclic acid lactone (RAL) derivative, activates murine macrophages (M phi) in vivo and in vitro. Mouse M phi incubated in vitro with different concentrations of zearalane released superoxide anion (O2-) on stimulation with either opsonized zymosan (Op-zym), phorbol myristate acetate (PMA), or Salmonella typhimurium. The levels of O2- released were similar to those released from M phi incubated in vitro with supernatants enriched in macrophage-activating factors from concanavalin A-stimulated mouse spleen cells. In contrast, 17 beta-estradiol (E2) or diethylstilbestrol (DES) induced little or no enhancement of O2- release. Zearalane, dideoxyzearalane, DES and E2 were tested for induction of host resistance to S. typhimurium infection in mice. Treatment of mice with zearalane (9 mg/kg) resulted in at least 65% survival 4 days post-infection, compared to 10% survival of mice with vehicle alone, DES, or E2. Peritoneal and alveolar M phi from the zearalane-treated mice released up to six times as much O2- on stimulation with Op-zym as M phi from the other treatment groups. M phi activation was observed for up to 7 days after intraperitoneal or subcutaneous administration of zearalane in either aqueous or organic vehicles. These results suggest that zearalane may enhance resistance to infection by increasing bactericidal activity due to increased release of toxic oxygen radicals by M phi and mononuclear phagocytes. These effects differ from the immunosuppressive effects reported for DES and E2.

Novel inhibitors of gamma-aminobutyric acid (GABA) uptake: anticonvulsant actions in rats and mice.

SK&F 89976A [N-(4,4-diphenyl-3-butenyl)-nipecotic acid] and SK&F 100330A [N-(4,4-diphenyl-3-butenyl)-guvacine] represent a new series of potent, orally active inhibitors of gamma-aminobutyric acid (GABA) uptake. In vitro studies with synaptosome-rich (P2) fractions of rat brain indicated that these compounds were approximately 20 times more potent than the parent amino acids as inhibitors of [3H]GABA uptake. They did not inhibit [3H] muscimol binding at nanomolar concentrations. The present studies demonstrated that these compounds were also potent anticonvulsants when administered either orally or i.p. to rats. Both compounds attenuated the forelimb extensor component of bicuculline-induced convulsions, but had no effect on strychnine-induced convulsions, indicating that they were acting through a GABAergic mechanism in vivo. Two animal models which are known to be indicative of anticonvulsant efficacy in man are inhibition of maximal electroshock seizures (MES) and inhibition of pentylenetetrazol (PTZ) convulsions in either rats or mice. SK&F 89976A, SK&F 100330A and several related compounds were potent inhibitors of PTZ convulsions in rats. SK&F 100330A also inhibited MES convulsions in rats. In contrast, neither compound inhibited MES or electroshock seizure threshold in mice, and whereas both compounds inhibited the tonic phase of PTZ convulsions in approximately 50% of the mice tested, this inhibition was not dose-related. Thus, the rat appears to be a more suitable species for further testing of these compounds. These studies indicate that the family of compounds represented by SK&F 89976A and SK&F 100330A may have clinically relevant anticonvulsant activity.

The macrophage-activating properties of growth hormone.

1. We compared the ability of growth hormone (GH) and a well-characterized macrophage-activating factor, interferon-gamma (IFN-gamma) to activate highly purified populations of alveolar macrophages. Both GH and IFN-gamma primed macrophages triggered with opsonized zymosan to secrete superoxide anion (O2-) in vitro, but IFN-gamma was effective at a 40-fold lower concentration. Antibody blocking studies demonstrated that the priming activity of GH was independent of IFN-gamma, and the activity of IFN-gamma was distinct from that of GH. 2. Both IFN-gamma and GH increased the capability of macrophages to kill Pasteurella multocida in vitro. 3. Hypophysectomized rats challenged with Salmonella typhimurium were significantly protected by injections of either GH or recombinant rat IFN-gamma in vivo compared to vehicle-treated controls, and the protective effect of GH was increased by incorporation into liposomes. 4. Insulin-like growth factor-I (IGF-I) also primed alveolar macrophages in vitro, which is consistent with the idea that the protective effects of GH in vivo might be mediated by augmenting the synthesis of IGF-I. These data support the concept of reciprocal systems of communication between the neuroendocrine and immune systems.

In vivo administration of recombinant growth hormone or gamma interferon activities macrophages: enhanced resistance to experimental Salmonella typhimurium infection is correlated with generation of reactive oxygen intermediates.

Purified and recombinant forms of growth hormone (GH) as well as of recombinant rat gamma interferon (IFN-gamma) enhance the survival of rats deprived of endogenous pituitary GH secretion by hypophysectomy (HX rats) and infected with virulent Salmonella typhimurium. Macrophages obtained from rats with intact pituitaries (pituitary-intact rats) or HX rats that were treated in vivo with either GH or the closely related hormone prolactin released elevated (P less than 0.05) levels of superoxide anion (O2-) after in vitro opsonized-zymosan stimulation compared with those from placebo-treated animals. These levels of O2- release were similar in magnitude to those of macrophages from rats treated in vivo with IFN-gamma. In time course in vivo macrophage activation studies, both IFN-gamma and GH significantly increased O2- secretion within 24 h, with maximal secretion occurring at day 3. Macrophages obtained from pituitary-intact and HX rats injected in vivo with GH also released elevated (P less than 0.05) levels of hydrogen peroxide (H2O2) and displayed enhanced (P less than 0.01) phagocytic activity toward opsonized Listeria monocytogenes in vitro. The mechanism of action of GH in vivo is likely to be a direct one because resident peritoneal macrophages from rats could be primed in vitro for enhanced secretion of O2- following triggering of these cells with opsonized zymosan. These data show that in vivo administration of two closely related pituitary hormones, GH and prolactin, can effectively prime macrophages, which is consistent with the hypothesis that GH mediates resistance to S. typhimurium by a direct stimulatory action on macrophages.