Effects of opiate receptor drugs injected intracerebrally into the normovolemic and hypovolemic monkey

Systemic injection of naloxone (NAL), an opioid-receptor antagonist, significantly elevates systolic blood pressure (SBP) in anesthetized hypovolemic monkeys, providing indirect evidence that endogenous opioids contribute to cardiovascular depression during shock. The purpose of this study was to identify specific centrally located opioid receptor sites that participate in SBP regulation under normovolemic and hypovolemic conditions. In 6 monkeys, bilateral guide cannulae were stereotaxically implanted above areas ranging from the diencephalon to the lower medulla. Microinjections (1 μl) of D- Ala²-Met-enkephalinamide (DAME) (3.4–27.2 nM) into normovolemic unanesthetized monkeys reduced SBP by 10–65 mm Hg in a dose-related fashion. Subsequent injection of NAL (12.2 nM) attenuated this hypotensive response. Heart rate fell 20–40 bpm with DAME, but not in response to dose. In the anesthetized animal rendered hypotensive (SBP=45 mm Hg) by hemorrhage, NAL injected into predetermined DAME-sensitive sites failed to increase SBP more than 5 mm Hg. Even consecutive injections into multiple sites elevated SBP only 20 mm Hg. We conclude that the centrally located opioid-sensitive sites tested exert only a mild influence in mediating hemorrhagic hypotension.     

Metabolism of intracerebrally injected mevalonate in brain of suckling and young adult rats

We have investigated the in vivo metabolism via sterol and nonsterol pathways of intracerebrally injected mevalonate (MVA) in brains from suckling (10-day-old) and young adult (60-day-old) rats. Results of our study indicated that increasing the amounts of MVA injected increased MVA incorporation into all the lipid fractions examined. The incorporation of MVA into nonsaponiable lipids (NSF) and digitonin precipitable sterols (DPS) was similar in brains from adult and suckling rats. In brain tissue from both suckling and young adult rats the synthesis of dolichol from MVA varied with the amounts of MVA injected. Significant amounts of MVA were recovered in phosphorylated and free polyprenols (farnesol and geraniol) in brain tissue from rats of both ages. Also in both groups of animals, the amounts of MVA incorporated in phosphorylated and free farnesol were higher than the amounts recovered in either, phosphorylated or free geraniol. The amounts of MVA incorporated into the prenoic/fatty acid fraction by brain tissue from both suckling and young adult rats were less than 1% of the total MVA incorporated (nonsaponifiable and saponifiable lipids). Incorporation of MVA into the prenoic/fatty acid fraction by brain tissue was higher in suckling than in young adult rats. These data indicate that the brain tissue from suckling and young adult rats do not differ in their capacity to metabolize MVA into squalene and sterols and that in brain, metabolism of MVA by a shunt pathway is minimal. This suggests that in vivo regulation of cholesterol synthesis during brain development must occur at a step(s) in the sterol synthetic pathway prior to mevalonate, and that metabolism of mevalonate by shunt pathway did not play a role in the developmental regulation of brain sterol synthesis. The data also suggest that in both groups of animals the synthesis of squalene by synthetase may in part control brain sterol synthesis and the synthesis of dolichol is regulated by MVA concentration in the tissue.     

Action of selected serotonin antagonists on hyperthermia evoked by intracerebrally injected beta-endorphin

Methergoline, an antagonist of cerebral serotonin receptors, has been shown to significantly reduce the rise in rectal temperature (Tre) produced by the intracerebral microinjection of beta-endorphin. In this study the role of serotonin in the increase in Tre elicited by beta-endorphin was further examined using three additional serotonin antagonists. beta-Endorphin was administered twice to rats using a crossover design in which half of the animals were first pretreated with the vehicle solution and half with the antagonist. Serotonin antagonists used were: methergoline, methysergide, cinanserin and cyproheptadine. Although methergoline did cause a marked reduction in the beta-endorphin-induced rise in Tre, neither methysergide, nor cinanserin, nor cyproheptadine produced a marked reduction in the hyperthermia. Since methergoline also interacts with the dopamine receptor, the effect of a dopamine antagonist, haloperidol, on the endorphin-evoked response was also examined. Haloperidol failed to attenuate the rise in Tre. The reason for the apparent discrepancy in the action of these serotonin antagonists is unclear. Further research may reveal distinct subpopulations of serotonin receptors at which these antagonists exert differential effects.     

Behavior of certain fungi injected in a mixed suspension into mice

Summary A total of 40 mice was injected with mixed suspensions ofC. albicans, C. neoformans, B. dermatitidis andH. capsulatum intraperitoneally, subcutaneously, intravenously and intracerebrally. Cultures from spleen, liver, kidney, lung and brain were made at intervals of 1, 4, 8, 15 and 30 days after inoculation. Results were recorded and compared with those obtained from a similar experiment where the organisms were injected separately.This project was aided in part by grant E-986 of the N.I.H.     

A combined histochemical-neurophysiological technique for investigating the extent of diffusion of intracerebrally injected drugs

In order to 'dissect out' the function of a given region of the brain, the local application of a chemical transmitter probably parallels closely what is actually occurring biologically at the local site. This paper addresses itself to the problem of diffusion of drugs and describes the application of a modern device (the osmotic minipump) which produces a constant flow of minute quantities of the agent into the brain structure. Neurophysiological, behavioural, and histochemical investigations have been carried out in different species. Although the histochemical results of the minipump experiments indicate some spread, yet this seems to be at a concentration which would have no apparent pharmacological action. This was confirmed by our neurophysiological and behavioural studies and also by some recent reports in the literature.     

Psychotropic drugs and the metabolism of intracerebrally injected tryptamine, 5-hydroxytryptamine, and norepinephrine

Abstract— Rats were injected intracerebrally with labelled tryptamine, 5-hydroxytrypt-amine (5-HT) and norepinephrine (NE). The disappearance of the amines and their metabolites as a function of time was determined. Tryptamine disappeared very rapidly, with a half-life of 5 min in normal animals and of 45 min in rats treated with a monoamine oxidase (MAO) inhibitor. The level of radioactive 5-HT declined in two phases, with half-lives of 45 min and 3 h respectively. The 5-hydroxyindoleacetic acid (5-HIAA) that was formed disappeared with a half-life of approximately 1 h. After inhibition of monoamine oxidase, there was only a single phase of 5-HT disappearance (half-life of 4 h). Reserpine decreased and imipramine increased the amount of 5-HT remaining 4 h after injection. Of the NE injected, 12 per cent was converted to methoxyhydroxyphenylglycol sulphate (MHPGS), which disappeared with a half life of 3 h. Reserpine doubled the amount of methoxyhydroxyphenylglycol sulfate formed, but did not alter its rate of disappearance, its peak concentration occurring about 30 min after injection of NE in both control and reserpine-treated rats.     

The effect of hyperbaric oxygenation on the viability of human fat injected into nude mice

Autologous free-fat injection for the correction of soft-tissue defects has become a common procedure in plastic surgery. The main shortcoming of this method for achieving permanent soft-tissue augmentation is the partial absorption of the injected fat, an occurrence that leads to the need for both overcorrection and repeated fat reinjection. Improving the oxygenation of the injected fat has been suggested as a means of helping to overcome the initial critical phase that occurs postinjection (when the fat cells are nourished by osmosis), increasing phagocyte activity, accelerating fibroblast activity and collagen formation, and enhancing angiogenesis. In addition, the hyperbaric oxygen-mediated decrement in endothelial leukocyte adhesion will decrease cytokine release, thereby reducing edema and inflammatory responses. The purpose of the present study was to examine the effect of hyperbaric oxygenation on improving the viability of injected fat. Adipose tissue obtained from human breasts by suction-assisted lipectomy was injected into the subcuticular nuchal region in nude mice. The mice were then exposed to daily hyperbaric oxygen treatments, breathing 100% oxygen at 2 atmospheres absolute (ATA) for 90 minutes. The duration of the administered hyperbaric oxygen therapy was 5, 10, or 15 days, according to the study group. Mice exposed to normobaric air alone served as the control group, and each group included 10 animals. The rats were killed 15 weeks after fat injection. The grafts were dissected out, weight and volume were measured, and histologic evaluation was performed. In all of the study groups, at least part of the injected fat survived, giving the desired clinical outcome. No significant differences could be found between the groups regarding fat weight and volume. Histopathologic examination of the dissected grafts demonstrated a significantly better integrity of the fat tissue in the group that received hyperbaric oxygen for 5 days (p = 0.047). This finding was manifested by the presence of well-organized, intact fat cells, along with a normal appearance of the fibrous septa and blood vessels. The worst results were found in animals treated by hyperbaric oxygenation for 15 consecutive days. An inverse correlation was found between an increased dose of the high-pressure oxygen and fat tissue integrity (r = -0.87, p = 0.076). The toxic effects of highly reactive oxygen species on fat cells might explain the failure of an excessively high dose of hyperbaric oxygen to provide any beneficial outcome. The clinical relevance of these results should be further investigated.     

Metabolism of intracerebrally administered histidine, histamine and imidazoleacetic acid in mice and frogs

Abstract— After intracerebral administration of [¹⁴C]histidine to mice the major labelled substance found in the brain extracts was histidine itself; small amounts of labelled carnosine and homocarnosine were detected. No other labelled substances were detected on radio- autographs of two-dimensional TLC's of the extracts. In the case of the frog, radioactive histidine, N-acetylhistidine, carnosine and homocarnosine were found in the brain extracts at various times after intracerebral injection of the labelled histidine. With time, approximately 90 per cent of the radioactivity in the extracts was found in the N-acetylhistidine. In neither the mouse nor frog could we find unequivocal evidence for the formation either of histamine or imidazoleacetic acid from intracerebrally administered histidine, but our analytical procedures may have lacked sufficient sensitivity to pick up extremely low activities of histamine and imidazoleacetic acid. Experiments with [¹⁴C]histamine administered intracerebrally into mice demonstrated the major pathway of metabolism in brain to be histamine → methylhistamine → methylimidazoleacetic acid. No detectable label appeared in inlidazoleacetic acid. In the frog intracerebral administration of the labelled histamine led to the formation of methylhistamine and imidazoleacetic acid, but at most only traces of methylimidazoleacetic acid were found. The injection of [¹⁴C]imidazoleacetic acid intra- cerebrally into mice and frogs resulted in virtually no loss of the label in the form administered in the frog brain over a period of 4 h and in a slow rate of decrease in the mouse brain. No radioactive metabolites of imidazoleacetic acid were found in either species. The limitations of trying to determine natural functions of substances in brain by following the fate of exogenously administered materials is discussed.     

The effect of ascorbic acid on the amine-nitrite and nitrosamine mutagenicity in bacteria injected into mice

Ascorbic acid was tested for its ability to increase or decrease the induction of bacterial mutations by dimethylnitrosamine (DMN) or aminopyrine plus nitrite within intact mice. No evidence was found of the mutagenicity of ascorbic acid itself when tested alone or in the presence of copper ions. Similarly, no increase or decrease in the DMN-induced mutation frequency was observed. However, ascorbic acid was found to decrease the aminopyrine/ nitrite-induced mutation frequency to an extent which was dependent on the experimental conditions used.     

Duffy blood group and hemoglobin variants

Summary Data on a sample of 809 Afro-Americans indicated that there is no association between Duffy null (a^-, b^-) blood type and sickle cell trait. The results further rule out close linkage as an alternative hypothesis to explain the reported association between these loci in areas where falciparum and vivax malaria are endemic and indicate that, even if the two loci are independent or loosely linked, direct evidence of the selection favoring AS Fy^-Fy^- individuals must come from populations where mixed malaria infections occur. Stratification, as an explanation for the reported association, is also discussed.     

Haemoglobin variants in mice.

Haemoglobin variants were studied in wild and laboratory house mice (Mus musculus), including standard and new inbred strains, using starch-gel electrophoretic technique. Single (Hbbs) or diffuse (Hbbd) types of haemoglobin were found in all of them. The embryonic haemoglobin pattern was different from although similar to that of the adult in all the strains. The haemoglobins revealed monomorphism in the inbred strains, while polymorphism was observed in non-inbred laboratory and wild mice.