Preparation and evaluation of a sustained morphine delivery system in rats

Review of novel particulate antigen delivery systems with special focus on treatment of type I allergy

For the treatment of infectious diseases, cancer and allergy, the directed induction of an appropriate immune response is the ultimate goal. Therefore, with the development of pure, often very small proteins, peptides or DNA by molecular biology techniques, the research for suitable adjuvants or delivery systems became increasingly important. Particle formulations are made of a variety of materials, including lipids, proteins or amino acids, polysaccharides, polyacrylic substances or organic acids. Microparticles serve as vehicles and provide a depot for the entrapped or coupled antigen. The release occurs in a pulsatile or continuous manner, a feature, which is well controllable for many particulate systems. Particles attract antigen presenting cells to the administration site, thereby guaranteeing the efficient presentation of the antigen to the immune system. Importantly, particles also protect the entrapped substance. This is especially necessary after oral application to avoid gastric or tryptic breakdown. In this article, the design and construction of different antigen delivery systems and their immune effects, with special focus on the suitability for allergy treatment, are discussed.

The effects of acute and chronic morphine on regional distribution of cardiac output in brain

Both acute and chronic administration of morphine resulted in an increase in the percent cardiac output received by brain. However, various brain regions were affected differently by the drug treatments. The greatest increases in percent cardiac output received after chronic administration of morphine occurred in pons and cerebellum, while the greatest increases after acute administration occurred in cortex and midbrain. The changes found are in contrast with earlier studies which suggest that morphine has no effect on cerebral blood flow.

The effects of organophosphate-induced cholinergic stimulation on the antibody response to sheep erythrocytes in inbred mice

In a previous study, we demonstrated that parathion suppressed both the primary IgM and IgG response to sheep erythrocytes (SRC) in inbred and outbred mice (G. P. Casale, S. D. Cohen, and R. A. DiCapua, 1982, toxicologist 2, 94). Suppression occurred after a dosage which produced cholinergic effects but was absent after a lower dosage which did not produce cholinergic signs. This information suggested that immunosuppression might be mediated indirectly as a result of toxic chemical stress. The present study evaluated the relationship between the anticholinesterase action of parathion, malathion, and dichlorvos (DDVP) and their effects on the primary humoral response to SRC. Male C57Bl/6 mice were given a single dose of parathion (16 mg/kg, po), malathion (720 mg/kg, po), or DDVP (120 mg/kg, po) 2 days after immunization with SRC. Two days later, tissues were removed for cholinesterase (CHE) assay and enumeration of splenic antibody-forming cells (PFC). All three compounds produced moderate to severe cholinergic poisoning. DDVP produced cholinergic signs beginning 1/2 hr after dosing and lasting 1/2 to 1 hr. This profile was associated with a rapid but transient inhibition of brain CHE activity. In contrast, malathion and parathion produced prolonged cholinergic poisoning (4 to 7 hr) and prolonged suppression of brain CHE activity. All three compounds suppressed the primary IgM response. However, when they were given as multiple lower doses, none of the compounds suppressed the primary IgG response. These latter treatments produced no cholinergic signs. The cholinomimetic agent, arecoline (65 mg/kg, ip) produced a short-lived cholinergic crisis but no IgM suppression. Sustained-release arecoline produced prolonged cholinergic poisoning (3 to 5 hr) and reduced the number of IgM PFC to 50% of control. These results demonstrated that organophosphate-induced immunosuppression was associated with severe cholinergic stimulation. The immunosuppression may result from direct action of acetylcholine upon the immune system or it may be secondary to the toxic chemical stress associated with cholinergic poisoning.

Cyclo(Leu-Gly) attenuates the striatal dopaminergic supersensitivity induced by chronic morphine: agonist binding to D2 dopamine receptors correlates with stereotypic behavior

We have previously shown that MIF and its structural analog, cyclo-(Leu-Gly), block analgesic tolerance and some signs of physical dependence following chronic opiate administration. The mechanism of action of these peptides has not been clearly elucidated. The data presented here suggests that chronic opiate administration causes a behavioral supersensitivity to dopamine (DA) agonists which is highly correlated with an increase in D2-Hi receptor affinity for DA agonists, but not antagonists. Both the behavioral and receptor changes are blocked by prior administration of cyclo(Leu-Gly). This suggests that the ability of cyclo(Leu-Gly) to block the development of opiate addictive states may involve DA synaptic elements.

Peptide inhibition of morphine-induced dopaminergic supersensitivity

Injection of the peptide cyclo(Leu-Gly) into rats prior to chronic exposure to morphine, inhibits: 1) the development of analgesic tolerance; 2) some signs of physical dependence; and, 3) morphine-induced increases in behavioral responses to dopamine agonists. Although there was no change in the total number of high affinity striatal dopamine receptors, chronic morphine treatment did increase the affinity of the ligand at the receptor. The peptide blocked not only the affinity change, but the increased behavioral response to apomorphine as well. These behavioral changes correlate significantly with the neurochemical changes in dopamine receptors following chronic morphine treatment. Therefore, some of the pharmacological efforts of morphine may be mediated by changes in CNS dopamine receptors and that the peptides may act by inhibiting these neurochemical changes.

Changes in locomotor response to beta-endorphin microinfusion during and after opiate abstinence syndrome--a proposal for a model of the onset of mania

Beta-Endorphin (0.3 or 0.6 nanomoles) was infused into the A10-ventral tegmental area (VTA) of male Wistar rats previously treated for 6 days with either morphine sulfate or lactose via subcutaneously implanted silastic pellets. Beta-Endorphin microinfusions occurred at 24 and 96 hours after pellets were removed. Profound changes in locomotor response to beta-endorphin were found, with morphine-pretreated rats showing a spontaneous switch from hyporesponsiveness to hyperresponsiveness over 72 hours, compared to lactose-pretreated controls. These findings may reflect on current biochemical theories regarding the "switch" process in bipolar affective disease. The data can be viewed within a heuristic model of receptor changes which may underlie the transition from depression to mania.

A new subcutaneously-implantable reservoir for sustained release of nicotine in the rat

A subcutaneously-implantable reservoir for the sustained release of nicotine is described. The device, dubbed INR for Implantable Nicotine Reservoir, is a small glass cup sealed with Silastic polymer. It releases 3.4 mg of nicotine per 24 hours. When implanted into moderately-sized female Sprague-Dawley rats it produces blood nicotine levels of 400-500 ng/ml which remain relatively stable over at least 18 days. INRs are nontoxic, reproducible, inexpensive, and adaptable for pharmacological and toxicological studies in rats and other small animals.

Polydimethylsiloxane pellets for sustained delivery of morphine in mice

A new dosage form was designed whereby a polymeric silicone elastomer provided sustained delivery of morphine to mice over 11 days. These pellets, which can be made easily and inexpensively with a standard tablet mold, gradually released morphine sulfate into the implanted mice. Maximal morphine-induced physical dependence, measured by jumping during naloxone-induced withdrawal, was observed 3--5 days after implantation. At this time, slightly less than 50% of the morphine sulfate had been released. Drug release continued through Day 11 and was accompanied by a physical dependence of decreased magnitude compared to that observed on Day 3 or 5.

Dependence in rats after one injection of heroin-, LAAM- or hydromorphone-zinc tannate

Complex zinc tannate salts of heroin, hydromorphone and l-alpha-acetylmethadol were synthesized and injected in a slow-release vehicle, into rats. One, 3, 7, 10 and 14 days after the drug was administered rats were injected with naloxone hydrochloride (10 mg/kg) and during the following 4 hours body weights, core temperature and behavioral signs such as diarrhea, writhing, teeth chattering and wet dog shakes were recorded. On every naloxone testing day the narcotic-treated groups presented behavioral signs of abstinence, but weight loss and temperature changes were much less consistent. Reduction of core temperature following naloxone administration seems to be an earlier indicator of physical dependence than weight loss. According to the parameters tested a level of physical dependence can persist for at least two weeks after a single injection of these narcotic salts.

Effect of water-soluble carriers on morphine sulfate release from a silicone polymer

The influence of gelatin, sodium lauryl sulfate, lactose, and sodium alginate on morphine sulfate diffusion from cylindrical silicone polymer pellets was examined in isotonic pH 7.4 phosphate buffer. These water-soluble carriers caused the pellets to swell in aqueous media. Sodium alginate exerted the greatest influence on drug release. The morphine sulfate diffusion rate from the cylindrical pellets increased as the matrix alginate content increased up to 20%. Water-soluble carrier incorporation into silicone polymeric matrixes permits controlled release of water-soluble drugs that otherwise would be released extremely slowly from the polymer. Drug diffusion from the silicone matrix containing sodium alginate followed second-order kinetics. The release mechanism probably involves the creation of pores or pathways through the matrix secondary to the swelling.