Siegel, Steven J
Email Address
ORCID
Disciplines
Search Results
Now showing 1 - 5 of 5
Publication Controlling the In Vitro Release Profiles for a System of Haloperidol-Loaded PLGA(2007-06-11) Siegel, Steven J; Budhian, Avinash; Winey, Karen IWe have used a systematic methodology to tailor the in vitro drug release profiles for a system of PLGA/PLA nanoparticles encapsulating a hydrophobic drug, haloperidol. We applied our previously developed sonication and homogenization methods to produce haloperidol-loaded PLGA/PLA nanoparticles with 200–1000 nm diameters and 0.2–2.5% drug content. The three important properties affecting release behavior were identified as: polymer hydrophobicity, particle size and particle coating. Increasing the polymer hydrophobicity reduces the initial burst and extends the period of release. Increasing the particle size reduces the initial burst and increases the rate of release. It was also shown that coating the particles with chitosan significantly reduces the initial burst without affecting other parts of the release profile. Various combinations of the above three properties were used to achieve in vitro release of drug over a period of 8, 25 and >40 days, with initial burst <25% and a steady release rate over the entire period of release. Polymer molecular weight and particle drug content were inconsequential for drug release in this system. Experimental in vitro drug release data were fitted with available mathematical models in literature to establish that the mechanism of drug release is predominantly diffusion controlled. The average value of drug diffusivities for PLGA and PLA nanoparticles was calculated and its variation with particle size was established.Publication Ketamine Modulates Theta and Gamma Oscillations(2009-01-01) Lazarewicz, Maciej T.; Ehrilichman, Richard S.; Gandal, Michael J.; Maxwell, Christina R.; Siegel, Steven J.; Finkel, Leif H.Ketamine, an N-methyl-D-aspartate (NMDA) receptor glutamatergic antagonist, has been studied as a model of schizophrenia when applied in subanesthetic doses. In EEG studies, ketamine affects sensory gating and alters the oscillatory characteristics of neuronal signals in a complexmanner. We investigated the effects of ketamine on in vivo recordings from the CA3 region of mouse hippocampus referenced to the ipsilateral frontal sinus using a paired-click auditory gating paradigm. One issue of particular interest was elucidating the effect of ketamine on background network activity, poststimulus evoked and induced activity. We find that ketamine attenuates the theta frequency band in both background activity and in poststimulus evoked activity. Ketamine also disrupts a late, poststimulus theta power reduction seen in control recordings. In the gamma frequency range, ketamine enhances both background and evoked power, but decreases relative induced power. These findings support a role for NMDA receptors in mediating the balance between theta and gamma responses to sensory stimuli, with possible implications for dysfunction in schizophrenia.Publication mGluR5-Antagonist Mediated Reversal of Elevated Stereotyped, Repetitive Behaviors in the VPA Model of Autism(2011-10-07) Mehta, Mili V; Gandal, Michael J.; Siegel, Steven JAutism spectrum disorders (ASD) are highly disabling developmental disorders with a population prevalence of 1–3%. Despite a strong genetic etiology, there are no current therapeutic options that target the core symptoms of ASD. Emerging evidence suggests that dysfunction of glutamatergic signaling, in particular through metabotropic glutamate receptor 5 (mGluR5) receptors, may contribute to phenotypic deficits and may be appropriate targets for pharmacologic intervention. This study assessed the therapeutic potential of 2-methyl-6-phenylethyl-pyrididine (MPEP), an mGluR5-receptor antagonist, on repetitive and anxiety-like behaviors in the valproic acid (VPA) mouse model of autism. Mice were exposed prenatally on day E13 to VPA and assessed for repetitive self-grooming and marble burying behaviors as adults. Anxiety-like behavior and locomotor activity were measured in an open-field. VPA-exposed mice displayed increased repetitive and anxiety-like behaviors, consistent with previously published results. Across both marble burying and self-grooming assays, MPEP significantly reduced repetitive behaviors in VPA-treated mice, but had no effect on locomotor activity. These results are consistent with emerging preclinical literature that mGluR5-antagonists may have therapeutic efficacy for core symptoms of autism.Publication Pharmacokinetic and behavioral characterization of a longterm antipsychotic delivery system in rodents and rabbits(2007-02-01) Metzger, Kayla L; Shoemaker, Jody M; Kahn, Jonathan B; Maxwell, Christina R; Liang, Yuling; Tokarczyk, Jan; Kanes, Stephen J; Hans, Meredith; Lowman, Anthony M; Winey, Karen I; Dan, Nily; Siegel, Steven J; Swerdlow, Neal RRationale: Non-adherence with medication remains the major correctable cause of poor outcome in schizophrenia. However, few treatments have addressed this major determinant of outcome with novel long-term delivery systems. Objectives: The aim of this study was to provide biological proof of concept for a long-term implantable antipsychotic delivery system in rodents and rabbits. Materials and methods: Implantable formulations of haloperidol were created using biodegradable polymers. Implants were characterized for in vitro release and in vivo behavior using prepulse inhibition of startle in rats and mice, as well as pharmacokinetics in rabbits. Results: Behavioral measures demonstrate the effectiveness of haloperidol implants delivering 1 mg/kg in mice and 0.6 mg/kg in rats to block amphetamine (10 mg/kg) in mice or apomorphine (0.5 mg/kg) in rats. Additionally, we demonstrate the pattern of release from single polymer implants for 1 year in rabbits. Conclusions: The current study suggests that implantable formulations are a viable approach to providing long-term delivery of antipsychotic medications in vivo using animal models of behavior and pharmacokinetics. In contrast to depot formulations, implantable formulations could last 6 months or longer. Additionally, implants can be removed throughout the delivery interval, offering a degree of reversibility not available with depot formulations.Publication Production of haloperidol loaded PLGA nanoparticles for extended controlled drug release of haloperidol(2005-11-01) Winey, Karen I; Budhian, Avinash; Siegel, Steven JThis study developed an emulsion-solvent evaporation method for producing haloperidol-loaded PLGA nanoparticles with up to 2% (wt/wt. of polymer) drug content, in vitro release duration of over 13 days and less than 20% burst release. The free haloperidol is removed from the nanoparticle suspension using a novel solid phase extraction technique. This leads to a more accurate determination of drug incorporation efficiency than the typical washing methods. It was discovered that PLGA end groups have a strong influence on haloperidol incorporation efficiency and its release from PLGA nanoparticles. The hydroxyl-terminated PLGA (uncapped) nanoparticles have a drug incorporation efficiency of more than 30% as compared to only 10% with methyl-terminated PLGA (capped) nanoparticles. The in vitro release profile of nanoparticles with uncapped PLGA has a longer release period and a lower initial burst as compared to capped PLGA. By varying other processing and materials parameters, the size, haloperidol incorporation and haloperidol release of the haloperidol-loaded PLGA nanoparticles were controlled.