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Jie Shen,1 Marina Bejanian2 1Department of Translational Sciences, 2Department of Ophthalmology Clinical Development, Allergan plc, Irvine, CA, USA Purpose: Many patients with glaucoma require combination therapies to achieve target intraocular pressure (IOP) and preserve visual function. Ocular hypotensives often contain a preservative (eg, benzalkonium chloride [BAK]), but preservative-free (PF) formulations have been developed for patients with sensitivity. A Phase III study found the efficacy of bimatoprost 0.03%/timolol 0.5% (bim/tim, Ganfort®) PF to be equivalent to that of preserved bim/tim, although a trend favoring bim/tim PF was observed. As BAK is a corneal penetration enhancer, this literature review aims to explain these findings by exploring the relationship between timolol concentration and its IOP-lowering effect. Methods: Systematic searches were performed in Scopus and PubMed for clinical trials published in English between 1960 and July 2014 using the keywords “timolol”, “intraocular pressure”, and the concentrations “1%, 0.5%, OR 0.25%”. Articles that directly compared IOP-lowering effects of ≥2 concentrations of timolol were identified by manual screening, and cross-checked for duplication. Results: Seventeen studies that included 10–371 patients were evaluated; the majority were randomized (16/17), double-masked (14/17), and enrolled patients with open-angle glaucoma or ocular hypertension (12/17). All studies investigated timolol in preserved formulations. Timolol concentrations tested ranged from 0.008% to 1.5%. Of 13 studies comparing timolol 0.25% versus 0.5%, two found the 0.25% dose to have greater IOP-lowering effects, and three reported the opposite; eight reported similar IOP lowering. Results also indicate that timolol 0.5% may be more effective than higher concentrations. Conclusion: The evidence suggests that timolol may have an inverted U-shaped dose–response curve, and that its optimal IOP-lowering concentration is between 0.25% and 0.5%. Compared with bim/tim, removal of the permeability enhancer BAK in bim/tim PF could have resulted in a lower timolol concentration at the target site, bringing the effective concentration within the 0.25%–0.5% range and enhancing the efficacy of bim/tim PF. Keywords: glaucoma, intraocular pressure, timolol, bimatoprost, preservative, dose–response

M Francesca Cordeiro,1 Ivan Goldberg,2 Rhett Schiffman,3 Paula Bernstein,3 Marina Bejanian31Western Eye Hospital, Imperial College Healthcare NHS Trust, London, UK; 2Discipline of Ophthalmology, University of Sydney, Sydney, NSW, Australia; 3Allergan, Inc., Irvine, CA, USAPurpose: To evaluate, using subgroup analysis, the effect of treatment status on the intraocular pressure (IOP)-lowering efficacy of a preservative-free formulation of fixed-combination bimatoprost 0.03%/timolol 0.5% (FCBT PF).Methods: A primary, multicenter, randomized, double-masked, 12-week study compared the efficacy and safety of FCBT PF with preserved FCBT (Ganfort®) in 561 patients diagnosed with glaucoma or ocular hypertension. For this analysis, eligible patients were treatment-naïve or had inadequate IOP lowering and underwent a washout of previous treatment. IOP (8 am, 10 am, and 4 pm) was measured at baseline and weeks 2, 6, and 12. Subgroup analysis of the FCBT PF arm assessed changes in average eye IOP from baseline in treatment-naïve vs previously treated patients. To evaluate the effect of treatment status at baseline (treatment-naïve vs previously treated) on IOP reduction in the FCBT PF treatment group, an analysis of covariance model was used with treatment status and investigator as fixed effects, and baseline average eye IOP, age, glaucoma diagnosis, and baseline average eye corneal thickness as covariates. P-values and the 95% confidence intervals were determined using the model.Results: In the FCBT PF arm, IOP mean changes from baseline ranged from -8.7 mmHg to -9.8 mmHg in treatment-naïve patients (N=50), compared with -7.3 mmHg to -8.5 mmHg in previously treated patients (N=228). Baseline IOP, age, glaucoma diagnosis, and corneal thickness significantly affected IOP reduction in the FCBT PF group. Adjusting for these covariates, FCBT PF had a greater IOP-lowering effect (0.8–1.7 mmHg) in treatment-naïve patients than previously treated patients, which was statistically significant (P≤0.05) at seven of nine time points.Conclusion: In this subgroup analysis, FCBT PF reduced IOP more effectively in treatment-naïve than in previously treated patients possibly due, in part, to altered responsiveness or tachyphylaxis that has been associated with prior ocular hypotensive agent treatment.Keywords: glaucoma, ocular hypertension, intraocular pressure, bimatoprost, timolol, benzalkonium chloride

Purpose: To evaluate the effects of a single bimatoprost implant administration on 24-hour intraocular pressure (IOP) lowering at 8 weeks, and 1-year IOP-lowering efficacy and safety outcomes., Design: Multicenter, open-label, 12-month, phase 3b study (NCT04285580)., Participants: Adults with open-angle glaucoma or ocular hypertension., Methods: Participants (n = 31) received 10-μg bimatoprost implant in the study eye on day 1; IOP (sitting and/or supine) was measured with pneumatonometry every 2 hours throughout a 24-hour period at baseline and week 8. IOP was measured by Goldmann applanation tonometry (GAT) at hour 0 (8 am ± 1 hour) at baseline, weeks 8 and 16, and months 6, 9, and 12., Main Outcome Measures: The primary endpoint was the week-8 hour-matched change from baseline in habitual position IOP over 24 hours assessed with pneumatonometry. Hour 0 IOP change from baseline measured with GAT in study eyes that received no additional (rescue) IOP-lowering treatment, treatment-emergent adverse events (TEAEs), and central corneal endothelial cell density (CECD) were evaluated through 12 months., Results: The mean (standard deviation [SD]) baseline IOP at hour 0 was 24.2 (2.70) mmHg and 25.3 (7.15) mmHg by GAT and pneumatonometry, respectively. Pneumatonometer measurements of IOP taken over 24 hours at week 8 with the participant in habitual position (sitting from 8 am to 10 pm, supine from 12 am to 6 am) showed consistent IOP lowering through the day and night and reduced fluctuation in IOP. The range in IOP measurements over 24 hours was reduced from baseline by a mean (SD) of -1.6 (2.98) mmHg. All 31 bimatoprost implant-treated participants completed the 12-month study; 23 (74%) required no rescue IOP-lowering treatment. The mean (SD) IOP reduction from baseline at month 12 in nonrescued eyes was -4.3 (3.35) mmHg. The most common TEAE was conjunctival hyperemia (incidence 35.5%, 11/31). No implant-treated eye had a ≥ 15% loss in CECD from baseline., Conclusions: A single intracameral administration of the bimatoprost implant lowered IOP in the habitual position consistently throughout the day and night at week 8. The majority of participants continued to have reduced IOP for 1 year without additional therapy. The 1-year safety profile was favorable., Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article., (Copyright © 2023 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the time course of biodegradation of an intracameral, biodegradable, sustained-release bimatoprost implant that lowers intraocular pressure without the need for daily eye drops. Methods: In 2 identically designed, randomized, phase 3 clinical trials, adults with open-angle glaucoma or ocular hypertension and open iridocorneal angles inferiorly in the study eye were administered 10- or 15-μg bimatoprost implant (day 1 and weeks 16 and 32) or twice-daily topical timolol 0.5%. Implants were assessed on gonioscopy throughout the studies. Investigators reported whether implants were visible, estimated the size of visible implants relative to their initial size at implantation, and reported the implant location. Data for 10-μg implant placed on day 1 were pooled from both studies for analysis. Results: A total of 372 patients received the 10-μg bimatoprost implant. The degree of implant biodegradation at each follow-up time point was variable among patients. The implant frequently swelled during the initial phase of biodegradation from 6 to 28 weeks. Accelerated biodegradation occurred between 31 and 52 weeks, resulting in 82% of implants absent or ≤25% of initial size by 52 weeks. By month 20, 95% of implants had biodegraded to absent or ≤25% of initial size. The implant was predominantly located inferiorly in the iridocorneal angle. Conclusions: Bimatoprost implant biodegradation in phase 3 studies showed some degree of variability among patients. Clinically significant implant biodegradation was observed in the majority of patients by 12 months. Clinical studies are in progress to further understand implant biodegradation and the ideal timing for implant re-administration. ClinicalTrials.gov NCT02247804; ClinicalTrials.gov NCT02250651.

Purpose: To evaluate the intraocular pressure (IOP)-lowering efficacy and safety of 10- and 15-μg bimatoprost implant in subjects with open-angle glaucoma (OAG) and ocular hypertension (OHT) after initial and repeated administrations., Design: Randomized, 20-month, multicenter, subject- and efficacy evaluator-masked, parallel-group, phase 3 clinical study., Participants: Adults with OAG or OHT in each eye, open iridocorneal angle inferiorly in the study eye, and study eye baseline IOP (hour 0; 8 am) of 22-32 mmHg after washout., Methods: Study eyes received bimatoprost implant 10 μg (n = 198) or 15 μg (n = 198) on day 1 with readministration at weeks 16 and 32, or twice-daily topical timolol maleate 0.5% (n = 198). Intraocular pressure was measured at hours 0 and 2 at each visit., Main Outcome Measures: Primary end points were IOP and change from baseline IOP through week 12. Safety measures included treatment-emergent adverse events (TEAEs) and corneal endothelial cell density (CECD)., Results: Both dose strengths of bimatoprost implant were noninferior to timolol in IOP lowering after each administration. Mean diurnal IOP was 24.0, 24.2, and 23.9 mmHg at baseline and from 16.5-17.2, 16.5-17.0, and 17.1-17.5 mmHg through week 12 in the 10-μg implant, 15-μg implant, and timolol groups, respectively. The incidence of corneal and inflammatory TEAEs of interest (e.g., corneal endothelial cell loss, iritis) was higher with bimatoprost implant than timolol and highest with the 15-μg dose strength. Incidence of corneal TEAEs increased after repeated treatment; with 3 administrations at fixed 16-week intervals, incidence of ≥20% CECD loss was 10.2% (10-μg implant) and 21.8% (15-μg implant). Mean best-corrected visual acuity (BCVA) was stable; 3 implant-treated subjects with corneal TEAEs had >2-line BCVA loss at their last visit., Conclusions: Both dose strengths of bimatoprost implant met the primary end point of noninferiority to timolol through week 12. One year after 3 administrations, IOP was controlled in most subjects without additional treatment. The risk-benefit assessment favored the 10-μg implant over the 15-μg implant. Ongoing studies are evaluating other administration regimens to reduce the potential for CECD loss. The bimatoprost implant has potential to improve adherence and reduce treatment burden in glaucoma., (Copyright © 2020 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Objective: The objective of this study was to evaluate the safety and intraocular pressure (IOP)-lowering effects over 24 months of biodegradable bimatoprost sustained-release implant (Bimatoprost SR) administration versus topical bimatoprost 0.03% in patients with open-angle glaucoma (OAG)., Methods: This was a phase I/II, prospective, 24-month, dose-ranging, paired-eye controlled clinical trial. At baseline following washout, adult patients with OAG (N = 75) received Bimatoprost SR (6, 10, 15, or 20 µg) intracamerally in the study eye; the fellow eye received topical bimatoprost 0.03% once daily. Rescue topical IOP-lowering medication or single repeat administration with implant was permitted. The primary endpoint was IOP change from baseline. Safety measures included adverse events (AEs)., Results: At month 24, mean IOP reduction from baseline was 7.5, 7.3, 7.3, and 8.9 mmHg in eyes treated with Bimatoprost SR 6, 10, 15, and 20 µg, respectively, versus 8.2 mmHg in pooled fellow eyes; 68, 40, and 28% of pooled study eyes had not been rescued/retreated at months 6, 12, and 24, respectively. AEs in study eyes that occurred ≤ 2 days post-procedure typically were transient. After 2 days post-procedure, overall AE incidence was similar between study and fellow eyes, with some events typically associated with topical prostaglandin analogs having lower incidence in study eyes., Conclusions: Bimatoprost SR showed favorable efficacy and safety profiles up to 24 months, with all evaluated dose strengths demonstrating overall IOP-reducing effects comparable to those of topical bimatoprost. Targeted and sustained delivery of bimatoprost resulted in protracted IOP lowering, suggesting that Bimatoprost SR may represent a transformational new approach to glaucoma therapy. Clinicaltrials.gov identifier: NCT01157364.

Purpose: To explore the ocular distribution of bimatoprost after intracameral administration of a biodegradable sustained-release bimatoprost implant (Bimatoprost SR) versus repeated topical administration of bimatoprost 0.03% ophthalmic solution in dogs. Bimatoprost SR and topical bimatoprost 0.03% previously were shown to have similar intraocular pressure-lowering effects in humans in a phase 1/2 clinical trial., Methods: Twenty-four beagle dogs received either once-daily topical bimatoprost 0.03% for 7 days or a bilateral intracameral administration of Bimatoprost SR (15 μg). At predetermined time points, ocular tissues were collected and concentrations of bimatoprost and bimatoprost acid were quantified using liquid chromatography-tandem mass spectrometry., Results: Bimatoprost SR administration enhanced delivery of study drug to a site of action [iris-ciliary body (ICB)] compared with topical bimatoprost (C max [bimatoprost+bimatoprost acid] = 18,200 and 4.13 ng/g, respectively). However, distribution of drug to tissues associated with prostaglandin analog (PGA)-related side effects (i.e., bulbar conjunctiva, eyelid margins, and periorbital fat) was limited following Bimatoprost SR administration (C max [bimatoprost+bimatoprost acid] = BLQ [beneath the limit of quantitation] to 0.354 ng/g) compared with topical dosing (C max [bimatoprost+bimatoprost acid] = 36.6-2,110 ng/g)., Conclusions: Bimatoprost SR administration in dogs selectively delivered drug to the ICB with low or undetectable drug levels in ocular surface and extraocular tissues. Use of Bimatoprost SR for glaucoma treatment may reduce the incidence of adverse events typically associated with topical PGAs by targeting bimatoprost delivery to the key site of action of the PGA class and reducing exposure to off-target tissues.

Purpose: To evaluate the effectiveness and safety of oral memantine as a potential neuroprotective agent in open-angle glaucoma (OAG) at risk for progression., Design: Two randomized, double-masked, placebo-controlled, parallel-group, multicenter, 48-month studies identically designed, initiated 1 year apart, and completed in 2006. Protocol amendments included a 1-year extension (first study) and change in primary endpoint and analysis (second study)., Participants: Patients (2298 total) with bilateral OAG; glaucomatous optic disc damage and visual field loss in 1 eye; glaucomatous optic disc damage and/or visual field loss in the contralateral eye (at screening), topically treated or untreated intraocular pressure (IOP) of 21 mmHg or less (at baseline); and at risk of glaucomatous progression (per prespecified criteria)., Methods: Patients were randomized 3:2:2 to receive memantine 20 mg, memantine 10 mg, or placebo tablets daily. Glaucomatous progression was assessed in the intent-to-treat population by full-threshold standard automated perimetry (SAP), frequency doubling technology (FDT), and stereoscopic optic disc photographs, standardized by quality control assessment at centralized reading centers. Safety evaluations included adverse events (AEs), best-corrected visual acuity, biomicroscopy, IOP, and ophthalmoscopy. Efficacy data from each study were analyzed per protocol. Pooled analyses of efficacy and safety data were also performed., Main Outcome Measures: The predefined primary efficacy measure was glaucomatous visual field progression, as measured by SAP. Additional efficacy measures included glaucomatous progression of visual field (FDT) and optic nerve damage (stereoscopic optic disc photographs)., Results: The proportion of patients who completed the studies was similar among groups (80%-83%). Compared with placebo, daily treatment with memantine 10 mg or 20 mg for 48 months did not delay glaucomatous progression significantly in the individual studies and pooled analyses. The pooled risk reduction ratio (95% confidence interval) assessed by SAP was -0.13 (-0.40, 0.09) and -0.17 (-0.46, 0.07) for memantine 10 mg and 20 mg, respectively. Results were similar per FDT and stereoscopic optic disc photographs. The most common AEs leading to treatment discontinuations were dizziness, headache, fatigue, and nausea., Conclusions: With technologies available when the studies were conducted, daily treatment with memantine over 48 months was not shown to prevent glaucomatous progression in this patient population., (Copyright © 2018 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the safety and intraocular pressure (IOP)-lowering effect of a biodegradable bimatoprost sustained-release implant (Bimatoprost SR)., Design: Phase I/II, prospective, 24-month, dose-ranging, paired-eye controlled clinical trial., Methods: At baseline following washout, open-angle glaucoma patients (n = 75) were administered Bimatoprost SR (6 μg, 10 μg, 15 μg, or 20 μg) intracamerally in the study eye; the fellow eye began topical bimatoprost 0.03% once daily. Rescue topical IOP-lowering medication or a single repeat treatment with implant was allowed. The primary endpoint was IOP change from baseline. The main safety measure was adverse events. Results through month 6 are reported., Results: Bimatoprost SR provided rapid, sustained IOP lowering. Overall mean IOP reduction from baseline through week 16 in study eyes was 7.2, 7.4, 8.1, and 9.5 mm Hg with the 6-μg, 10-μg, 15-μg, and 20-μg dose strengths of implant, respectively, vs 8.4 mm Hg in topical bimatoprost-treated pooled fellow eyes (data censored at rescue/retreatment). Rescue/retreatment was not required in 91% and 71% of study eyes up to week 16 and month 6, respectively. Adverse events in study eyes usually occurred within 2 days after the injection procedure and were transient. Conjunctival hyperemia with onset later than 2 days after the injection procedure was more common with topical bimatoprost than Bimatoprost SR (17.3% vs 6.7% of eyes)., Conclusions: Bimatoprost SR demonstrated favorable efficacy and safety through 6 months. All dose strengths were comparable to topical bimatoprost in overall IOP reduction through week 16. A single administration controlled IOP in the majority of patients for up to 6 months., (Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.)

Aim: To compare the efficacy and safety of single-dose bimatoprost 0.03%/timolol 0.5% preservative-free (PF) ophthalmic solution with bimatoprost 0.03%/timolol 0.5% ophthalmic solution in patients with open-angle glaucoma or ocular hypertension., Methods: In this multicentre, randomised, parallel-group study, patients were randomised to bimatoprost/timolol PF or bimatoprost/timolol once daily in the morning for 12 weeks. Primary efficacy endpoints, reflecting differing regional regulatory requirements, included change from baseline in worse eye intraocular pressure (IOP) in the per-protocol population at week 12, and the average eye IOP at weeks 2, 6 and 12 in the intent-to-treat population., Results: 561 patients were randomised (278 to bimatoprost/timolol PF; 283 to bimatoprost/timolol); 96.3% completed the study. Both treatment groups showed statistically and clinically significant mean decreases from baseline in worse eye IOP and in average eye IOP at all follow-up time points (p<0.001). Bimatoprost/timolol PF met all pre-established criteria for non-inferiority and equivalence to bimatoprost/timolol. Ocular adverse events were similar between treatment groups, with conjunctival hyperaemia being the most frequent. Most were mild or moderate in severity., Conclusions: Bimatoprost/timolol PF demonstrated non-inferiority and equivalence in IOP lowering compared with bimatoprost/timolol, with no significant differences in safety and tolerability., Trial Registration Number: NCT01177098., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Background/aim: To evaluate efficacy and safety of bimatoprost 0.03% preservative-free (PF) ophthalmic solution versus bimatoprost 0.03% (Lumigan) ophthalmic solution for glaucoma or ocular hypertension., Methods: In this double-masked, parallel-group study, patients were randomised to bimatoprost PF or bimatoprost for 12 weeks. The primary analysis for non-inferiority was change from baseline in worse eye intraocular pressure (IOP) in the per-protocol population at week 12. For equivalence, it was average eye IOP in the intent-to-treat population at each time point at weeks 2, 6 and 12., Results: 597 patients were randomised (bimatoprost PF, n=302 and bimatoprost, n=295). The 95% CI upper limit for worse eye IOP change from baseline was <1.5 mm Hg at each week 12 time point, meeting prespecified non-inferiority criteria. The 95% CI upper limit for the treatment difference for average IOP was 0.69 mm Hg and the lower limit was -0.50 mm Hg at all follow-up time points (hours 0, 2 and 8 at weeks 2, 6 and 12), meeting equivalence criteria. Both treatments showed decreases in mean average eye IOP at all follow-up time points (p<0.001), were safe and well tolerated., Conclusions: Bimatoprost PF is non-inferior and equivalent to bimatoprost in its ability to reduce IOP-lowering with a safety profile similar to bimatoprost.

Low-level hyperbaric exposure antagonizes a broad range of behavioral effects of ethanol in a direct, reversible, and competitive manner. This study investigates the selectivity of the antagonism across other drugs. C57BL/6 mice were injected with saline, ethanol, n-propanol, or morphine sulfate, and then were exposed to 1 atmosphere absolute (ATA) air, 1 ATA helium-oxygen gas mixture (heliox), or 12 ATA heliox. Locomotor activity was measured from 10 to 40 min following injection. N-propanol produced a dose-dependent depression of locomotor activity from 1.0 g/kg. Morphine produced a dose-dependent stimulation of locomotor activity at doses of 3.75-12.0 mg/kg. Exposure to 12 ATA heliox significantly antagonized the locomotor depressant effects of 1.0 g/kg n-propanol and 2.5 g/kg ethanol, without significantly affecting blood concentrations of these drugs measured at 40 min postinjection. Exposure to 12 ATA heliox did not significantly antagonize the locomotor-stimulating effects of the two morphine doses tested (3.75 and 7.5 mg/kg). These findings suggest that exposure to 12 ATA heliox antagonizes the behavioral effects of intoxicant-anesthetic drugs like ethanol and n-propanol, which are believed to act via perturbation or allosteric modulation of functional proteins, but does not antagonize the effects of drugs like morphine, which act via more direct mechanisms. This demonstration of selective antagonism adds important support for the hypothesis that low-level hyperbaric exposure is a direct mechanistic ethanol antagonist, with characteristics similar to a competitive pharmacological antagonist.

Manipulation of body temperature during intoxication significantly alters brain sensitivity to ethanol. The current study tested the generality of this effect within the hypnotic dose range. Drug naive, male C57BL/6J mice were injected with 3.2, 3.6, or 4.0 g/kg ethanol (20% w/v) and were exposed to 1 of 7 designated temperatures from 13 degrees to 34 degrees C to manipulate body temperature during intoxication. Rectal temperature at return of righting reflex (RORR) was significantly, positively correlated with loss of righting reflex (LORR) duration and significantly, negatively correlated with blood ethanol concentration (BEC) at RORR at all three doses. These results indicate that increasing body temperature during intoxication increased ethanol sensitivity in C57 mice at all three doses tested and demonstrate the generality of temperature dependence across hypnotic doses in these animals. Interestingly, the LORR duration was dose-dependent at each ambient temperature, but the degree of body temperature change and the BEC at RORR were not dose-dependent. Overall, these results emphasize the importance of body temperature as a variable in ethanol research.

Hyperbaric exposure antagonizes ethanol's behavioral effects in a wide variety of species. Recent studies indicating that there are genetically determined differences in the effects of body temperature manipulation on ethanol sensitivity suggested that genotype might also influence the effects of hyperbaric exposure on ethanol intoxication. To investigate this possibility, ethanol injected long sleep (LS)/Ibg (2.7 g/kg), short sleep (SS)/Ibg (4.8 g/kg), 129/J (2.9 g/kg), and C57BL/6J (3.6 g/kg) mice were exposed to one atmosphere absolute (ATA) air or to one or 12 ATA helium-oxygen (heliox) at ambient temperatures selected to offset ethanol and helium-induced hypothermia. Hyperbaric exposure significantly reduced loss of righting reflex (LORR) duration in LS, 129, and C57 mice, but not in SS mice. A second experiment found that hyperbaric exposure significantly reduced LORR duration and increased the blood ethanol concentration (BEC) at return of righting reflex (RORR) in LS mice, but did not significantly affect either measure in SS mice. These results indicate that exposure to 12 ATA heliox antagonizes ethanol-induced LORR in LS, 129 and C57 mice, but not in SS mice. Taken with previous results, the present findings suggest that the antagonism in LS, 129, and C57 mice reflects a pressure-induced decrease in brain sensitivity to ethanol and that the lack of antagonism in SS mice cannot be explained by pressure-induced or genotypic differences in ethanol pharmacokinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study characterized the relationship between brain temperature, rectal temperature, and ethanol sensitivity in the selectivity bred long-sleep (LS) and short-sleep (SS) mice. Radiotelemetric brain probe implanted and nonimplanted LS/lbg and SS/lbg male mice were injected with 2.5 and 4.9 g/kg ethanol, respectively, before exposure to ambient temperatures of 15 degrees C, 22 degrees C, or 34 degrees C. Ambient temperature significantly affected rectal temperature, brain temperature, and ethanol sensitivity, measured by impairment of righting reflex. Brain and rectal temperatures at return of righting reflex (RORR) were highly correlated. In SS mice brain and rectal temperatures at RORR were significantly positively correlated with loss of righting reflex (LORR) duration and significantly negatively correlated with blood ethanol concentration (BEC) at RORR. In LS mice rectal temperature at RORR was significantly negatively correlated with LORR duration, while both brain and rectal temperature at RORR were significantly positively correlated with BEC at RORR. The strength of the correlations and r2 values generated from linear regression analysis indicates that body temperature during intoxication can explain up to 52% of the variability in ethanol sensitivity in SS mice, but only 19% of the variability in ethanol sensitivity in LS mice. The correlational analyses are consistent with previous results based on comparisons between rectal temperature and ethanol sensitivity and extend to direct brain temperature measurement the evidence that decreasing temperature during intoxication decreases ethanol sensitivity in SS mice and increases ethanol sensitivity in LS mice.(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction between temperature and ethanol-induced fluidization was investigated in brain synaptic plasma membranes from C57BL/6 mice. Changes in fluidity were measured using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Fluorescence polarization was tested in the presence and absence of ethanol at 25, 32 and 37 degrees C. An increase in temperature resulted in a significant increase in the baseline fluidity of the membranes and an increase in the magnitude of ethanol-induced fluidization of brain membranes. The combined effect of temperature on baseline fluidity and the magnitude of the response to ethanol resulted in a significant temperature-related increase in the relative response to ethanol (% change in polarization). The minimum concentration of ethanol required to cause a significant increase in the fluidity of the membranes was 170.7 mM at 25 degrees C and 85.3 mM at both 32 and 37 degrees C. The present results indicate that temperature-related changes in the effects of ethanol on membrane properties may underlie the effects of temperature on ethanol sensitivity in C57 mice.

The effect of body temperature on ethanol (ETOH) or ethanol plus pentobarbital (ETOH/PB) lethality was investigated in C57BL/6J mice. Decreasing ambient temperatures from 35-20 degrees C, decreased rectal temperatures from 38-20 degrees C and increased 8-hour survival from 0-93% for ETOH-treated and from 0-100% for ETOH/PB-treated mice. ETOH and ETOH/PB animals with no hypothermia (body temperatures = 38 degrees C) had the highest lethality. Those with body temperatures between 30-32 degrees C had the highest 24-hour survival. These results suggest that controlled hypothermia may be useful in reducing lethality from ethanol or ethanol/combination overdoses.

Previous studies have found that body temperature during intoxication influences brain sensitivity to ethanol with the sensitivity being less at cool than at warm body temperatures. If this effect of temperature reflects alterations in the acute membrane perturbing action of ethanol, as suggested by in vitro studies, then body temperature reduction (hypothermia) during tolerance acquisition should reduce the effectiveness of a given ethanol concentration and, in turn, should reduce the development of chronic functional ethanol tolerance. To test this hypothesis, adult drug-naive C57BL/6J mice were injected i.p. once daily for five days with 3.6 g/kg ethanol (20% w/v) and were exposed to 34 degrees C or 25 degrees C for five hours following injection. On day 6, both ethanol acquisition groups and naive mice were injected i.p. with 4.0 g/kg ethanol and exposed to 25 degrees C. During acquisition, the group exposed to 34 degrees C had significantly higher body temperatures than the mice exposed to 25 degrees C, and there were no statistically significant differences in blood ethanol concentrations between treatment conditions. The extent of tolerance on day 6, measured by sleep-times and wake-up blood and brain ethanol concentrations versus naive mice, was significantly greater in the 34 degrees C acquisition group than in the 25 degrees C acquisition group. The results demonstrate that body temperature influences tolerance development in the manner predicted by membrane perturbation theories of anesthesia and adaptation based tolerance theories.

The structure of a fibronectin molecule has been studied by circular dichroism, infrared spectroscopy, scanning microcalorimetry and electron microscopy. It has been shown that the secondary structure of fibronectin is formed exclusively by the antiparallel beta-form -- 35%; the fibronectin molecule consists of several domains; the protein has a compact structure, the length of the molecule is 15.5 +/- 1.3 nm, the width is 8.8 +/- 1.7 nm, the axial ratio is approximately 2:1.1.

The present study investigated the importance of body temperature during intoxication in mediating differences between five inbred strains of mice (C57BL/6J; BALB/cJ; DBA/2J; A/HeJ; 129/J) in their acute sensitivity to the hypnotic effects of ethanol. Mice exposed to 22 degrees C after ethanol injection became hypothermic and exhibited statistically significant differences between strains in rectal temperatures at the return of the righting reflex (RORR), duration of loss of the righting reflex (LORR), and blood and brain ethanol concentrations at RORR. Exposure to 34 degrees C after injection offset ethanol-hypothermia and markedly reduced strain-related differences in rectal temperatures and blood and brain ethanol concentrations at RORR. Brain ethanol concentrations at RORR were significantly lower in C57, BALB, DBA and A/He mice exposed to 34 degrees C compared to mice exposed to 22 degrees C during intoxication suggesting that offsetting hypothermia increased ethanol sensitivity in these strains. Taken with previous in vitro studies, these results suggest that genetically determined differences in acute sensitivity to the behavioral effects of ethanol reflect differences in body temperature during intoxication as well as differences in sensitivity to the initial actions of ethanol at the cellular level.