In Vivo Photoadduction of Anesthetic Ligands in Mouse Brain Markedly Extends Sedation and Hypnosis.

Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the potential to further define critical neuroanatomic targets of drug action. In the brains of WT male mice, we demonstrate the feasibility of using photoaffinity ligands in vivo to prolong anesthesia via targeted yet spatially restricted photoadduction of azi-m-propofol (aziPm), a photoreactive analog of the general anesthetic propofol. Systemic administration of aziPm with bilateral near-ultraviolet photoadduction in the rostral pons, at the border of the parabrachial nucleus and locus coeruleus, produced a 20-fold increase in the duration of sedative and hypnotic effects compared with control mice without UV illumination. Photoadduction that missed the parabrachial-coerulean complex also failed to extend the sedative or hypnotic actions of aziPm and was indistinguishable from nonadducted controls. Paralleling the prolonged behavioral and EEG consequences of on target in vivo photoadduction, we conducted electrophysiologic recordings in rostral pontine brain slices. Using neurons within the locus coeruleus to further highlight the cellular consequences of irreversible aziPm binding, we demonstrate transient slowing of spontaneous action potentials with a brief bath application of aziPm that becomes irreversible on photoadduction. Together, these findings suggest that photochemistry-based strategies are a viable new approach for probing CNS physiology and pathophysiology.SIGNIFICANCE STATEMENT Photoaffinity ligands are drugs capable of light-induced irreversible binding, which have unexploited potential to identify the neuroanatomic sites of drug action. We systemically administer a centrally acting anesthetic photoaffinity ligand in mice, conduct localized photoillumination within the brain to covalently adduct the drug at its in vivo sites of action, and successfully enrich irreversible drug binding within a restricted 250 µm radius. When photoadduction encompassed the pontine parabrachial-coerulean complex, anesthetic sedation and hypnosis was prolonged 20-fold, thus illustrating the power of in vivo photochemistry to help unravel neuronal mechanisms of drug action.

HCN1 channels as targets for anesthetic and nonanesthetic propofol analogs in the amelioration of mechanical and thermal hyperalgesia in a mouse model of neuropathic pain.

Chronic pain after peripheral nerve injury is associated with afferent hyperexcitability and upregulation of hyperpolarization-activated, cyclic nucleotide-regulated (HCN)-mediated IH pacemaker currents in sensory neurons. HCN channels thus constitute an attractive target for treating chronic pain. HCN channels are ubiquitously expressed; analgesics targeting HCN1-rich cells in the peripheral nervous system must spare the cardiac pacemaker current (carried mostly by HCN2 and HCN4) and the central nervous system (where all four isoforms are expressed). The alkylphenol general anesthetic propofol (2,6-di-iso-propylphenol) selectively inhibits HCN1 channels versus HCN2-HCN4 and exhibits a modest pharmacokinetic preference for the periphery. Consequently, we hypothesized that propofol, and congeners, should be antihyperalgesic. Alkyl-substituted propofol analogs have different rank-order potencies with respect to HCN1 inhibition, GABA(A) receptor (GABA(A)-R) potentiation, and general anesthesia. Thus, 2,6- and 2,4-di-tertbutylphenol (2,6- and 2,4-DTBP, respectively) are more potent HCN1 antagonists than propofol, whereas 2,6- and 2,4-di-sec-butylphenol (2,6- and 2,4-DSBP, respectively) are less potent. In contrast, DSBPs, but not DTBPs, enhance GABA(A)-R function and are general anesthetics. 2,6-DTBP retained propofol's selectivity for HCN1 over HCN2-HCN4. In a peripheral nerve ligation model of neuropathic pain, 2,6-DTBP and subhypnotic propofol are antihyperalgesic. The findings are consistent with these alkylphenols exerting analgesia via non-GABA(A)-R targets and suggest that antagonism of central HCN1 channels may be of limited importance to general anesthesia. Alkylphenols are hydrophobic, and thus potential modifiers of lipid bilayers, but their effects on HCN channels are due to direct drug-channel interactions because they have little bilayer-modifying effect at therapeutic concentrations. The alkylphenol antihyperalgesic target may be HCN1 channels in the damaged peripheral nervous system.

Fospropofol disodium, a water-soluble prodrug of the intravenous anesthetic propofol (2,6-diisopropylphenol).

BACKGROUND: Today, propofol or 2,6-diisopropylphenol is the anesthetic mainly used for monitored anesthetic care sedation and during intravenous anesthesia. The formulation, a lipid macroemulsion, shows several disadvantages. Therefore, during the past years considerable scientific effort has been undertaken to find either a better formulation or a prodrug of propofol. Fospropofol is the first propofol prodrug that has been intensively studied in man. It has been licensed in 2008 by the FDA for monitored anesthetic care sedation. OBJECTIVES AND METHODS: This review describes first published study results of fospropofol with regard to its pharmacokinetics/pharmacodynamics, drug safety, tolerability and drug side effects. Using a Medline search all published articles and abstracts containing the words fospropofol or GPI 15715 were included. RESULTS AND CONCLUSION: As the impact of an errorness drug assay for propofol liberated from fospropofol is not exactly defined, no clear conclusions can be drawn from the first published pharmacokinetic/pharmacodynamic studies. Fospropofol was well tolerated in the first two clinical studies and no serious side effects were reported. After characterization of the true pharmacokinetic/pharmacodynamics profile, fospropofol, an aqueous solution, has the potential to favorably compare with benzodiazepines for procedural sedation and also may be used for long-term sedation and intravenous anesthesia.

Propofol (Diprivan-EDTA) counteracts oxidative injury and deterioration of the arterial oxygen tension during experimental septic shock.

PURPOSE: Human septic shock can be replicated in the endotoxaemic pig. Endotoxaemia causes a multitude of events, including reduced PaO(2) and increased lipid peroxidation. This study was designed to evaluate the possible effects of a commonly used anaesthetic drug with known antioxidant properties (propofol) during porcine endotoxaemia. METHODS: Ten pigs were anaesthetised and given a 6 h E. coli endotoxin infusion. The animals received, randomly, a supplementary continuous infusion of propofol emulsion (containing 0.005% EDTA) or the corresponding volume of vehicle (controls). Pathophysiologic responses were determined. Non-enzymatic (by measuring plasma 8-iso-PGF(2 alpha) and enzymatic (by measuring plasma 15-keto-dihydro-PGF(2 alpha)) lipid peroxidations were evaluated. Plasma levels of the endogenous antioxidants alpha- and gamma-tocopherols, were also analysed. RESULTS: Endotoxaemia increased plasma levels of 8-iso-PGF(2 alpha) (1st-4th h) and 15-keto-dihydro-PGF(2 alpha) (1st-4th h) significantly more in controls than in the propofol+endotoxin group. PaO(2) was significantly less affected by endotoxin in the propofol treated animals (2nd-4th h). Mean arterial pressure (4th-6th h) and systemic vascular resistance (6th h) were reduced significantly more by endotoxin among the propofol-treated animals. Vitamin E (alpha-tocopherol) increased in all animals, significantly more in the propofol+endotoxin group (1/2-6th h) than in the control group. CONCLUSIONS: Propofol reduced endotoxin-induced free radical mediated and cyclooxygenase catalysed lipid peroxidation significantly. The implication is that propofol counteracts endotoxin-induced deterioration of PaO(2).