Ethosomes as delivery system for transdermal administration of vinpocetine.

The purpose of the present study was to develop a novel transdermal vinpocetine patch containing a stable formulation and with good entrapment efficiency, and percutaneous absorption which via ethosome. Ethosome was found to be a more efficient delivery carrier with high encapsulation capacities (79.5% +/- 1.8%) and nanometric size (180.7 +/- 1.5 nm). In vitro percutaneous permeation experiments demonstrated that the permeation of vinpocetine through abdominal skin of Sprague Dawley was significantly increased when ethosome was used. The vinpocetine transdermal fluxes from ethosome gel (3.56 +/- 0.13 microg/cm2/h) were 6.72 and 3.10 times higher than that of vinpocetine gel solution and vinpocetine aueous solution, respectively. Furthermore, the AUC(0 --> infinity), and eliminiation half-life by the transdermal administration were significantly higher than those by the intragastric administration (P < 0.01). The study demonstrated that ethosome is a promising vesicular carrier for enhancing percutaneous absorption of vinpocetine.

Structural dynamics determine voltage and pH gating in human voltage-gated proton channel.

Voltage-gated proton (Hv) channels are standalone voltage sensors without separate ion conductive pores. They are gated by both voltage and transmembrane proton gradient (i.e., ∆pH), serving as acid extruders in most cells. Like the canonical voltage sensors, Hv channels are a bundle of four helices (named S1 -S4), with the S4 segment carrying three positively charged Arg residues. Extensive structural and electrophysiological studies on voltage-gated ion channels, in general, agree on an outwards movement of the S4 segment upon activating voltage, but the real-time conformational transitions are still unattainable. With purified human voltage-gated proton (hHv1) channels reconstituted in liposomes, we have examined its conformational dynamics, including the S4 segment at different voltage and pHs using single-molecule fluorescence resonance energy transfer (smFRET). Here, we provide the first glimpse of real-time conformational trajectories of the hHv1 voltage sensor and show that both voltage and pH gradient shift the conformational dynamics of the S4 segment to control channel gating. Our results indicate that the S4 segment transits among three major conformational states and only the transitions between the inward and outward conformations are highly dependent on voltage and pH. Altogether, we propose a kinetic model that explains the mechanisms underlying voltage and pH gating in Hv channels, which may also serve as a general framework for understanding the voltage sensing and gating in other voltage-gated ion channels.

Effects of chronic, systemic treatment with the dopamine receptor agonist R-apomorphine in partially lesioned rat model of Parkinson's disease: an electrophysiological study of substantia nigra dopamine neurons.

Previous studies have suggested that R-apomorphine (R-APO), a non-selective dopamine (DA) receptor agonist, has neuroprotective effects in the experimental models of Parkinson's disease (PD). In this study, we investigated the effects of chronic, systemic treatment with R-APO in the firing activity of substantia nigra pars compacta (SNc) DA neurons in 6-hydroxydopamine (6-OHDA) partially lesioned rats. In the 6-OHDA-lesioned rats treated with vehicle, injection of 6-OHDA (20.1 microg) into the striatum produced a partial lesion causing 41% loss of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the SNc. In the partially lesioned rats, chronic, systemic treatment of R-APO (10 mg/kg/day, s.c., 11 days) attenuated loss of TH-ir neurons in the SNc. The partial lesion of the nigrostriatal pathway and R-APO treatment did not change the firing rate and firing pattern of DA neurons in the SNc of rats. In contrast, the R-APO treatment increased the number of spontaneously active DA neurons of the SNc in the partially lesioned rats, while the lesion decreased the number of spontaneously active DA neurons. In addition, the chronic R-APO treatment decreased the responsiveness of the DA neurons to intravenously administrated R-APO in the partially lesioned rats. These results indicate that chronic, systemic R-APO treatment has the neuroprotective effect, and reverses the decrease in the number of spontaneously active DA neurons in the SNc whereas the treatment induces a reduction in the sensitivity of DA receptors in the SNc to R-APO stimulation in this model.

Blockade of mGluR5 reverses abnormal firing of subthalamic nucleus neurons in 6-hydroxydopamine partially lesioned rats.

Activation of metabotropic glutamate receptor 5 (mGluRs) in the subthalamic nucleus (STN) results in burst-firing activity of STN neurons, which is similar to that observed in Parkinson's disease (PD). We examined the effects of chronic and systemic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective mGluR5 antagonist, in firing activity of STN neurons in partially lesioned rats by 6-hydroxydopamine (6-OHDA). In 6-OHDA-lesioned rats treated with vehicle, injection of 6-OHDA (4 microg) into the medial forebrain bundle produced a partial lesion causing 36% loss of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNpc). The 6-OHDA lesion in vehicle-treated rats showed an increasing firing rate and a more irregular firing pattern of STN neurons. Whereas chronic, systemic treatment of MPEP (3 mg/kg/day, 14 days) produced neuroprotecive effects on the TH-ir neurons and normalized the hyperactive firing activity of STN neurons in 6-OHDA partially lesioned rats. These data demonstrate that partial lesion of the nigrostriatal pathway increases firing activity of STN neurons in the rat, and chronic, systemic MPEP treatment has the neuroprotective effect and reverses the abnormal firing activity of STN neurons, suggesting that MPEP has an important implication for the treatment of PD.

[Effects of chronic, systemic treatment with metabotropic glutamate receptor 5 antagonist on behavioral activity and neuroprotection in a preclinical rat model of Parkinson's disease].

OBJECTIVE: To study the effects of chronic, systemic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP) on behavioral activity and neuroprotection in the rat with partial lesion of the nigrostriatal pathway. METHODS: A total of 37 male SD rats were randomly divided into sham (n=11), PD+ saline (n=15) and PD+MPEP group (n=11). Rat model of Parkinson's disease was established by injection of 6-OHDA into medial forebrain bundle. PD+vehicle rats and PD+MPEP rats were injected with NS (0.1 mL) and MPEP (3 mg/kg) per day respectively. Changes in the spontaneous and induced behaviors and the degree of dopamimnergic neurons loss in the substantia nigra pars compacta (SNpc) were observed by behavioral and immunocytochemical methods in partially lesioned and MPEP-treated rats. RESULTS: Unilateral injection of 6-hydrodopamine (6-OHDA) into medial forebrain bundle resulted in the moderate loss (39%) of dopaminergic neurons in the SNpc, and MPEP treatment decreased the number of neurons loss compared with PD+saline rats (P < 0.01). In this model, the lesioned rats did not show obviously abnormal posture. However, apomorphine (APO) induced significant rotation behavior, which increases in a time-dependent manner. Chronic, systemic treatment with MPEP could against the toxicity of 6-OHDA, and reduced the loss of SNpc dopaminergic neurons. In addition, MPEP ameliorated significantly the rotation behaviour induced by APO, which is strengthened in a time-dependent manner. CONCLUSION: MPEP treatment has anti-parkinsonian and neuroprotective effects in the rat with partial lesion of the nigrostriatal pathway, and the efficacy gradually increase with the treatment time.