Facilitation by 3,4-diaminopyridine of regenerative acetylcholine release from mouse motor nerve.

1. Effects of 3,4-diaminopyridine (DAP) on endplate potentials (e.p.ps) were studied in mouse phrenic nerve-hemidiaphragms. 2. In cut muscle preparations, low concentrations of DAP (2-20 microns) increased the amplitude of e.p.ps and shifted the curve relating Ca2+ concentration to e.p.p. amplitude leftward. 3. High concentration of DAP (40-4000 microns) prolonged the duration of e.p.ps dose-dependently up to one hundred fold (ca. 200 ms), yielding, in addition to the normal phasic e.p.p., a prolonged plateau depolarization component which was often preceded by an upstroke depolarization. During the plateau depolarization, nerve stimulations did not evoke any e.p.p. 4. The plateau component of prolonged e.p.ps was suppressed by tubocurarine, verapamil, nifedipine, Mn2+ and Cd2+ (but not by atropine) at low concentrations that had negligible effect on the amplitude of miniature e.p.ps or the phasic component of e.p.ps. Abolition of the plateau component by these agents restored the capability of the nerve terminal to evoke e.p.ps on nerve stimulation. 5. Low concentrations of neostigmine (0.01-0.02 microns) markedly lengthened DAP-prolonged e.p.ps. However, the regenerative endplate depolarization evoked in the presence of high concentrations of neostigmine (0.3-0.5 microns) was not prolonged by DAP. 6. Tetraethylammonium (1 mM) did not provoke prolonged e.p.ps but acted cooperatively with DAP to prolong the duration of plateau depolarization. At a high concentration (3 mM), tetraethylammonium depressed the amplitude of miniature e.p.ps and abolished DAP-prolonged e.p.ps. 7. In uncut muscle preparations, DAP apparently did not modify the time course and amplitude of miniature e.p.ps.(ABSTRACT TRUNCATED AT 250 WORDS)     

Formulation and stability of hospital preparation of 3,4-diaminopyridine capsules

Administration of 3,4-diamynopyridine (3,4-DAP) has been found to be effective in the symptomatic treatment of patients with Eaton-Lambert Myasthenic syndrome. A recent case of this syndrome in Val de Grace Military hospital led us to manufacture 3,4-DAP capsules. In agreement with good manufactoring processes, we have performed mass uniformity and content tests. Six different formulations were tested, starch maize and magnesium stearate have been validated as excipients. The stability study showed that the conservation was good even under extreme conditions. Clinical and electromyographic improvement seen in this patient suggests this preparation may be of benefit.     

Effect of 4-aminopyridine and 3,4-diaminopyridine on guinea-pig isolated ileum

1 4-Aminopyridine and 3,4-diaminopyridine produced concentration-dependent contraction on guinea-pig isolated ileum incubated in Tyrode solution. The EC₅₀ values were 1.14 × 10^?4 and 1.39 × 10^?4M , respectively. 2 Calcium channel blockers such as verapamil, diltiazem, nifedipine, flunarizine, and lanthanum chloride antagonized the contracting effect induced by 4-aminopyridine and 3,4-diaminopyridine in guinea-pig isolated ileum. 3 Diazoxide and atropine sulphate behaved similarly as antagonists of the contracting effect induced by 4-aminopyridine and 3,4-diaminopyridine in guinea-pig isolated ileum. 4 It is concluded that the aminopyridines exert their effects through the release of acetylcholine from parasympathetic nerve terminals.     

Ineffectiveness of 3,4-diaminopyridine as a therapy for type C botulism

Clostridium botulinum neurotoxins inhibit acetylcholine release at neuromuscular junctions. Agents stimulating neurotransmitter efflux, such as 3,4-diaminopyridine (3,4-DAP), could be useful for botulism therapy. Treatment with 3,4-DAP (8 mg/kg hourly, beginning 3 hr after toxin injection) failed to increase the survival times of mice receiving 10, 20 or 40 LD50 type C, but did prolong the survival of those receiving 20 LD50 type A. This difference in 3,4-DAP efficacy may reflect variations in the molecular mechanism of action of types A and C botulinum neurotoxins.     

Microencapsulation of acetaminophen into poly(L-lactide) by three different emulsion solvent-evaporation methods

Poly(L-lactide) (PLLA) microcapsules containing acetaminophen (APAP) were prepared by three emulsion solvent-evaporation methods including an O/W-emulsion method, an O/W-emulsion co-solvent method and a W/O/W-multiple-emulsion method. The average size and morphology of the microcapsules varied substantially among these three preparation methods. Various alcohol and alkane co-solvents were found to exert significant impact on the O/W-emulsion co-solvent method and a more lipophilic co-solvent such as heptane appeared to enhance drug encapsulation with an efficiency nearly double of the O/W-emulsion method. When a small amount of water was added as the internal aqueous phase in the W/O/W-multiple-emulsion method, the encapsulation efficiency was found nearly triple of that for the O/W-emulsion method. While having a higher encapsulation efficiency, the microcapsules prepared by the W/O/W-multiple-emulsion method had as good controlled release behaviour as those prepared by the O/W-emulsion method. The release kinetics of microcapsules prepared by the O/W-emulsion method and the O/W-emulsion co-solvent (alcohol) method fitted the Higuchi model well in corroboration with the uniform distribution of APAP in PLLA matrix, i.e. the monolithic type microcapsules. However, the release kinetics of microcapsules prepared by the O/W-emulsion co-solvent (alkane) method and the W/O/W-multiple-emulsion method fitted the first-order model better, indicating the reservoir type microcapsules.     

Microencapsulation of acetaminophen into poly(L-lactide) by three different emulsion solvent-evaporation methods

Poly(L-lactide) (PLLA) microcapsules containing acetaminophen (APAP) were prepared by three emulsion solvent-evaporation methods including an O/W-emulsion method, an O/W-emulsion co-solvent method and a W/O/W-multiple-emulsion method. The average size and morphology of the microcapsules varied substantially among these three preparation methods. Various alcohol and alkane co-solvents were found to exert significant impact on the O/W-emulsion co-solvent method and a more lipophilic co-solvent such as heptane appeared to enhance drug encapsulation with an efficiency nearly double of the O/W-emulsion method. When a small amount of water was added as the internal aqueous phase in the W/O/W-multiple-emulsion method, the encapsulation efficiency was found nearly triple of that for the O/W-emulsion method. While having a higher encapsulation efficiency, the microcapsules prepared by the W/O/W-multiple-emulsion method had as good controlled release behaviour as those prepared by the O/W-emulsion method. The release kinetics of microcapsules prepared by the O/W-emulsion method and the O/W-emulsion co-solvent (alcohol) method fitted the Higuchi model well in corroboration with the uniform distribution of APAP in PLLA matrix, i.e. the monolithic type microcapsules. However, the release kinetics of microcapsules prepared by the O/W-emulsion co-solvent (alkane) method and the W/O/W-multiple-emulsion method fitted the first-order model better, indicating the reservoir type microcapsules.     

Sensitive trace-first liquid chromatographic determination of 4-aminopyridine in 3,4-diaminopyridine

For the treatment of human neuromuscular diseases, 3,4-diaminopyridine (DAP) is six to ten times more effective than 4-aminopyridine (AP), but only half as convulsant and toxic. Therefore, there is a need for the determination of AP in DAP. With only conventional equipment, high-pressure liquid chromatography can be used for the extremely sensitive detection of a trace contaminant under one condition: that is, the trace must be eluted before the major component it contaminates. Prior elution presents a trace peak in a fully exploitable form that is maximally efficient and maximally observable. This has already been demonstrated with a Pirkle-concept chiral stationary phase for determination of a chiral trace. However, its application to determination of a nonchiral trace with a reversed phase has not previously been reported. Such an application is reported here. In this demonstrative study, selectivity and loading capability were iteratively improved. Ion pairing with dodecanesulfonate maximized selectivity. It was again shown that using a less concentrated sample in greater volume maximizes loading capability without obscuring the peak of the trace. Eventually, the ability to detect 0.005% AP in DAP was demonstrated. Whether that sensitivity might be improved still more, perhaps with a larger column, was not established.     

Effects of vasodilators on cyclic contraction induced by 3,4-diaminopyridine in isolated porcine coronary arteries

3,4-Diaminopyridine (3,4-DAP), which is known to decrease K conductance, produced spontaneous repetitive phasic contractions of a regular (28/60) and an irregular (15/60) cycle or tonic contraction (16/60) following a latent period of 5-100 min in isolated porcine coronary arteries. Effects of pinacidil, a newly-synthesized vasodilator, were investigated using the preparation in which 3,4-DAP produced phasic contractions of the regular cycle in comparison with those of various vasodilators. Pinacidil produced dose-dependent prolongation of the cycle and reduced the peak tension and the tension at the relaxation phase, a mode of action that closely resembles that of nicorandil, suggesting the increase in K conductance and hyperpolarization. Nifedipine (10(-8) M) and dilazep (10(-4) M) markedly reduced the peak tension, while adenosine, dipyridamole and nitroglycerin did not produce such effects. The latter three drugs produced a prolongation of the cycle and reduced the tension of the relaxation phase. These data suggest that reduction of K conductance and activation of the voltage-dependent Ca channel may play an important role in initiation of the spontaneous repetitive phasic contraction in porcine coronary artery.     

A comparison of 3,4-diaminopyridine and 4-aminopyridine in the anaesthetized cat

3,4-Diaminopyridine and 4-aminopyridine were compared in the anaesthetized cat and found to be equiactive in their anti-curare activity. This in vivo similarity is at variance with previous in vitro studies which demonstrate 3,4-diaminopyridine to be more active than 4-aminopyridine at the neuromuscular junction. Possible reasons for the similarity between the two aminopyridines at the in vivo neuromuscular junction are discussed and it is concluded that 3,4-diaminopyridine has only marginal advantages over 4-aminopyridine as a potential anti-curare agent.     

Synaptic facilitatory and depressant actions of 3,4-diaminopyridine: correlation with anticurare properties

This study aimed to define the complete concentration-effect relationship for anticurare effects of 3,4-diaminopyridine (3,4-DAP) in the isolated sympathetic ganglion of the bullfrog. Synaptic transmission was monitored by extracellular and intracellular recordings of the postganglionic response to preganglionic stimulation. A previous study showed that in the bullfrog sympathetic ganglion 3,4-DAP caused stimulus-bound repetitive postganglionic responses (SBR) to each single preganglionic stimulus. The concentration-effect relationship for 3,4-DAP-induced SBR was bell-shaped, and the descending limb of the curve reflected progressive suppression of SBR while normal synaptic transmission was maintained. In the present study a detailed concentration-effect analysis of 3,4-DAP's anticurare action also resulted in a bell-shaped curve nearly congruent with that for SBR. SBR and anticurare effects of 3,4-DAP therefore occupy a common concentration-effect domain, and this suggests that a common mechanism (increased transmitter release) may account for both effects.     

Equipotency of anti-curare activity of 4-aminopyridine and 3,4-diaminopyridine in anesthetized rats

In the curarized preparation, 3,4-diaminopyridine (3,4-DAP) and 4-aminopyridine (4-AP) were equiactive in their ability to antagonize d-tubocurarine caused complete depression of the indirectly elicited twitches of the sciatic nerve-tibialis anterior muscle preparation in anesthetized rats. In the non-curarized preparation, 3,4-DAP showed 2.3 to 4.0 times stronger augmentation of the indirectly elicited twitches than 4-AP, but both the drugs increased equivalently and slightly the maximally elicited twitches of the chronically denervated muscle. The results suggest that the difference of their prejunctional effects is masked by the postjunctional effects of d-tubocurarine in the indirectly elicited twitches.     

聚乙烯醇微球的制备与研究

目的:制备聚乙烯醇微球,用于静脉注射靶向给药研究。方法:通过将溶有戊二醛的乙醚加入到以聚乙烯醇水溶液为水相、正庚烷为油相的乳液中作为交联剂,将微量浓盐酸滴加到乳液中作为催化剂,乳化聚合制备出聚乙烯醇微球,并考察了聚乙烯醇溶液浓度、搅拌速度及油水相比例等对微球粒径及形貌的影响。结果:在聚乙烯醇浓度为5.0%,搅拌速度为14000r·min~(-1)条件下,制备的微球平均粒径为1.9μm。且聚乙烯醇浓度越高,微球平均粒径越大,单分散性越差;搅拌速度越高,微球平均粒径越小,单分散性越好。结论:通过调整聚乙烯醇浓度和搅拌速度,可以得到1～15μm范围内不同平均粒径的微球。     

Effects of 3,4-diaminopyridine on mechanical and electrical responses of frog single muscle fibres

The effects of 3,4-diaminopyridine (3,4-DAP) were studied on isolated muscle fibres of the frog in concentrations ranging between 0.025 and 5.0 mM. Isometric twitch and tetanus responses were recorded at temperatures between 2.5 and 3.9 degrees. 3,4-DAP caused a concentration-dependent increase in twitch amplitude, maximum effects being obtained at a concentration of 3 mM with a mean increase in tension of 70 +/- 12% of control (n = 7). 3,4-DAP in 3 mM concentration had only a slight increase in initial rate of rise of twitch tension (mean increase 8 +/- 4%) but increased the time to half peak tension by 59 +/- 9% and the time from peak tension to half relaxation by 78 +/- 10%. No significant effect of 3,4-DAP was observed on the initial rate of rise and total amplitude of the isometric tetanus. The twitch potentiating effect of 3,4-DAP developed gradually with the number of times the fibre was stimulated and reached a maximum level after 40-50 stimulations. A gradual increase in the duration of the action potential was also observed. It is suggested that 3,4-DAP, like 4-aminopyridine, potentiates the twitch by means of prolonging the duration of the action potential.     

Preparation of acetazolamide composite microparticles by supercritical anti-solvent techniques

The possibility of preparation of ophthalmic drug delivery systems using compressed anti-solvent technology was evaluated. Eudragit RS 100 and RL 100 were used as drug carriers, acetazolamide was the model drug processed. Compressed anti-solvent experiments were carried out as a semi-continuous or a batch operation from a liquid solution of polymer(s)+solute dissolved in acetone. Both techniques allowed the recovery of composite particles, but the semi-continuous operation yielded smaller and less aggregated populations than the batch operation. The release behaviour of acetazolamide from the prepared microparticles was studied and most products exhibited a slower release than the single drug. Moreover, the release could be controlled to some extent by varying the ratio of the two Eudragit used in the formulation and by selecting one or the other anti-solvent technique. Simple diffusion models satisfactorily described the release profiles. Composites specifically produced by semi-continuous technique have a drug release rate controlled by a diffusion mechanism, whereas for composites produced by the batch operation, the polymer swelling also contributes to the overall transport mechanism.     

4-氨基吡啶和3,4-二氨基吡啶对兔实验性自身免疫重症肌无力的治疗

以N-AChR膜微囊免疫家兔,造成重症肌无力模型,iv 4-AP 0.8 mg·kg~(-1)后病兔的肌无力症状迅速缓解。以4Hz电流刺激坐骨神经,腓肠肌复合肌电位和足趾收缩即由递减变为整齐;50Hz电流引起的强直收缩能保持。作用维持9.1±2.5h。iv 3,4-DAP 0.4mg·kg~(-1)可获相似效果,持续9.3±3.1h。两药有明显的对症治疗作用。