Selective ligands for opioid receptors: β-Cyclopropylalanyl containing analogs of enkephalin

The synthesis and resolution of the amino acid β-cyclopropylalanine (Cpr) and its incorporation into four enkephalin analogs is reported. The analogs prepared were: Tyr - l - Cpr - Gly - Phe - Pen (des - COOH - Nle = n - pentylamide = Pen) (l -Cpr²-Pen⁵-ENK), Tyr-d -Cpr-Gly-Phe-Pen (d -Cpr²-Pen⁵-ENK), l -Cpr-Tyr-d -Ala-Gly-Phe-Pen (l -Cpr⁰-d -Ala²-Pen⁵-ENK) and d -Cpr-Tyr-d -Ala-Gly-Phe-Pen (d -Cpr⁰-d -Ala²-Pen⁵-ENK). Each was tested for its ability to inhibit the field stimulated guinea pig ileum (GPI) and rat vas deferens (RVD) and the results compared to the effect d -Ala²-d -Leu⁵-enkephalin (DADLE) has on the same preparations. The results show that at concentrations up to 10^-5 m all four analogs, as well as DADLE, are full agonists on the GPI preparation. The concentrations necessary to produce a 50% inhibition of the twitch response were, DADLE, 3.5 °× 10^-8 m ; l - Cpr⁰-d -Ala²-Pen⁵-ENK, 6.0 × 10^-8 m ; d -Cpr²-Pen⁵-ENK, 1.1 × 10^-7 m ; l -Cpr²-Pen⁵-ENK, 1.2 × 10^-6 m and d -Cpr⁰-d -Ala²-Pen⁵-ENK, > 10^-5 m . On RVD a different result was observed with only DADLE (1.3 × 10^-6 m ) and l -Cpr⁰-Pen⁵-enkephalin (1.8 × 10^-6 m ) showing full agonist activity. d -Cpr²-Pen⁵-ENK was a partial agonist (29 · 5% inhibition of the twitch at 10^-5 m ) while d -Cpr⁰-d -Ala²-Pen⁵-ENK and l -Cpr²-Pen⁵-ENK did not inhibit the twitch at concentrations up to 10^-5 m . These compounds which were inactive or of low potency on each preparation were also tested as antagonists. Only d -Cpr²-Pen⁵-ENK was an antagonist (pA₂ = 6.09) versus DADLE on RVD while d -Cpr⁰-d -Ala²-Pen⁵-ENK was inactive as an antagonist on both GPI and RVD. d -Cpr²-Pen⁵-ENK, therefore, represents the first enkephalin analog to be categorized as a mixed agonist-antagonist.     

A potent factor in extracts of the skin of the Australian frog, Pseudophryne coriacea. Apparent facilitation of transmitter release in isolated smooth muscle preparations

Extracts of the skin of the Australian frog Pseudophryne coriacea (PsC) displayed potent stimulant effects on isolated smooth muscle preparations of intestine and similar effects on electrically-stimulated vas deferens preparations. These effects must be ascribed to an alkaloid, related in structure to the pumiliotoxins, a class of alkaloid compounds occurring in the skin of neotropical poison frogs. On the basis of results obtained with antagonists and blocking agents, it is suggested that the extract has a pre-synaptic, neurogenic point of attack and that it acts to facilitate the release of transmitters from nerve endings. Acetylcholine is the most important agent involved in the response to the extract by the intestinal muscle and noradrenaline in the response by vas deferens preparations. However, release of other aminergic or peptidergic transmitters may participate, positively or negatively, in the response.     

Pharmacology of B-HT 920 in some Isolated Smooth Muscles of the Guinea-pig

Abstract: The effects of B-HT 920 were investigated on four isolated preparations from the guinea-pig, namely the aorta, trachea, ileum and vas deferens. The latter three preparations were studied during electrical field stimulation, which induced contractions by activating cholinergic neurones (trachea and ileum) or adrenergic neurones (vas deferens), respectively. Comparative studies were also made with clonidine and noradrenaline. In ileum and trachea B-HT 920 was almost equipotent with noradrenaline to inhibit the electrically induced contractions. In these tissues, B-HT 920 also displayed almost the same maximal effect as noradrenaline. Clonidine also inhibited the contractions in ileum and trachea; the drug was slightly more potent than noradrenaline. However, in contrast to the intrinsic activity of B-HT 920 that of clonidine was only submaximal. In vas deferens both B-HT 920 and clonidine induced inhibition of contractions on electrical field stimulation at low concentrations. In this organ, both drugs were capable of inducing complete inhibition of the contractile response. In aorta B-HT 920 as well as clonidine were only weak agonists in comparison to noradrenaline. The α₂-blocker, yohimbine, completely blocked the effect of B-HT 920 in ileum at low concentrations (1 × 10^?7 M). Remarkably, however, the inhibitory action of B-HT 920 in trachea was only marginally affected even by high concentrations of yohimbine (1 × 10^?6 M). It is suggested from the present results that B-HT 920 can induce inhibition of both cholinergic and adrenergic neurotransmission presumably by inducing selective stimulation of prejunctional α₂-receptors. In fact, the selectivity of B-HT 920 seems to be comparable to that of clonidine for the α₂-receptor. However, the mode of action of B-HT 920 in trachea may be somewhat uncertain since its effect was not inhibited by yohimbine.     

输精管金属环可复性节育术的酶细胞化学研究及电镜观察

用酶细胞化学方法结合超微结构，观察了家兔输精管经金属环夹及加不同性质支撑物后输精管碱性磷酸酶（ＡＫＰ），睾丸乳酸脱氢酶（ＬＤＨ）的活性变化及输精管、睾丸和附睾的超微结构改变，在细胞学基础上，探讨了输精管金属环可复性节育术的影响因素，并结合酶活性变化，分析了其复通后复孕率较低的原因。     

抗精子抗体对输精管吻合术后生育力的影响

检测了输精管吻合术后４４例的精液常规、性激素、血清和精浆中抗精子抗体。结果表明，未生育组的血清和精浆中抗精子抗体的浓度明显高于生育组，提示血清精浆中抗精子抗体可降低吻合术后患者的夏育能力，吻合术并不能使抗精子抗体消失，吻合术前后应检测抗精子抗体。     

Noradrenergic supersensitivity in the rat vas deferens during barbital withdrawal

Three days' withdrawal from long-term barbital administration results in a shift to the left and increase in the maximum response of the concentration--effect curve to norepinephrine in the isolated rat vas deferens. The maximum response to carbachol and potassium was also increased without a leftward displacement of the concentration--effect curves. This specific increase in sensitivity to norpinephrine could indicate an adaptive alteration of the adrenoreceptors of the rat vas deferens (receptor supersentivity) as has been proposed for supersensitivity in the central nervous system during withdrawal from neuroleptics and barbiturates.     

Influence of Long and Short Photoperiods on the Morphology and Androgen Receptor Levels of the Epididymis and the Ductus Deferens of Phodopus sungorus/Einfluß langer und kurzer Photoperioden auf die Morphologie und den Androgen-Rezeptor-Gehalt des Nebenhodens und des Ductus deferens von Phodopus sungorus

Summary: The photoperiodic influence (LD 16:8 long photoperiod, LD 8:16 short photoperiod) on the morphology and the androgen receptor level of the epididymis and the ductus deferens of Phodopus sungorus was investigated. Under short day-conditions, the wet weight of the epididymis is reduced to 5–6%, the diameter of the epididymal duct and of its lumen are reduced, the heigth of the epithelium and the thickness of the smooth muscle layer are increased. Number and size of epithelial and smooth muscle cells are not changed, no atrophy of the smooth muscle cells is found. The loss in wet weight during short photoperiods is discussed in relation to the loss of stored sperm and luminal fluid. The wet weight of the ductus deferens is decreased to about 30% at short photoperiods, the total length of the organ, its diameter and the luminal diameter are decreased. The height of the epithelium is slightly, and the thickness of the smooth muscle layer is strongly, reduced, the latter due to an enormous atrophy of the smooth muscle cells. The androgen receptor content of the epididymis (per pair of organs) is reduced to about 5%, that of the ductus deferens to about 10% of the values found at long photoperiods, indicating a significant loss of androgen receptors with low circulating androgen levels. Zusammenfassung: Der Einfluß langer (LD 16:8) und kurzer (LD 8:16) Photoperioden auf die Morphologie und den Androgen-Rezeptor-Gehalt des Nebenhodens und Ductus deferens von Phodopus sungorus wurde untersucht. Bei Kurztagbedingungen verringert sich das Feuchtgewicht des Nebenhodens auf 5–6%, der Durchmesser des Nebenhodengangs und seines Lumens gehen zurück, während die Höhe des Epithels leicht und die Dicke der glatten Muskelzellschicht deutlich zunehmen. Zahl und Größe der Epithel- und glatten Muskelzellen bleiben unverändert; es zeigt sich keine Atrophie der glatten Muskelzellen. Der Verlust an Feuchtgewicht bei kurzen Photoperioden wird hauptsächlich auf den Verlust von gespeicherten Spermien und Samenflüssigkeit zurückgeführt. Das Feuchtgewicht des Ductus deferens geht bei kurzen Photoperioden auf 30% zurück, es verringern sich die Gesamtlänge des Organs, sein Durchmesser und der des Lumens. Die Höhe des Epithels geht leicht, die Dicke der glatten Muskelzellschicht deutlich zurück; letzteres ist auf die starke Atrophie der glatten Muskelzellen zurückzuführen. Der Androgen-Rezeptor-Gehalt (pro Organpaar) ist beim Nebenhoden auf etwa 5% der Werte bei Langtagbedingungen und beim Ductus deferens auf etwa 10% reduziert. Damit ergibt sich ein signifikanter Verlust von Androgen-Rezeptoren bei niedrigem Androgen-Gehalt im Serum.     

Fast and slowly inactivating components of Ca-channel current and their sensitivities to nicardipine in isolated smooth muscle cells from rat vas deferens

(1) Fast and slowly inactivating components of Ca-channel current were compared to clarify whether more than one type of Ca-channel exists in smooth muscle cells from rat vas deferens using the whole cell variant of the patch clamp technique. The pipette was filled with 150 mM Cs solution to eliminate outward current and Ba was used as the charge carrier for Ca-channel current. (2) When activated by a 5 s test pulse to 0 mV from a holding potential of −60 mV, the inactivation process of Ba-current was well fitted by the sum of two exponentials. The time constant of the faster inactivating component was 100–300 ms and that of the slower inactivating component was 1.5–3 s. Steadystate inactivation curves of the fast- and slow-components were very similar. (3) The inward current activated at 0 mV from −80 mV was inactivated faster than that from −30 mV. The voltage-dependencies of the peak current from holding potentials of −30 mV and −80 mV were similar. Both had voltage threshold at −30 mV and were maximal at +10 mV. (4) Low concentrations of nicardipine (10⁻⁹ to 10⁻⁷ M) preferentially inhibited the slow component while higher concentration (10⁻⁶ to 10⁻⁵ M) were required to block the fast component. The current activated from a holding potential of −30 mV was almost fully suppressed by 10⁻⁷ M nicardipine whereas that from −80 mV was blocked only slightly. The voltage dependencies of the peak currents before and during the superfusion with nicardipine (10⁻⁷ M) were similar although the peak amplitude was suppressed in the presence of the drug. (5) These results suggest that the existence of either (a) two populations of Ca channels that differ in the time course of inactivation and the sensitivity to nicardipine, but have nearly identical dependence on membrane potential or (b) one population of Ca channel having two different states of inactivation and the sensitivity of nicardipine, in rat vas deferens.     

Centrally induced reduction in sympathetic tone — A postsynaptic α-adrenoceptor-stimulating action of imidazolines

Naphazoline or oxymetazoline (both 30 μg/kg) were injected into the cisterna magna of anaesthetized cats and reduced blood pressure, heart rate and the electrical discharge rate of small fibre bundles of the preganglionic sympathetic splanchnic nerve. Cats were depleted of endogenous noradrenaline by pretreatment with reserpine (5 mg/kg, 18 h) and α-methyl-p-tyrosine) twice 300 mg/kg, 18 and 2 h). In these animals, intracisternal injection of 30 μg/kg oxymetazoline exerted a decrease of sympathetic discharges similar to that described for non-pretreated animals. In noradrenaline-depleted cats intracisternal injection of 1 μg/kg clonidine also decreased the sympathetic discharges. It is concluded that these imidazolines exert their sympathoinhibitory and cardiovascular effects by stimulation of postsynaptic α-adrenoceptors in the CNS.In the isolated rat vas deferens, oxymetazoline was a much weaker agonist (intrinsic activity (i.a.) < 0.1) than naphazoline and clonidine (i.a. 0.6 or 0.8 respectively). All three imidazolines exerted considerable competitive antagonism against noradrenaline, with oxymetazoline being the most potent antagonist (pA₂: 6.0; clonidine 5.0; naphazoline 5.5). The order of agonistic activities of the three imidazolines on the vas deferens is different from that on other peripheral adrenergic systems and indicates different α-adrenoceptors. The possibility of receptor differences in the CNS is discussed.     

The influence of catecholamines and serotonin on histamine uptake and metabolism by guinea pig atrium.

The influence of serotonin and catecholamines on the uptake and metabolism of 14C-histamine by isolated guinea pig atrium has been investigated. Epinephrine, norepinephrine and serotonin were found to reduce the histamine uptake and the formation of methylhistamine, in a dose-dependent fashion. The order of potency was epinephrine greater than norepinephrine greater than serotonin. Aliphatic diamines, such as spermine, do not affect the accumulation and metabolism of histamine. It is suggested that serotonin and catecholamines, may enhance histamine responses by decreasing the uptake and metabolism of this amine.