Characterisation of the anticholinesterase activity of two new tacrine-huperzine A hybrids.

The effects of two tacrine-huperzine A hybrids, (+/-)-huprine Y and (+/-)-huprine Z, have been evaluated. Bovine and human acetylcholinesterase (AChE) and human butyrylcholinesterase (BChE) inhibition were assayed by Ellman's method. The two huprines were more active than both tacrine and (-)-huperzine A as inhibitors of both human and bovine AChE, and they acted as mixed-type AChE inhibitors.

Presynaptic modulation of K+-evoked [3H]dopamine release in striatal and frontal cortical synaptosomes of normotensive and spontaneous-hypertensive rats.

Regional differences in presynaptic [3H]dopamine ([3H]DA) release and its modulation by D2 DA-receptors between the frontal cortex and striatum obtained from Wystar-Kyoto (WKY) and spontaneous-hypertensive rats (SHR) have been evaluated using superfused synaptosomes. Synaptosomal tritium content was significantly lower in the frontal cortex than in the striatum in both SHR and WKY (approximately 45% and 48%, respectively), but no differences in tritium content were obtained between strains. However, the 15 mM K+-evoked [3H]DA overflow was lower in the SHR as compared to WKY rats in both brain regions (striatum approximately 23%, frontal cortex approximately 21).

Presynaptic effect of 7-OH-DPAT on evoked [3H]-acetylcholine release in rat striatal synaptosomes.

The objective of the present experiments was to study the presynaptic effect of 7-hydroxy-N,N-di-n-propyl-2-aminotetraline (7-OH-DPAT, a D(2)-like dopamine receptor agonist) on [3H]-acetylcholine ([3H]-ACh) release induced by potassium (15 mM, 25 mM and 60 mM), potassium channel-blockers (4-aminopyridine, 4-AP; tetraethylammonium, TEA and quinine) and veratridine to gain insight into the mechanisms involved in the activation of the D(2) dopamine-receptor subtype located at striatal cholinergic nerve terminals. 7-OH-DPAT (1 microM) inhibited the evoked [3H]-ACh release induced by K(+) 15 mM in a similar percentage than that obtained during basal conditions (30% and 27%, respectively). Nevertheless, in the presence of 25 mM and 60 mM of K(+) the inhibitory effect of 7-OH-DPAT was completely abolished.

Synthesis of biosynthetic inhibitors of the sex pheromone of Spodoptera littoralis. Part II: Acetylenic and cyclopropane fatty acids.

The synthesis of new acetylenic and cyclopropane fatty acids, as potential inhibitors of the beta-oxidation step in the proposed biosynthesis of the sex pheromone of the Egyptian armyworm Spodoptera littoralis, is reported. The biological activity of the compounds has been determined by in vitro and in vivo bioassays, and among all the compounds tested, dichlorocyclopropane acid has shown the highest inhibition activity displayed so far.