strychnine and hypotaurine

To understand the action and mechanism of hypotaurine, an immediate precursor of taurine, on orofacial nociceptive processing, we examined the direct effects and receptor types involved in hypotaurine-induced responses using the whole-cell patch clamp technique in the substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) of immature mice. Under the condition of high-chloride pipette solution, hypotaurine elicited inward currents or upward deflections of membrane potential, which increased in a concentration-dependent manner (30-3000 μM) with the EC

Topics: Animals; GABA-A Receptor Antagonists; Membrane Potentials; Mice; Neurons; Patch-Clamp Techniques; Pyridazines; Receptors, GABA-A; Receptors, Glycine; Strychnine; Substantia Gelatinosa; Synaptic Potentials; Taurine; Trigeminal Nuclei

Concentrations ranging from 0.1 nM to 30 microM of the aminoacids l-alanine (l-ALA), taurine, hypotaurine and beta-ALA were assayed on the chronotropic responses of rat isolated atria stimulated through their cardioaccelerans nerves. The increases in atrial rate obtained in frequency-response curves to nerve stimulation (0.1-12.8 Hz) were not modified by taurine, hypotaurine and beta-ALA but were reduced by l-ALA (0.01 and 0.1 microM). L-ALA did not modify the chronotropic responses to exogenous norepinephrine (NE). In the atria labeled in vitro with [3H]NE, the release of radioactivity evoked by postganglionic nerve stimulation at 2 Hz (6 V, 0.5 msec duration for 2 min) was reduced to 70% of control values by 0.1 microM l-ALA. The release of [3H]NE evoked by 60 and 100 mM KCl was also reduced by 0.1 microM l-ALA to 40 and to 70% of control values, respectively. L-ALA (0.1 microM) did not affect the outflow of tritium provoked by a 1-min incubation with 1 microM tyramine. The chronotropic responses to nerve stimulation were not modified by the l-ALA metabolites pyruvate and glutamate but were reduced by an analog of l-ALA, alpha-(methylamino)-isobutyric acid, which also diminished the release of [3H]NE elicited by nerve stimulation at 2 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alanine; Animals; beta-Alanine; Bicuculline; Dose-Response Relationship, Drug; Female; Heart Atria; Heart Rate; Male; Norepinephrine; Potassium Chloride; Rats; Strychnine; Sympathetic Nervous System; Synaptic Transmission; Taurine

The effects of the possible metabolites of taurine--taurocyamine and hypotaurine--and of homotaurine on spike discharge frequency of guinea pig cerebellar Purkinje cells were investigated in comparison with taurine and GABA. Taurocyamine, hypotaurine and homotaurine all dose-dependently suppressed the spike frequency with potencies relative to taurine (ED50 = 1.0 mM) of 6, 0.5 and 500, respectively. Both picrotoxin and strychnine competitively blocked the inhibition by all the substances tested, except for the non-competitive antagonism by picrotoxin on taurocyamine. The sites sensitive to taurocyamine and hypotaurine were situated primarily in the dendritic region of the cerebellar molecular layer, while those to homotaurine were primarily near the Purkinje cell soma. The onset of the inhibitory action of taurine and related sulfur-containing substances was found to be slower than that of GABA.

Topics: Animals; Cerebellum; Culture Techniques; Evoked Potentials; gamma-Aminobutyric Acid; Guanidines; Guinea Pigs; Interneurons; Neural Inhibition; Picrotoxin; Purkinje Cells; Strychnine; Taurine