Preliminary pharmacological screening of Bixa orellana l. leaves

Preliminary pharmacological studies were performed on the methanol extract of Bixa orellana L. (Bixaceae) leaves to investigate neuropharmacological, anticonvulsant, analgesic, antidiarrhoeal activity and effect on gastrointestinal motility. All studies were conducted in mice using doses of 125, 250 and 500 mg/kg of body weight. In the pentobarbitone-induced hypnosis test, the extract statistically reduced the time for the onset of sleep at 500 mg/kg dose and (dose-dependently) increased the total sleeping time at 250 and 500 mg/kg dose. A statistically significant decrease in locomotor activity was observed at all doses in the open-field and hole-cross tests. In the strychnine-induced anticonvulsant test, the extract increased the average survival time of the test animals (statistically significant at 250 and 500 mg/kg). The extract significantly and dose-dependently reduced the writhing reflex in the acetic acid-induced writhing test. Antidiarrhoeal activity was supported by a statistically significant decrease in the total number of stools (including wet stools) in castor oil-induced diarrhoea model. A statistically significant delay in the passage of charcoal meal was observed at 500 mg/kg in the gastrointestinal motility test. The extract was further evaluated in vitro for antioxidant and antibacterial activity. It revealed radical scavenging properties in the DPPH assay (IC50 = 22.36 μg/ml) and antibacterial activity against selected causative agents of diarrhoea and dysentery, including Shigella dysenteriae

Clustering of InsP3 receptors by InsP3 retunes their regulation by InsP3 and Ca2+.

The versatility of Ca2+ signals derives from their spatio-temporal organization. For Ca2+ signals initiated by inositol-1,4,5-trisphosphate (InsP3), this requires local interactions between InsP3 receptors (InsP3Rs) mediated by their rapid stimulation and slower inhibition\ by cytosolic Ca2+. This allows hierarchical recruitment of Ca2+ release events as the InsP3 concentration increases. Single InsP3Rs respond first, then clustered InsP3Rs open together giving a local 'Ca2+ puff', and as puffs become more frequent they ignite regenerative Ca2+ waves. Using nuclear patch-clamp recording, here we demonstrate that InsP3Rs are initially randomly distributed with an estimated separation of 1 m. Low concentrations of InsP3 cause InsP3Rs to aggregate rapidly and reversibly into small clusters of about four closely associated InsP3Rs. At resting cytosolic [Ca2+], clustered InsP3Rs open independently, but with lower open probability, shorter open time, and less InsP3 sensitivity than lone InsP3Rs. Increasing cytosolic [Ca2+] reverses the inhibition caused by clustering, InsP3R gating becomes coupled, and the duration of multiple openings is prolonged. Clustering both exposes InsP3Rs to local Ca2+ rises and increases the effects of Ca2+. Dynamic regulation of clustering by InsP3 retunes InsP3R sensitivity to InsP3 and Ca2+, facilitating hierarchical recruitment of the elementary events that underlie all InsP3-evoked Ca2+ signals