Fenibut binding with bicuculline-insensitive GABA receptors in the rat brain

(+/-) Fenibut beta-phenyl-GABA) was not able to displace 3H-GABA in Na+ independent GABA binding (IC50 greater than 250 microM). Nevertheless, (+/-) fenibut and (+/-) baclofen effectively displaced 3H-GABA in Ca2+ dependent GABA binding in the presence of 50 microM (+) bicuculline. (+/-) Fenibut was less potent in this respect. It is suggested that fenibut may act via bicuculline-insensitive GABA receptors.     

Activation of erythrocyte membrane Ca2+-ATPase by calpain

Ca2+-ATPase of erythrocyte membranes, prepared from erythrocytes substantially removed of contaminating leukocytes, was found to be activated by calpain isolated from the same source. Saponin or glycodeoxycholate treatment of membranes was essential for elicitation of the calpain response. Unlike the membrane bound ATPase, solubilized ATPase was inactivated by calpain. Digestion of membranes with the protease did not affect the Km (ATP) of Ca2+-ATPase though stimulation of the membrane ATPase by calmodulin could be partially substituted by calpain treatment. As compared with control, Ca2+-ATPase of calpain-digested membranes attained maximal activity at a lower free Ca2+ concentration.     

An automated technique for monitoring carbon dioxide respired by insects*

ABSTRACT. A non-dispersive infrared gas analyser equipped with a Luft-type sonic detector and flow-through reference cell was automated to monitor the total volume of carbon dioxide (CO₂) respired by single insects or groups of insects. The infrared analyser was interfaced with an integrator for quantification, a microprocessor to control intermittent air flow through the insect respiration chambers, and a microcomputer for data storage and reduction. This technique has been used to monitor the CO₂ Output of diapausing and non-diapausing mature fifth instar larvae and of developing pupae of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The resulting data were accurate, quantitative and reproducible.     

Effects of cholinergic drugs on longitudinal muscle contractions of Fasciola hepatica

Acetylcholine, cholinergic agonists and acetylcholinesterase inhibitors significantly decrease the amplitude and frequency of spontaneous longitudinal muscle contractions in Fasciola hepatica. In order of their effects on the inhibition of muscle contractions, the cholinergic agonists can be ranked as nicotine greater than carbachol greater than acetylcholine. High calcium ion concentration also causes a significant inhibition of contractions. Atropine, a cholinergic antagonist that acts on muscarinic receptors, significantly increases the amplitude and frequency of spontaneous contractions and completely reverses the effects of cholinomimetic drugs, including nicotine. In adult F. hepatica, the levels of acetylcholine and its precursor choline are 3.14 +/- 0.55 and 13.75 +/- 3.72 pmol/mg wet weight, respectively. The activities of choline acetyltransferase, specific acetylcholinesterase and the nonspecific cholinesterase are 1.25 +/- 0.19, 238.0 +/- 13.0, and 83.0 +/- 33.0 nmol/hr/mg protein, respectively.