No abstract

In STZ-diabetic rats, the distribution volume of morphine increased, the glucuronidation rate and M3G transportation into the blood were enhanced, and the excretion of M3G was decreased, leading to an increase in the plasma M3G concentration.

The radula protractor can be made to be spontaneously rhythmic, although it is normally a quiescent, phasic muscle, with apparently multi-unit organization. Acetylcholine and potassium depolarize with contracture. Once a radula muscle has been put into a long-lasting contracture by acetylcholine, tryptamine can repolarize it with accompanying relaxation. In the continued presence of acetylcholine and tryptamine, the repolarization and relaxation gradually taper off while membrane oscillation accompanied by mechanical rhythmicity develops. Contrariwise, if a radula protractor is in a potassium contracture, tryptamine will potentiate the contracture without affecting the level of membrane depolarization. Potentiation of potassium contracture, without changing potential level, can also be effected by increased calcium concentrations or by caffeine. After a muscle has been soaked in artscial sea water lacking calcium, its twitch tension, tetanic tension, potassium contracture, and acetylcholine contracture become directly dependent on external calcium concentration.

Adenylate cyclase activity was demonstrated in the cilia, dendritic knob and axon of rat olfactory cells by using a strontium-based cytochemical method. The activity in the cilia and the dendritic knob was enhanced by non-hydrolyzable GTP (guanosine triphosphate) analogues and forskolin, and inhibited by Ca2+, all in agreement with biochemical reports of the odorant-sensitive adenylate cyclase. The results support the hypothesis of cyclic AMP working as a second messenger in olfactory transduction and imply that the transduction sites exist not only in the olfactory cilia but also in the dendritic knob. Enzymatic activity was also observed in the olfactory dendritic shaft by treating the tissue with 0.0002% Triton X-100, although the properties and role of the enzyme in this region are uncertain. The detergent inhibited the enzymatic activity in the cilia and the dendritic knob.

Guanylyl cyclase activity was cytochemically demonstrated in rabbit foliate taste buds. The enzymatic activity was localized in the apical portion (microvilli and neck) of taste bud cells. Especially strong activity was observed on the microvillous membrane of type I (dark) cells and often on a blunt process of type III cells. The microvilli of type II (light) cells showed weak enzymatic activity. Considering that the apical portion of taste cells is a likely site of interaction between taste stimuli and the cells, the results support the idea that cyclic GMP is involved in taste transduction.