The ␥-aminobutyric acid type A (GABA A ) receptor is the predominant Cl ؊ channel protein mediating inhibition in the olfactory bulb and elsewhere in the mammalian brain. The olfactory bulb is rich in neurons containing both GABA and dopamine. Dopamine D1 and D2 receptors are also highly expressed in this brain region with a distinct and complementary distribution pattern. This distribution suggests that dopamine may control the GABAergic inhibitory processing of odor signals, possibly via different signaltransduction mechanisms. We have observed that GABA A receptors in the rat olfactory bulb are differentially modulated by dopamine in a cell-specific manner. Dopamine reduced the currents through GABA-gated Cl-channels in the interneurons, presumably granule cells. This action was mediated via D1 receptors and involved

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Injection of M dopamine or M dibutyryl cyclic AMP (dbcAMP) into intact Carcznus maenas significantly increased influx of sodium from 100% sea water. Injection of pericardial organ (PO) extract, which contains dopamine, also increased influx of sodium. Animals injected with dopamine or PO extract and gills treated with dbcAMP in vitro showed increased NaiK-ATPase activity in the microsomal fraction of the gills. These results suggest a mechanism for short-term activation of Na/K-ATPase when crabs are transferred to a dilute medium.

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Of 116 chitinolytic actinomycetes, previously isolated from marine sediments, 85 were found to possess antimicrobial activity. A high correlation was noted between chitinolysis and bioactivity. A majority of them suppressed the growth of Gram-positive bacteria but only a few inhibited Gram-negative strains and almost one-half of them exhibited antimycotic activity. Several of the last group yielded polyenes of which heptaenes were the most commonly occurring ones. Other strains synthesized detectable amounts of fl-lactam antibiotics. It is suggested that chitinolysis may serve as an indicator of potential bioactivity among marine actinomycetes.tinomycetes to hydrolyze chitin (Hsu and Lockwood 1975). Based on this observation, we recently surveyed our collection of marine actinomycetes for chitinolytic activity and found that many of the strains share this property. Consequently, part of our collection has been divided into an easily definable cluster based on a common secretory property, namely the elaboration of chitinases.In the present investigation, we have attempted to ascertain if chitinolytic activity may be related to the synthesis of antimicrobial substances. Toward this end, 116 chitinolytic strains were grown in submerged culture and analyzed for the production of antibacterial a n d / o r antifungal compounds.