Intracerebroventicular injection of prostaglandin E1 increases γ-aminobutyric acid level in the posterior hypothalamus

The level of γ-aminobutyric acid (GABA) in the posterior hypothalamus, the firing rate of the nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic temperatures (T_IBAT and T_c) were monitored in urethane-anesthetized male Sprague–Dawley rats. These variables were measured before and after an intracerebroventricular injection of 500 ng prostaglandin E₁ (PGE₁). The same variables were monitored in other rats with saline injection. The results showed that PGE₁ caused an increase in GABA concentration, firing rate, T_IBAT, T_c. These findings suggest that GABA-ergic tone in the posterior hypothalamus is important in the control of the sympathetic and thermogenic changes induced by PGE₁.     

Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.