G. Pagnini

HISTAMINE‐SENSITIVE ADENYLATE CYCLASE IN HYPOTHALAMUS OF RAT BRAIN: H1 AND H2 RECEPTORS

Abstract— In in vitro experiments on rat hypothalamic homogenates the effects of biogenic amines such as histamine (HA), noradrenaline (NA), dopamine (DA), serotonin (5‐HT) and drugs such as isoprenaline (ISP), 2‐(2‐pyridyl)ethylamine (H2 stimulant—Hls), 4‐methyl‐histamine (H2 stimulant H2s), mepyramine (H1 antagonistp Hla), cimetidine (H2 antagonist—H2a) were tested on adenylate cyclase activity. HA possessed a powerful stimulating effect on hypothalamic adenylate cyclase activity, higher than that shown by the other substances.

Effects of bromocriptine on adenylate cyclase and phosphodiesterase activities of rat striatum.

The activity of 2‐bromo‐α‐ergokryptine (bromocriptine) (5 mg kg−1, i.p.) on adenylate cyclase and on phosphodiesterase (PDE I‐PDE II) of rat striatum, has been examined both in vitro and in vivo. In vitro and in vivo bromocriptine stimulated adenylate cyclase activity, but reduced the stimulating effect of dopamine on adenylate cyclase activity. Bromocriptine showed a dose‐dependent biphasic action on phosphodiesterases in vitro while in vivo it stimulated them. The results obtained proved bromocriptine to have an agonist‐antagonist action at striatal dopamine receptor level, with a relevant effect on the cAMP system.

Enhancement of pentobarbital narcosis by drugs competing on the serum protein binding

Abstract Prior subcutaneous administration of sulfaethylthiazole (SET), sulfamethazine (SMZ), sulfanilamide (SNA), salicylic acid (SA), doxycycline (DOXI), p -amino-salicylic acid (PAS) is able to enhance the intraperitoneal pentobarbital (PB) narcosis in mice. Such narcosis enhancement seems to be connected with competition between these drugs and PB for serum proteins, which results in an increase of the unbound PB and consequently a higher PB cerebral concentration. This higher concentration may be attributed to competition for serum protein binding, since the PB metabolism is unaffected by SET, SMZ, SNA, SA, DOXI and PAS.

The effect of age and sex on the expression of prolactin binding activity in the chicken bursa of fabricius

The binding of 125I-labeled prolactin (PRL) to membranes from the bursa of Fabricius of male and female chicks of different ages (15-30-45 and 60 days) was studied. In male chicks the binding was very low in 15 day-old animals and slightly increased in more aged animals. In female chicks the binding was more evident in young animals and decreased in 60 day-old animals. The binding showed a hormonal specificity and Scatchard analysis of the binding revealed the presence of binding sites with low capacity and high affinity. The presence of PRL receptors in the bursa of the chick, a structure that confers immunological competence to birds, gives further support to the involvement of the hormone in the immune processes.