The effect of DOPA on segmental reflexes in rat pups]

In acute experiments on spinal 5-30-day rat puppies, studies have been made of the effect of DOPA (100 mg/kg intraperitoneally) on monosynaptic reflex in extensors (evaluated by parameters of H-reflex) as well as on polysynaptic segmentary reflexes. In 5-7-day animals, mainly the inhibitory effect was observed with a short phase of facilitation of monosynaptic reflex. From the 10th day, facilitatory effect of DOPA becomes a predominant one reaching maximum to the 16th day. Within first 16 days of postnatal life, DOPA exhibits facilitatory effect on short-latent polysynaptic reflexes and inhibits long-latent ones. To the 30th day, reactions which are typical of adult animals are observed: inhibition of short-latent and facilitation of long-latent polysynaptic discharges. The data obtained indicate that in early postnatal development the effect of DOPA on mono- and polysynaptic reflexes qualitatively differs from that in adult animals.     

Aspirin and the reversal of antifertility effect of iproniazid in rats

Iproniazid, a specific monoamine oxidase inhibitor which is known to exert its primary influence by interfering in the metabolism of catecholamines, showed its antifertility efficacy by causing luteolysis in rats. A concomitant regimen of iproniazid and aspirin, a very potent inhibitor of prostaglandin biosynthesis and release, consistently prevented the iproniazid-induced luteolysis and embryonic resorption in the test animals. It has been proposed that iproniazid-induced luteolysis in rats is probably mediated through an increased production of endogenous prostaglandins as a result of an abnormally higher concentration of catecholamines both at central and peripheral levels.     

The effect of reserpine on the pars intermedia of the rat pituitary

Summary Reserpine has a stimulatory effect on the pars intermedia of the rat pituitary, probably mediated by its action on regulatory catecholaminergic nerves. The effect of single intraperitoneal injections of 0.1–20 mg/kg b.w. of reserpine was studied in adult male rats. Reserpine at a dose of 2 mg/kg b.w. induced degranulation, orientation of the secretory granules along the cell membrane and loss of formaldehyde-chloral-induced fluorescence, accompanied by an activation of the granular endoplasmic reticulum and the Golgi apparatus. With higher doses progressive degranulation and loss of fluorescence were observed. The effect was, however, heterogeneous, and with all doses cells displaying normal ultrastructure and normal fluorescence were regularly present.To study the release of granular products (containing a different components of the pro-opiomelanocortin chain) from individual cells, formaldehyde-chloral induced fluorescence and -MSH- and -endorphin immunoreactivies were demonstrated in consecutive sections from pituitaries of rats given 8 mg/kg body weight of reserpine 24 h before sacrifice. The results indicate coordinated release of these granular products at the cellular level after reserpine treatment.This work was supported by Finska Läkaresällskapet     

The possible mode of action of iproniazid. I. Differential luteolytic effect of iproniazid before and after the establishment of placental adolescence.

Iproniazid, a very specific monoamine oxidase inhibitor, at a dose level of 200 mg/kg body weight induced luteolysis and caused lysis of deciduomata as well as resorption of the established embryos. Exogenous replacement of prolactin, a most consistent stimulant of the endocrine functioning of corpus luteum, or progesterone absolutely reversed the adversity developed following iproniazid injection. Moreover, failure of iproniazid even at a higher dose level in the deviation of the normal sequence of pregnancy after the establishment of placental adolescence strongly tempting to suggest that iproniazid could only show its luteolytic effect when the hypothalamic-pituitary complex is exclusively involved in the maintennance of pregnancy.     

The effect of iproniazid on biogenic amine levels, elaboration and reproduction of alimentary conditioned reflexes]

A study of the action of iproniaside on alimentary conditioning has shown that even its small doses (25 mg/kg) disturb the formation of the conditioned reaction, while large doses (200-250 mg/kg) do not disturb the reproduction of the conditioned reaction elaborated and stabilized before the administration of the drug. Hence, dissociated learning with the use of iproniaside is impossible. The applied doses of iproniaside result in an increased level of biogenic amines in the dopaminergic nigro-neostriate and reticulo-septal brain systems. It is therefore assumed that the effects of iproniaside on learning are due to its influence on the level of the CNS biogenic amines.