Effects of humoral modulators and naloxone on morphine-induced changes in the spontaneous locomotor activity of the rat

The s.c. administration of 20 mg/kg of morphine-HCl produced a decrease in the spontaneous locomotor activity (SLMA) of rats. The decrease in SLMA was significantly antagonized by p-chlorophenylalanine (p-CPA). When rats pretreated with p-CPA were given 5-hydroxytryptophan before morphine injection, the marked sedative response to morphine was restored, suggesting that the morphine-induced decrease in SLMA of rats may depend on the release of 5-hydroxytryptamine by morphine. By contrast, the s.c. administration of 5 mg/kg of morphine-HCl produced a significant increase in SLMA of rats. The magnitude of the increase was reduced by atropine, scopolamine or alpha-methyl-p-tyrosine. It appears that both adrenergic and cholinergic mechanisms participate in the increase in SLMA of rats induced by morphine. Both the increase in SLMA produced by 5 mg/kg of morphine and the decrease in SLMA induced by 20 mg/kg of morphine were completely antagonized by the s.c. administration of naloxone-HCl, 0.0625 and 0.25 mg/kg, respectively. Thus, it appears that the receptor with which morphine interacts to produce stimulation is chemically identical with or very similar to the receptor with which morphine combines to induce depression. The former receptors, however, are likely to be located on different neurons from the latter.

The effect of p-chlorophenylalanine on the pethidine- or methadone-induced decrease in locomotor activity of rats

Either pethidine HCl (50 mg/kg s.c.) or methadone HCl (8 mg/kg s.c.) produced a prominent decrease in locomotor activity of rats. Pretreatment of rats with p-chlorophenylalanine (p-CPA, 320 mg/kg i.p.) 48 h before the narcotic injection significantly antagonized the activity-decreasing effects of narcotics. When rats pretreated with p-CPA were given 5-hydroxytryptophan (75 mg/kg s.c.) 30 min before narcotic administration, the activity-decreasing response to narcotics was restored. Thus, a decrease in locomotor activity induced in rats by either pethidine or methadone is probably mediated by serotonergic mechanisms.

Polyamine transport and metabolism in mouse mammary gland. General properties and hormonal regulation

Mouse mammary gland has been shown to possess a transport system for spermidine, spermine, and putrescine. The uptake system for sperimidine, as studied in detail on mammary explants in culture is a time-dependent, energy-requiring process which can be stimulated by insulin and prolactin. The stimulatory effect of insulin involves both enhancement of Vmax for spermidine influx and prevention of efflux of the polyamine, whereas prolactin, in the presence of insulin, elicits a greater increase in Vmax for spermidine. Studies are also reported on the effects of temperature, concentration, and various inhibitors on this system. The accumulated spermidine exists virtually in an unchanged form with little metabolic conversion to either spermine or putrescine or to its conjugated form. In contrast, spermine and putrescine, both of which are also taken up by mammary explants, undergo metabolic conversion to spermidine.

Studies on regulatory factors of ornithine decarboxylase activity during development of mouse mammary epithelium in vitro

The activity of ornithine decarboxylase increases markedly in a biphasic manner during the hormone-dependent development of mouse mammary epithelium in vitro. The first peak of activity occurring at 3 to 4 hours of culture was elicited by incubating mammary explants in a culture medium without any added hormones, although addition of insulin or prolactin, or both, caused a greater increase. The emergence of the second peak of activity at about 12 hours depended on the actions of both insulin and prolactin. A second increase in activity could also be effected postmitotically by the delayed addition of prolactin. Studies with actinomycin D and cycloheximide suggest that the first increase in enzyme activity may be effected at a post-transcriptional level, whereas a second increase may be at both transcriptional and translational levels. During the first 3 hours of incubation, there was a rapid, transient increase in cyclic AMP concentration in mammary epithelium. The presence of insulin or prolactin in culture did not affect the change in epithelial cyclic AMP concentration. Addition of several derivatives of cyclic AMP, 0.1 to 0.5 mM, as well as prostaglandin E1, a stimulator of adenylate cyclase, resulted in enhancement of the first increase in enzyme activity. The effect of cyclic nucleotide was additive to that of insulin and prolactin and appears to be mediated at a post-transcriptional level. The stimulatory effect of a lower concentration of both the cyclic nucleotide and prostaglandin E1 was augmented by theophylline, an inhibitor of phosphodiesterase. These results may suggest possible involvement of cyclic AMP in the first increase in enzyme activity that occurs in the absence of any added hormones.

Insulin-unresponsive tissues respond to superactive insulin-like material

Insulin-like material prepared from insulin-Sepharose stimulates glucose oxidation by isolated diaphragm of C57Bl/6J ob/ob mice, but insulin does not. This material is much more effective than insulin on epididymal fat tissue from these mice. Insulin-like material and insulin are equipotent on the corresponding tissues from lean littermates.

Structure of a soluble super-active insulin is revealed by the nature of the complex between cyanogen-bromide-activated sepharose and amines

Insulin-like material with elevated insulin specific acitivity is released from insulin-Sepharose in the presence of bovine-serum albumin. The mechanism of release and the chemical nature of this insulin-like material are revealed by the finding that amine-Sepharose is O-Sepharose-N-substituted isourea. Nucleophilic attack by amino groups releases N-1-N-2-disubstituted guanidines. Correspondingly, it is shown that the super-active insulin-like material is an N-1-N-2-disubstituted guanidine in which insulin and bovine-serum albumin are the substituents.

Studies on pharmacological and biochemical properties of deamino-dicarba-[GLY-7]-oxytocin (Y-5350)

Pharmacological and biochemical properties were investigated on deamino-dicarba-[Gly-7]-oxytocin (Y-5350). This is a newly developed compound, in which the disulfide bond and [Pro-7] of deamino-oxytocin are substituted by an ethylene linkage and glycine respectively. Bioassayed Y-5350 exhibited 202.6 u/mg of oxytocic activity, 4.6 u/mg of avian depressor activity, 441.2 u/mg of rat milk-ejecting activity and 0.02 u/mg of rat antidiuretic activity, however, adepressor activity was also evident in rats. In particular, the diuration of antidiuretic activity was short. Moreover, the oxytocic activity in pregnant rats and rabbits was weak in comparison with oxytocin. Cumulative dose-response studies were carried out on the isolated rat uterus using van Dyke-Hasting solution. The intrinsic activity was the same level as that of oxytocin, and the pD2 value was 8.62. Oxytocic activity was much enhanced by the existence of 0.5 or 2mM magnesium ion in vitro. However, the agreement between in vivo and in vitro oxytocic activity was not complete when assay was carried out in the prescence of 2 mM magnesium ion. Oxytocin was inactivated by the serum of pregnant women. In the experiment using rats, oxytocin was also destroyed by the extracts of uterus, kidney and liver. In contrast, Y-5350 was not destroyed by any of the enzyme solutions mentioned above.

A soluble super-active form of insulin

Insulin-like material can be extracted from insulin-Sepharose. This soluble material elicits super-insulin responses from mammary epithelial cells. It stimulates the accumulation of alpha-aminoisobutyric acid by virgin mouse mammary cells, which are unresponsive to insulin itself. It exerts a greater stimulatory effect on mammary cells from pregnant mice than insulin. It also is more efficacious than insulin as a stimulant of DNA synthesis and the combined activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and phosphogluconate dehydrogenase (EC 1.1.1.43). Its specific biological activity on these cells is more than five times greater than that of insulin.