[Ritanserin prolongs the analgesic effect of morphine and slows the development of tolerance]. / Ritanserin prolongiruet anal'geticheskii éffekt morfina i zamedliaet razvitie tolerantnosti.

The effect of 5-HT2 receptor blocker ritanserine on the analgesic effect of morphine was studied in experiments on mice. A single simultaneous injection of ritanserine (10 mg/kg) and morphine (1, 10, and 20 mg/kg) prolonged the duration of analgesia in the tail clip test. Combined subchronic (6 days) injection of morphine and ritanserine (1, 5, and 10 mg/kg) twice a day delayed the development of tolerance to the opiate analgesic effect in the hot plate and tail clip tests.

[The effect of ritanserin on the formation and expression of an opiate abstinence syndrome]. / Vliianie ritanserina na formirovanie i ékspressiiu opiatnogo abstinentnogo sindroma.

The described dependence was formed in mice [correction of rats] by subcutaneous injections of morphine in doses growing from 10 to 100 mg/kg (8 days, twice a day). The effect of 5-HT2 receptor blocker ritanserine (1, 5, and 10 mg/kg) on expression of the abstinence syndrome (according to the behavioral and somato-autonomic parameters) 24 h after morphine discontinuation was studied. Ritanserine attenuated the manifestation of some abstinence parameters associated with activation of the serotonin system in formation of the dependence. The effect was less in expression of abstinence.

[The action of tropic adenohypophyseal hormones when administered intraventricularly on rat behavioral reactions]. / Deistvie tropnykh gormonov adenogipofiza pri ikh vnutrizheludochkovom vvedenii na povedencheskie reaktsii u krys.

In experiments on rats the influence was studied of tropic hormones of adenohypophysis--somatotropin, thyrotropin and adrenocorticotropin (STH, ThTN and ACTH respectively) on the elaboration and extinction of conditioned reaction of active avoidance (CRAA) in Y-maze and behaviour in the open field under microinjections of hormones into the brain lateral ventricle (0.001-0.002 ME). It has been shown that all studied hormones improve animals learning at negative pain reinforcement; ThTH and ACTH retard it in contrast to STH, which accelerates the extinction of the elaborated CRAA; tropic hormones exert differentiated influence on rats behaviour in the open field. No distinct correlation was found between behavioural manifestation and the level of catecholamines in the rats hypothalamus.