The central effects of a low-molecular weight fraction of
polyphloretin phosphate (PPP) with molecular weight about 4600 were studied using several behavioural tests in animals (Lat's test, open-field test, hold-board test, irritability, spontaneous motor activity),
chlorpromazine-induced
catalepsy test, body temperature measurements,
hexobarbital-induced sleep duration, reaction to thermal painful stimulus, measurements of arterial blood pressure, heart rate and respiratory rate. The activity of
prostaglandin synthetase was determined also in the microsomes of bovine hypothalamic cells in vitro. Using some of the above tests the effect of PPP was studied on the central action of
prostaglandins F2 alpha and E2 (
PGF2 alpha and
PGE2). PPP was administered intraventricularly (i.c.v.) in various doses (doses producing the lowest pharmacological effect in a given test) 10 minutes before i.c.v. administration of these
prostaglandins in doses of 1 or 10 microgram. It was shown that PPP (low-molecular weight fraction) injected into the lateral cerebral ventricle of the rat exerted a
biological effect on the central nervous system manifesting itself as behaviour changes in the tests used, and as changes of the arterial blood pressure. PPP i.c.v. antagonized certain central effects of
PGF2 alpha and
PGE2. The degree of inhibition of various
prostaglandins differed in relation to the test used and was somewhat stronger in the case of
PGF2 alpha.