PROLONGED EFFECTS OF p‐CHLOROPHENYLALANINE ON THE BLOOD PRESSURE OF CONSCIOUS NORMOTENSIVE AND DOCA/SALINE HYPERTENSIVE RATS

Abstract

1 In deoxycorticosterone acetate (DOCA) saline hypertensive rats a single dose of p-chlorophenylalanine methylester (PCPAME) (400 mg/kg i.p.) produced a significant fall in blood pressure (20–43 mmHg) which lasted for at least 8 days and was accompanied by a parallel depletion of brain stem 5-hydroxytryptamine (5-HT) but not of noradrenaline (NA). 2 In normotensive rats single doses of PCPAME (200 and 400 mg/kg i.p.) produced a significant hypotension (15–20 mmHg) after a latent period of 5 days. An initial pressor response (12 mmHg) was observed at the higher dose level only on day 3. 3 The hypotensive response to PCPAME (200 mg/kg i.p.) in normotensive rats was not modified by pretreatment with 5,6-dihydroxytryptamine (5,6-DHT; 50 μg i.c.v.) or 6-hydroxydopamine (6-OHDA; 3 × 250 μg intracerebroventricularly). 4 It is concluded that the hypotensive response to PCPAME in normotensive rats is independent of brain stem depletion of 5-HT and is probably not mediated by the formation of a false transmitter substance acting via central noradrenergic inhibitory pathways. The mechanism involved in the antihypertensive response to PCPAME in DOCA/saline hypertensive rats has yet to be defined.