Barrel rotation in rats induced by intracerebroventricular bradykinin antagonists

Cardiovascular effects of brain kinin receptor blockade in spontaneously hypertensive rats

We studied the role of brain kinins in the regulation of cardiovascular function. Intracerebroventricular injection of 380 pmol bradykinin increased mean blood pressure by 20 +/- 2 mm Hg (P < .01) in normotensive Wistar-Kyoto (WKY) rats. Complete inhibition of this effect was achieved with intracerebroventricular administration of the newly synthesized, long-acting B2 receptor antagonist D-Arg,[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin (Hoe 140). On a molar basis, Hoe 140 was two orders of magnitude more potent than antagonists of the first generation. Baroreceptor sensitivity, estimated as the heart rate response to blood pressure changes induced by intravenous injection of phenylephrine or sodium nitroprusside, was not altered by Hoe 140 in WKY rats. In spontaneously hypertensive rats (SHR), baroreceptor reflex sensitivity to increments in mean blood pressure was reduced by Hoe 140 (mean slope value: -0.47 +/- 0.07 versus -0.92 +/- 0.13 beats per minute per millimeter of mercury in controls, P < .05). Hoe 140 did not affect the tachycardic component of the baroreceptor reflex. Two-week intracerebroventricular infusion of Hoe 140 did not alter systolic blood pressure or heart rate in WKY rats. In SHR, systolic blood pressure increased (P < .01) similarly during the infusion of Hoe 140 or vehicle (from 174 +/- 6 to 220 +/- 5 mm Hg and 178 +/- 4 to 210 +/- 4 mm Hg at 2 weeks, respectively), whereas heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged analgesia after intracerebroventricular Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2)

A peptide recently isolated from human and bovine brain, Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2), was tested for its effects on nociception in the tail-flick test after intracerebroventricular injection in the rat. Tail-flick latencies were significantly increased with a rapid onset and remained significantly elevated for at least 50 min. Naloxone reversed the effect of the peptide, indicating opiate receptor involvement in the response. Met-enkephalin at the same dose produced only slight antinociception. Some animals showed 'barrel-rolling' behavior in addition to the analgesia; this behavior was unusually short-lived, not a prerequisite for the analgesia, and had no apparent persistent effects. The results show that, in addition to previously described opiate-like actions (binding to the mu-receptor and inhibition of electrically induced contractions of the guinea pig ileum), Tyr-W-MIF-1 is capable of inducing significant analgesia.

Barrel rotation in rats induced by SMS 201-995: suppression by ceruletide

Intracerebroventricular administration of SMS 201-995 (5 micrograms/rat), a somatostatin analogue, induced barrel rotation in rats. Pretreatment with ceruletide (40 micrograms/100 g b. wt., IP) 3 days or 7 days prior to the injection of SMS 201-995 significantly inhibited the response rate of barrel rotation induced by SMS 201-995, but not that induced by arginine-vasopressin (1 microgram/rat, ICV). The suppressive effect of ceruletide on barrel rotation could be partially countered by MK-329, a selective peripheral CCK (CCK-A) receptor antagonist. Desulfated cerulein did not affect the barrel rotation induced by SMS 201-995. These findings suggest that ceruletide specifically suppresses the barrel rotation evoked by SMS 201-995 in a long-lasting manner possibly acting through CCK-A receptor.

Brain neuropeptides: actions on central cardiovascular control mechanisms

The many peptides we have not considered (e.g. gastrin, motilin, FMRFamide, carnosine, litorin, dermorphin, casomorphin, eledoisin, prolactin, growth hormone, neuromedin U, proctolin, etc.) were omitted due to lack of information as far as any putative central cardiovascular effects are concerned. However, even for some of these peptide pariahs intriguing snippets of information are available now (e.g. ref. 85), although as we write, the list of possible candidates for investigation grows longer. On an optimistic note, it is becoming clear that many brain neuropeptides may have important effects on cardiovascular regulation. It seems feasible that 'chemically coded' pathways in the brain might be the neuroanatomical correlate of a 'viscerotopic' organization of cardiovascular control mechanisms, whereby the activity of the heart and flows through vascular beds are individually controlled, but in an integrated fashion, utilizing particular combinations of neurotransmitters and neuropeptides within the brain. Such possibilities can only be investigated, properly, by measurement of changes in cardiac output and regional haemodynamics in response to appropriate interventions, in conscious, unrestrained animals.

Effects on blood pressure of intracerebroventricular administration of a kinin antagonist

The components of the kallikrein kinin system are present in brain, and blood pressure is increased when kinins are injected into the brain cerebral ventricles. Therefore, brain kinins may play a role in the regulation of blood pressure. Kinin analogs which are effective as blockers of the vasodilatory and musculotropic activity of kinins have recently become available. Our objective in this study was to examine whether one of these kinin antagonists (K-ant) inhibits the pressor activity of intracerebroventricular (ICV) bradykinin, and whether ICV injections of this antagonist would alter basal mean blood pressure (BP). The analog used was DArg0-Hyp3-Thi5,8-DPhe7-bradykinin. All injections (10 microliters) were made into a lateral cerebral ventricle of restrained, conscious rats. The hypertensive response to 0.5 microgram bradykinin was partially blocked by simultaneous injections of either 5 or 10 micrograms of the K-ant: From (delta MBP = 36 +/- 7 to 17 +/- 5, p less than 0.05, and from 34 +/- 6 to 8 +/- 1 mmHg, p less than 0.01, respectively. Lower concentrations of K-ant were ineffective; the K-ant at doses up to 10 micrograms had no effect on BP. Doses of 25 and 50 micrograms increased BP (delta MBP = 32.5 +/- 5 and 59.0 +/- 5.5 mmHg, respectively, p less than 0.001). Both the 25 and the 50 micrograms doses of the K-ant induced barrel rotation in all rats. These data suggest that kinins present in circumventricular structures do not play a role in normal blood pressure regulation.(ABSTRACT TRUNCATED AT 250 WORDS)