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Gonadotropin-releasing hormone (GnRH), which is essential for reproductive function, is made by neurones that migrate from the nasal region into the brain during early embryonic development. This migration begins in chick when the olfactory pit is formed. This is approximately the time that GnRH neurones can be detected immunocytochemically. The present study investigated (i). how early in development the GnRH gene is expressed and (ii). the sites of its expression. Accordingly, reverse transcriptase-polymerase chain reaction (PCR) and in situ hybridization were performed on chick embryos before gastrulation up until the stage by which GnRH neurones have begun to migrate into the central nervous system. Primers were made to the 5'- and 3'-UTR region of the message for cGnRH-I, the form of the peptide that is essential for reproductive function in the chicken. PCR product was found in all stages and the sequences of products from all stages were identical. Thus, the GnRH gene is expressed continuously throughout embryonic development. In situ hybridization with a digoxygenin labelled riboprobe revealed staining along the primitive streak immediately before gastrulation. In later stages, cGnRH-I gene expression was seen in association with the anterior neural ridge. The expression was subsequently restricted to a narrow, clearly defined region, which is associated with the presumptive nasal cavity and olfactory placode. Later, GnRH neurones could be seen in their migratory routes by both in situ hybridization and immunocytochemistry. Expression of the GnRH gene has been described in preimplantation stages in mammals and there is evidence that the neuropeptide plays a role in formation and maintenance of the placenta. What role (if any) it may play in early avian development remains unknown. The demonstration of sites of GnRH expression during the early period of neurulation suggests that GnRH neurones arise before olfactory placode formation.

Tetracyclic guanines have been shown to be potent and selective inhibitors of the cGMP-hydrolyzing enzymes PDE1 and PDE5. In general, these compounds are inactive or only weakly active as inhibitors of PDE3, which is a major isozyme involved in cAMP hydrolysis. Structure-activity relationships are developed at N-1, C-2, N-3, and N-5 on the core nucleus. Compound 31, with an IC50 of 70 pM, is the most potent inhibitor of PDE1, while 50, with an IC50 of 4 nM, is the most potent inhibitor of PDE5. Compounds 20, 22, 30, and 50 are potent dual inhibitors with IC50 values below 30 nM for both PDE1 and PDE5. Compounds 12, 20, and 28 reduced blood pressure by more than 45 mmHg when administered orally at 10 mg/kg to the spontaneously hypertensive rat (SHR).

The L-arginine derived NO-cGMP pathway's role in the response of the arterial wall to balloon catheter injury was examined. Rats were given the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg po twice daily) or vehicle for 6 days before and 2 weeks after balloon catheter injury. NG-nitro-L-arginine methyl ester treatment increased blood pressure and inhibited acetylcholine responses in aortic rings but did not alter the lesions produced by balloon injury. Our results suggest that the L-arginine derived NO-cGMP pathway does not play a significant role in the response of the artery wall to balloon injury in the rat.

SCH 31846, 1-(N-[1(S)-(ethoxycarbonyl)-3-phenylpropyl]-(S)-alanyl)-cis, syn-octahydro-(H-indole-2-S)-carboxylic acid; CI-907; PD 109, 763-2, is a new non-sulfhydryl-containing, angiotensin-converting enzyme (ACE) inhibitor. The present investigation describes its ACE inhibitory properties and compares them to those of MK 421. The diacid of SCH 31846 inhibited rabbit pulmonary ACE with an IC50 of 2.2 nM (MK 421 diacid 2.5 nM). The drug behaved as a competitive and specific inhibitor in vitro. SCH 31846 and its diacid effectively inhibited pressor actions of intravenous injection of angiotensin I (AI) in anesthetized rats. ID50 values were 27 and 11 micrograms/kg for SCH 31846 and SCH 31846 diacid, respectively (MK 421 and MK 421 diacid 57 and 15 micrograms/kg, respectively). Oral administration of SCH 31846 (0.03-1 mg/kg) inhibited pressor actions of AI in conscious rats with a duration of over 16 h at 0.3 and 1 mg/kg. SCH 31846 was 2.2 times as potent as MK 421 in this regard. The diacid of SCH 31846 was considerably less potent than the ester, implying poor oral absorption of the former. Effective ACE inhibition, as judged by attenuation of pressor actions of AI, was noted in dogs after both intravenous and oral administrations of SCH 31846. Onset of action was more rapid than that of MK 421. Intravenous administration of SCH 31846 inhibited the renal vascular actions of intrarenal injection of AI, indicating effective blockade of the renal enzyme. Intracerebroventricular administration of SCH 31846 diacid blocked pressor responses to intracerebroventricular AI, whereas oral administration of SCH 31846 (10 mg/kg) did not, implying that SCH 31846 inhibits brain ACE but does not gain access to the cerebral enzyme when administered orally. These data indicate that SCH 31846 is a potent and specific non-sulfhydryl ACE inhibitor. As such, it should be useful in the treatment of hypertension and heart failure.

The present study examined the actions of spiraprilic acid, a new non-sulfhydryl angiotensin converting enzyme (ACE) inhibitor upon aortic compliance (AC) in anesthetized dogs. Enalaprilic acid was examined for comparative purposes. AC was determined via sonomicrometric determination of the ratio of aortic systolic-diastolic diameter (mm) and arterial pulse pressure (mmHg). One AC unit (ACU) equals 10(-3) mm/mmHg. In non-thiazide pretreated animals, spiraprilic acid (1 mg/kg i.v.), caused a sustained hypotensive response of 21 +/- 3 mmHg (P less than .05). At the same time, aortic systolic and diastolic dimensions were reduced from basal values of 8.17 +/- 0.45 and 7.95 +/- 0.40 mm by 0.19 +/- 0.07 (P less than .05) and 0.29 +/- 0.10 mm (P less than .05), respectively. The aortic systolic-diastolic dimension rose significantly by 0.10 +/- 0.01 mm. Since pulse pressure was unchanged, AC rose from a basal value of 4.6 +/- 0.8 ACU by 1.7 +/- .3 ACU (P less than .05). Similar effects were observed with enalaprilic acid. In dogs pretreated orally with 5 mg/kg hydrochlorothiazide (HCTZ) twice daily for 3 days, spiraprilic and enalaprilic acids caused slightly greater falls in blood pressure (34 +/- 7 and 30 +/- 4 mmHg, respectively) than in nonpretreated dogs. However, the onset of the hypotension effect was more rapid for both ACE inhibitors in HCTZ-pretreated dogs. Effects of spiraprilic and enalaprilic acid upon aortic dimensions were similar to those observed in non-HCTZ pretreated animals. The data illustrate that the ACE inhibitors spiraprilic and enalaprilic acids not only lower blood pressure but also enhance large artery compliance.

Acetyl glyceryl ether phosphoryl choline (AGEPC) is a potent vasodilator, platelet activator and inflammatory agent. The cardiac and peripheral vascular effects of AGEPC were assessed in anesthetized dogs in order to gain additional insight into the mechanism of action of this lipid. Injection of AGEPC (0.1-3.2 micrograms) directly into the femoral vasculature produced a dose-related vasodilation in the innervated and sympathetically denervated hindlimb. Vasodilator responses in the denervated limb were at least as great as those in the innervated limb, which indicates that the response is not due to inhibition of sympathetic vasoconstrictor tone. Vasodilator responses to AGEPC (1 microgram) were not significantly affected by theophylline (5 mg/kg), indomethacin (5 mg/kg) or BW755C (10 mg/kg), which implies that the effect is independent of purinergic P1 receptors, cyclooxygenase products and lipoxygenase products. Intracoronary injection of AGEPC (0.032-3.2 micrograms) reduced blood pressure, myocardial contractile force and coronary blood flow in a dose-related manner. Coronary vascular resistance was unchanged. In contrast, intracoronary injection of another activator of platelets, ADP (10 micrograms), increased blood flow. Responses of blood pressure, heart rate, contractile force and coronary flow to AGEPC were not affected by bilateral vagotomy or hexamethonium, which indicates that they are independent of reflexive mechanisms. Indomethacin attenuated the hypotension and coronary flow reductions to AGEPC. BW755C reduced the hypotensive response. Mechanical reduction of coronary flow by 30 to 40% did not affect blood pressure, heart rate or contractile force, which suggests that AGEPC-induced changes are not secondary to flow reduction. The data suggest that AGEPC produces direct myocardial depression and distinct effects on the coronary and femoral vasculature. The peripheral vascular effects are independent of the autonomic nervous system, purinergic mechanisms and arachidonic acid metabolites, whereas some coronary effects may be mediated through metabolites of arachidonic acid.

SCH 33861 (7- N- 1(S)-(Carboxy)-3-phenylpropyl -(S)-alanyl 1,4-dithia-7-azaspiro 4.4 nonane-8(S)-carboxylic acid) is a novel, non-sulfhydryl angiotensin converting enzyme (ACE) inhibitor with marked topical ocular hypotensive activity. The present study evaluated the degree of systemic ACE inhibition resulting from topical administration of 0.01 and 0.1% concentrations (10 and 100-fold greater than needed to lower IOP) of SCH 33861 in conscious rabbits. For reference purposes, captopril, a prototype ACE inhibitor, was examined at concentrations 5 and 20-fold greater than needed to lower IOP. Neither 0.01 nor 0.1% topical SCH 33861 led to inhibition of pressor responses to 0.3 micrograms/kg iv challenges with angiotensin I (AI) over a 4 hr period. Captopril, in contrast, caused significant attenuation of AI pressor responses. The magnitude and duration of systemic ACE inhibition following captopril administration was concentration related. Intravenous administration of the same dose administered topically did not cause any systemic ACE inhibition with 0.01% SCH 33861. Following iv 0.1% SCH 33861, 0.5 or 2.0% captopril, AI responses were inhibited 60-70% indicating the ability to inhibit ACE if any systemic absorption took place. Topical administration of 0.01% SCH 33861 twice daily for five days also did not produce systemic ACE inhibition. These findings indicate that topical amounts of SCH 33861 greatly in excess of those needed to effect reductions in IOP have an exceptionally low potential for producing systemic effects.

We tested the ability of verapamil (V), diltiazem (DTZ) and nifedipine (NIF) to alter aortic compliance upon i.v. administration in anesthetized dogs. Sonomicrometry was used to measure aortic systolic (SD) and diastolic (DD) diameters. Aortic distention (AD) was calculated from SD-DD. Aortic compliance was computed from the ratio of AD to arterial pulse pressure. One aortic compliance unit (ACU) is defined as 10(-3) mm/mmHg. V (0.1-3.0 mg/kg) reduced blood pressure, SD and DD dose-dependently. DD was more affected than SD and AD rose significantly. Since pulse pressure was not significantly altered, V induced a dose-related increase in aortic compliance. The 3.0 mg/kg dose increased aortic compliance by 10.3 +/- 1.5 ACU from a basal value of 4.7 +/- 0.5 ACU. DTZ (0.1-3.0 mg/kg) produced effects on blood pressure, aortic dimensions and aortic compliance similar to those seen with V. Infusion of NIF (3.2-32 micrograms/kg/min) exhibited a similar profile, i.e., reduced blood pressure, SD, DD and increased AD and aortic compliance. NIF, however was limited in its ability to increase aortic compliance, i.e., increases of 3.2 +/- 1.0 or 3.8 +/- 0.6 from basal values of 4.9 +/- 1.0 ACU were obtained with 10 and 32 micrograms/kg/min NIF, respectively. Although these 3 prototype calcium entry blockers share a common profile of action, V and DTZ appear to have a greater efficacy on aortic compliance than NIF.

The present study examined the actions of dilevalol, an antihypertensive beta-adrenoceptor blocker with arterial vasodilator actions, on aortic compliance (AC) in anesthetized dogs. AC was measured by sonomicrometric determination of the ratio of aortic systolic-diastolic diameters (mm) and arterial pulse pressure (mm Hg). One AC unit (ACU) equals 10(-3) mm/mm Hg. Dilevalol (0.032, 0.1, and 3.2 mg/kg intravenously, i.v.) significantly (p less than .05) increased AC by 1.4 +/- 0.3, 3.7 +/- 1.4, and 4.5 +/- 1.2 ACU from basal values of 4.7 +/- 0.4-5.6 +/- 0.4 ACU while reducing blood pressure by 20 +/- 2, 31 +/- 9, and 41 +/- 10 mm Hg, respectively (p less than 0.05). Increases in AC were not the passive result of altered blood pressure. Proximal mechanical aortic occlusion dropped systolic blood pressure as much as 70 mm Hg without altering AC. Hydralazine also (0.3 and 1.0 mg/kg i.v.) lowered blood pressure significantly (p less than 0.05) by 14 +/- 3 and 40 +/- 4 mm Hg but increased AC only at 1.0 mg/kg (+ 1.6 +/- 0.4 ACU, p less than 0.05). Phenylephrine (1-30 micrograms/kg i.v.) significantly raised blood pressure 25 +/- 3-95 +/- 8 mm Hg but decreased AC significantly by 1.2 +/- 0.3-2.4 +/- 0.3 ACU. Isoproterenol (ISO) (0.01-1.0 micrograms/kg) produced effects on AC similar to those of dilevalol. Propranolol pretreatment attenuated dilevalol and ISO-induced increases in AC. Propranolol (0.32 and 1.0 mg/kg) did not significantly change AC.(ABSTRACT TRUNCATED AT 250 WORDS)

Dilevalol (SCH 19927) is a potent, long-acting, nonselective beta-blocker with marked vasodilator actions. Unlike classical beta-blockers, dilevalol promptly lowers blood pressure and vascular resistance in animal models of hypertension. The present studies address the peripheral vascular effects of dilevalol and explore the role of beta-receptor agonism in the acute vasodilator and antihypertensive effects of the compound. In the denervated dog hindlimb preparation, dilevalol (0.1, 0.3, 1.0 and 3.0 micrograms, i.a.) significantly increased femoral blood flow by 12 +/- 6, 27 +/- 6, 84 +/- 31 and 132 +/- 41 ml/min, respectively. In contrast, celiprolol, a beta-blocker with purported vasodilator activity, caused a significant increase in flow of 31 +/- 9 ml/min at a dose of 30 micrograms i.a. Systematic pretreatment with the selective beta 2-antagonist ICI 118,551 virtually abolished dilevalol's vasodilator effect in the dog hindlimb. In conscious spontaneously hypertensive rats, 3 mg/kg i.v. dilevalol reduced blood pressure by 58 +/- 8 mmHg (P less than 0.05) and vascular resistance by 171 +/- 27 dyne.sec.cm-5/100 g (P less than 0.05) but did not change cardiac output significantly. Pretreatment of spontaneously hypertensive rats with ICI 118,551 significantly reduced both dilevalol's antihypertensive and resistance-lowering effects. Oral doses of 10 and 25 mg/kg dilevalol lowered blood pressure by 19 +/- 3 (P less than 0.05) and 37 +/- 5 mmHg (P less than 0.05) in spontaneously hypertensive rats with chronically implanted Doppler flow probes. The lower dilevalol dose reduced mesenteric vascular resistance 38 +/- 6% (P less than 0.05) while the higher dose significantly lowered vascular resistance in the hindlimb, mesenteric and renal vascular beds of spontaneously hypertensive rats by 18 +/- 8, 33 +/- 2 and 43 +/- 4%, respectively. Propranolol lowered neither blood pressure nor regional vascular resistances at the above doses in spontaneously hypertensive rats. Thus, dilevalol promotes a generalized fall in vascular resistance. Furthermore, the present studies illustrate that beta 2-receptor stimulation plays an obligatory role in both the vasodilatory and antihypertensive actions of dilevalol.

The present study examined the actions of dilevalol, an antihypertensive beta-adrenoceptor blocker with arterial vasodilator actions, upon aortic compliance (AC) in anesthetized dogs. AC was determined via sonomicrometric determination of the ratio of aortic systolic-diastolic diameters (mm) and arterial pulse pressure (mm Hg). One AC unit (ACU) equals 10(-3) mm/mm Hg. Dilevalol (0.032, 0.1, and 3.2 mg/kg i.v.) significantly (p less than 0.05) increased AC by 1.4 +/- 0.3, 3.7 +/- 1.4, and 4.5 +/- 1.2 ACU, respectively, from basal values of 4.7 +/- 0.4-5.6 +/- 0.4 ACU, while reducing blood pressure by 20 +/- 2, 31 +/- 9, and 41 +/- 10 mm Hg, respectively (p less than 0.05). Increases in AC were not the passive result of altered blood pressure. Proximal mechanical aortic occlusion dropped systolic blood pressure as much as 70 mm Hg without altering AC. Propranolol (0.32 and 1.0 mg/kg) did not significantly change AC, but propranolol pretreatment attentuated dilevalol-induced increases in AC. Pindolol (0.1-1.0 mg/kg i.v.) lowered blood pressure 17 +/- 3 (p less than 0.05) to 34 +/- 7 mm Hg (p less than 0.05), while significantly increasing AC by 1.2 +/- .2 to 2.7 +/- .7 ACU. The data show that dilevalol, unlike propranolol, increases AC substantially at antihypertensive doses. The inhibition of dilevalol-induced AC increases by propranolol illustrates a beta-adrenoceptor agonist activity in large arteries. Since large artery compliance is impaired in hypertension, dilevalol may afford a vasular protective action for known risk factors for evolving systemic arterial disease.