Stephen Krop

Acute cardiomyopathy induced by the vasodilating antihypertensive agent minoxidil

Abstract Minoxidil, a vasodilating antihypertensive drug, was given orally in doses of 0.5, 1.0, or 3.0 mg/kg to adult Beagle dogs on 2 consecutive days. Within 2 hr of administration, each of these doses produced hypotension and a marked tachycardia which persisted for as long as 24 hr after the second dose of minoxidil. Necropsies performed 24 hr after the second dose revealed focal, superficial areas of epicardial or endocardial hemorrhage in dogs given each of the three dose levels. Hemorrhage was associated with a mild inflammatory reaction and was not limited to the right atrium. Focal arteritis, characterized by extravasation of blood and by focal accumulation of erythrocytes and fibrin-like material in the walls of small coronary arteries, occurred in three hearts from the 3-mg/kg dose group. Myocardial necrosis was noted in one of eight dogs given the minimal pharmacologic dose of 0.5 mg/kg, and in five of eight dogs in each of the groups given 1 or 3 mg/kg. Necrosis was most frequent in the left ventricular papillary muscles, particularly the posterior one. An ischemic origin of the necrosis is suggested by the localization of the lesions and by the pharmacologic effects of minoxidil.

Ethanol enhancement of blood-brain barrier permeability to catecholamines in chicks

Abstract The effect of ethanol (EtOH) on permeability of the blood-brain barrier (BBB) to parenteral catecholamines was investigated in neonate chicks. Animals simulataneously administered EtOH, 2 g/kg, and norepinephrine (NE), 5 mg/kg, or epinephrine (E), 5 mg/kg, entered a roosting state which was more pronounced than that observed after either amine alone. Roosting chicks were killed 2 min after NE + EtOH and 10 min after E + EtOH for whole brain amine analysis. NE + EtOH treatment resulted in a 220% increase in whole brain NE over controls receiving this amine alone, whereas E + EtOH produced a 29% increase in brain E. EtOH alone did not alter endogenous levels of either amine in brain. Results indicate that EtOH, a solvent whose solubility characteristics allow it to penetrate easily both aqueous and lipoid membrane components, facilitates entry of E and NE into the brain of the neonate chick across an imperfect BBB present at hatching.

Effects of various drugs on 3,4-dihydroxyphenylalanine (dl-DOPA)-induced excitation (agressive behavior) in mice☆

Abstract dl -DOPA given iv to mice promptly induces an aggressive central excitation, i.e., a biting response, furnishing the basis for a method for “screening” for psychoactive action in drugs. Twenty-two compounds were effective in suppressing the biting response. The 10 most active drugs, according to the ED50 values (mg/kg, ip), are: trifluoperazine, 0.15; reserpine, 0.18; haloperidol, 0.9; chlorpromazine, 2.4; diazepam, 2.5; morphine, 5.2; bretylium, 5.6; oxazepam, 8.8; imipramine, 11.5; and chlordiazepoxide, 13. Iproniazid and tranylcypromine potentiated the biting response induced by dl -DOPA. Seven compounds have high therapeutic indices ( LD 50 ED 50 ) by this method: trifluoperazine, 1233; reserpine, 389; diazepam, 150; oxazepam, 104.5; morphine, 53.9; chlorpromazine, 49; and haloperidol, 47.

Increase of blood-brain barrier permeability to catecholamines by dimethyl sulphoxide in the neonate chick

Parenteral adrenaline or noradrenaline, because they cross a permeable blood-brain barrier in young chicks, produce sustained roosting or sleeping behaviour (Key & Marley, 1962; Spooner, Mandell & others, 1968; Hanig & Seifter, 1968). This phenomenon disappears within 6-8 weeks as the various components of the central nervous system mature (Waelsch, 1955 ; Lajtha, 1957). Several years ago, Brink & Stein (1967) showed that dimethyl sulphoxide (DMSO) facilitated the entry of [14C]pemoline into the brain of rats. Recently, De La Torre (1970) has shown that DMSO increases the relative penetration of L-dopa and 5-HTP across the blood-brain barrier of the rat. DMSO is an industrial solvent with skin-penetrating effects, and the ability to carry into the body toxic substances that are normally excluded (Stoughton & Fritsch 1964; Kligman, 1965; Narula, 1967). Since DMSO has both aqueous and lipid solubility characteristics that allow it to penetrate the central nervous system easily, it was chosen as a prototype compound for study of blood-brain barrier biogenic amine interaction in the neonate chick. We observed that DMSO intensified roosting induced by adrenaline and noradrenaline in the neonate, and therefore sought to determine whether this was associated with increased penetration of catecholamines into chick brain (Hanig, Morrison, & Krop, 1970). One-day-old chicks housed in a temperature-controlled brooder were given free access to food and water and used within one week. Adrenaline or noradrenaline was dissolved in 0.9% NaCl or 50% DMSO--O.9% NaCl and administered (5 mg/kg, i.v.) into the jugular vein. This corresponded to a dose of 2.75 g/kg of DMSO which is well below the single dose toxicity for various species described by Smith, Hadidian & Mason (1967). Chicks were decapitated 10 min after adrenaline administration, but 2 min after noradrenaline because of its rapid turnover in the brain. Both amines in whole brain were estimated by an automated fluorimetric procedure (Hanig, Morrison & Krop, 1969). The grossly observable behaviour of DMSO alone in chicks was minimal except for a transitory arousal that lasted for several seconds after injection, whereas those receiving adrenaline or noradrenaline with DMSO exhibited a roosting response that was more intensified than that observed with the same dose of either amine alone. Preliminary chemical studies showed no difference in endogenous amine concentra tions between animals treated with saline or those treated with DMSO alone (Hanig & others, 1970). Administration of adrenaline + DMSO gave a highly significant increase of 34.8% in concentrations of this amine in brain over controls receiving the same dose of adrenaline alone. Similarly, noradrenaline + DMSO treatment gave

Doxorubicin-induced hypotension in the beagle dog

Rapid intravenous administration of doxorubicin (0.18–3.0 mg/kg) lowered systemic arterial pressure in anesthesized beagle dogs. The threshold hypotensive dose was between 0.375 and 0.75 mg/kg; doses of 1.5–3.0 mg/kg produced up to 75% depression of arterial pressure for periods of 15 to >30 min. Respiratory difficulty was also present at these doses. When doxorubicin (1.5 mg/kg) was given repeatedly, the magnitude of the hypotensive response decreased with each succeeding dose. Pretreatment with either atropine (1.0 mg/kg) ordl-propranolol (0.5 mg/kg) did not alter the fall in arterial pressure due to doxorubicin administration. In contrast, the response was almost completely eliminated when compound 48/80 (1 mg/kg) was given 1 h prior to doxorubicin (1.5 mg/kg). Also, the intensity and duration of the hypotensive response was decreased by pretreatment with the H1 histamine blocker tripelennamine (6 mg/kg), while the response was almost completely eliminated in animals pretreated with a combination of tripelennamine (6 mg/kg) and the H2 histamine blocker cimetidine (15 mg/kg). Significant increases in plasma histamine were detected immediately after the injection of doxorubicin (1.5 mg/kg).Thus, rapid release of histamine following administration of low doses of doxorubicin decreases systemic arterial pressure; this response can be attenuated by agents that alter the action of histamine.

Convulsions in weanling rabbits after a single topical application of 1% lindane

Abstract There have been sporadic reports of adverse effects of lindane (γ-hexachlorocyclohexane) in children treated for scabies. These effects usually consisted of tremors, convulsions, anorexia, and possible stunting of growth. Weanling rabbits (6 weeks old; 1.0 kg) given a single topical application of 1% lindane at a dose reportedly used in infants (60 mg/kg) exhibited severe anorexia and convulsions; death occurred in some cases. The effects were more pronounced in weanlings in which the skin was inflamed or not completely intact. In contrast, young adult rabbits (2–3 kg) given the same dose showed only some anorexia and possibly mild excitement. Concentrations of lindane in whole blood of weanlings at the time of convulsion (approximately 24 hr after dosing) ranged from 0.7 to 2.5 μg/ml. These findings suggest a rather pronounced sensitivity of weanlings to lindane in comparison to adults.

Observations on hexachlorophene-induced paralysis in the cat and its antagonism by hypertonic urea.

Summary Cats given HCP (20 mg/kg) orally each day developed hindlimb paralysis and greatly elevated CSFP (174 mm saline; 19 mm in controls) in 3 to 5 days. “Status spongiosis” was seen in white matter only in sections of brain and cord. There was no dilation of cerebral ventricles, or damage to their ependymal linings or to the arachnoid villi. The neurological picture excluded any but a terminal effect upon cranial nerve function. There appeared to be no damage to neurons, and recovery of survivors was complete within 6 weeks after cessation of HCP administration. Elevated CSFP in paralyzed anesthetized cats was quickly lowered by an average of 256 mm by slow iv administration of 30% urea (2 g/kg in 10% invert sugar). Unanesthetized cats similarly paralyzed were able to stand and walk for up to 4 hr after this treatment. Neither acetazolamide nor prednisolone alone had any effect, nor did coadministration with urea enhance the effect of urea. The HCP lesion does not appear to be inflammatory in origin, nor does it seem to involve ventricular obstruction or overproduction of cerebrospinal fluid. The reappearance of paralysis about 4 hr after osmotic diuresis, which corresponds with the elimination of urea, suggests that prolonged iv infusion with urea or a similar osmotically active substance may have significant clinical value in the management of HCP poisoning. We wish to thank Dr. Renate D. Kimbrough of the Center for Disease Control for her generous assistance and expert opinion on a portion of the preliminary neuropathology studies; Dr. Joseph Fenstermacher and his staff of the National Institutes of Health for their excellent advice on the performance of cerebrospinal fluid measurements; Dr. Andrew Ulsamer of the Consumer Product Safety Commission for expert guidance and assistance with the hexachlorophene analytical procedure; and Dr. Rogelio A. Zaldivar of the Food and Drug Administration for the excellent veterinary care of our animal colony.

Protection with butylated hydroxytoluene and other compounds against intoxication and mortality caused by hexachlorophene

The antioxidants butylated hydroxytoluene (BHT) and ethoxyquin protected rats against intoxication and mortality normally produced by hexachlorophene (HCP, 100 mg/kg). BHT also prevented the elevation of cerebrospinal fluid pressure, a central nervous system effect of HCP poisoning. In addition, both phenobarbital and SKF-525A protected against HCP poisoning, with the barbiturate also offering significant protection against triethyltin. L-Ascorbic acid, vitamin E, N,N-diphenyl-p-phenylenediamine and reduced and oxidized glutathione over a range of doses were ineffective in preventing HCP lethality. The protective effect of phenobarbital against HCP and triethyltin intoxication further supports existing evidence of a common or similar mechanism of toxic action for these two structurally dissimilar compounds.

Acute toxicity of paralytic shellfish poison in rats of different ages.

Summary Age of the animal modifies the toxicity of paralytic shellfish poison administered orally to rats. This influence is of less importance when the toxin is administered intraperitoneally. Weanlings and young adults receiving lethal doses of the toxin exhibit an anoxic type of convulsion before death, whereas newborns die without exhibiting a convulsive seizure. However, newborn rats exhibit seizures when treated with strychnine or pentylenetetrazole. Although paralytic shellfish poison given orally is more toxic to newborn and weanling animals, these rats are able to survive a significantly longer period of time than the young adults. When changes in the electrocardiogram are followed in the three groups of rats receiving a lethal dose of toxin orally, bradycardia is found to occur more rapidly and to a greater degree in the newborns than in the older animals. Auricular conduction defects are also more prominent in newborns. Ventricular conduction time is not significantly altered in any age group. Partial to complete A-V dissociation occurs prior to death in all groups.

A semi-automated method for fluorimetric determination of epinephrine and norepinephrine, without mutual interference, in single brain samples

Abstract A method is described for the separation and automated fluorimetric determination of epinephrine and norepinephrine in brain tissue extracts without mutual interference. The catecholamines are isolated and purified by extraction from activated alumina. Oxidation and rearrangement to their fluorescent lutines is carried out on two separate AutoAnalyzer manifolds and fluorescence is read in an Aminco-Bowman spectrophotofluorimeter. The interference by one amine with the determination of the other is less than 1% for determination of epinephrine in the presence of an equimolar concentration of norepinephrine, and, conversely, less than 4% for determination of norepinephrine. This eliminates the need for solution of simultaneous equations, the results of which are often misleading when the ratio of one amine to the other in brain exceeds 10:1. This method can be useful for rapid screening of psychoactive compounds affecting central and peripheral adrenergic stores.