To elucidate the functional connections between dopaminergic, GABAergic and opioid peptidergic systems in rats, electrophysiological, behavioral, neurochemical and histological investigations have been undertaken, focusing on the changes in drug sensitivity in the central nervous system (CNS). Changes in sensitivity in the CNS can be induced by denervation, chronic administration of antagonists or agonists, and by the inhibition of the axoplasmic transport system. It is conceivable that the changes in sensitivity of the CNS to transmitters may be related to the etiology of mental illnesses such as schizophrenia and mania and may be related to the symptoms of Parkinson's disease. Investigation of changes in sensitivity of the CNS to transmitters or drugs may provide the key for elucidating the biological nature of mental illness.
Effects of morphine microinjected into the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei, which contain neurons producing and releasing antidiuretic hormone (vasopressin), on the outflow and the osmotic pressure of urine and other visceral functions were investigated in a rat which was loaded with water and anesthetized with ethanol. The opioid drug, having predominantly mu-agonist activity, when microinjected into the SON or PVN induced potent antidiuretic effects in dose-dependent and time-dependent manners with no significant effects on the other visceral functions. The approx. ED50 values for morphine were 19 and 9 nmol when it was microinjected into the SON and PVN, respectively. The antidiuretic effects showed slow onset and long duration, with a minimal outflow at approx. 50 min after microinjection and a return to approx. 50% of the initial control value by 1.5 hr. The morphine-induced effects were inhibited by pretreatment with naloxone or atropine, but not inhibited by pretreatment with alpha or beta-adrenoceptor antagonists, suggesting that the antidiuretic effects were mediated through an opioid receptor having low sensitivity to naloxone and also possibly mediated through a muscarinic receptor which was stimulated probably by the ACh released by morphine.
Young adult rats exposed to a 1 hr feeding schedule in activity-wheel cages daily, show immunological incompetence and stomach ulcer. This stress procedure is called “activity-stress (AS)”. The present study examined the effects of neurotropin (NSP), which is an extract from rabbit skin tissues inflamed with vaccinia virus, on the immunosuppression and stomach ulcer induced by AS. The i.p. treated NSP showed a significant immunopotentiation effect (50 and 100 mg/kg), but did not significantly prevent the ulceration, although i.p. treated NSP decreased the incidence of ulcer. The p.o. treated NSP revealed both immunopotentiation (50 and 100 mg/kg) and antiulcerogenic effects (100 mg/kg). However, the i.p. treatment of NSP seems to prevent atrophy of the thymus and spleen, but did not improve hypertrophy of the adrenals induced by AS. The p.o. treated NSP improved atrophy of the spleen and hypertrophy of the adrenals, but did not improve atrophy of the thymus. Since immunodeficiency and ulcer-production by AS are considered to be phenomena appearing in the exhaustion stage of the organism, the present study suggests that NSP can heal immunological incompetence and stomach-ulcer induced by stress. In addition, the present study discussed the different pharmacological activities of NSP based on differences between administration routes.
Neonatal castration completely suppressed the expression of P-450 male and expressed P-450-female; and testosterone treatment in a neonatal period partially reversed the effect of castration, i.e., neonatal imprinting (Kamataki et al., 1984; Waxman et al., 1985). In the present communication, we investigate the reversibility and persistency of neonatal imprinting on the expression of P-450-male and P-450-female. To our surprise, testostrone treatment at adulthood (8 weeks old) caused full expression of P-450-male and restored the activities of 2α and 16α-testosterone hydroxylases in neonatally castrated rats. The levels of ethyl morphine N-demethylation, propoxycoumarin 0-depropylation and benzo(a)pyrene hydroxylation were increased to the levels of adult male rats by adult testosterone treatment. Moreover, treatment with testosterone of neonatally castrated rats at the age of 19 weeks did not cause a complete recovery of P-450-male content and drug-metabolizing activities. Testosterone administration into neonatal female rats did not significantly alter the contents of sex-dependent cytochrome P-450 and drug and steroid metabolizing activities in adulthood. Additional testosterone treatment in adulthood only slightly affected these parameters. All these results indicate that neonatal androgen imprinting on sex-dependent cytochrome P-450 and drug and steroid metabolizing activities in rat liver microsomes is not a permanent programming process and is modified by the presence and absence of sex steroid hormones.
Fischer 344 (F344), Lewis (LEW), spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats were chronically fed food containing pentobarbital on an escalating drug dosage schedule over a period of 47 days. During treatment, the growth curve in LEW, SHR and WKY rats was suppressed as compared with the respective controls. Motor incoordination was evaluated by a rotarod performance test. The ranking of the motor incoordination was as follows: WKY>>j LEW>SHR>F344. After substitution of normal food for the pentobarbital-admixed food, various signs of pentobarbital withdrawal occurred. The withdrawal signs from pentobarbital in F344, LEW and SHR rats were mild as compared with those in WKY rats. The order of the severity of withdrawal signs in four inbred strains was parallel to that for motor incoordination. These results suggest that the differences between strains in withdrawal can be attributed to differences in the degree of chronic CNS depression produced by pentobarbital.
The effects of three calmodulin antagonists on rat parotid amylase release were investigated in vitro using a dispersed acinar cell preparation. The potent calmodulin antagonists, trifluoperazine (TFP) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), inhibited both 1 μM isoproterenol (ISO)- and 1 mM dibutyryl cyclic AMP (DBcAMP)-stimulated amylase release in a dosedependent manner at concentrations of 25-100 μM. The IC50 values for the ISO-stimulated amylase release were 22 μM with TFP and 42 μM with W-7, and the values for the DBcAMP-stimulated release were 25 μM and 48 μM, respectively. The weak calmodulin antagonist, N-(6-aminohexyl)-1-naphthalene-sulfonamide (W-5), caused only slight inhibition at a concentration of 100 μM. These calmodulin antagonists only had a very small effect on the spontaneous release of lactate dehydrogenase. The results suggest that the calcium-calmodulin system may play a role in the exocytotic process of amylase release from the rat parotid gland.
Pharmacological properties of SM-3997 (3aα, 4β, 7β, 7aα-hexahydro-2(4-(4-(2-pyrimidinyl)-1-piperazinyl)-butyl)-4, 7-methano-1H-isoindole-1, 3(2H)-dione dihydrogen citrate) have been examined in rats and mice. SM-3997 showed a dose-related anticonflict activity in rats in a water lick conflict paradigm, and it had no effect on water consumption in a spontaneous water drinking test. The potency of SM-3997 appeared to be equal to that of buspirone and about one-half that of diazepam. No tolerance to the anticonflict activity of SM-3997 was observed following 5 and 10 consecutive days of treatment. Unlike diazepam, SM-3997 had no anticonvulsant effect and had very weak muscle relaxant and hypnotic effects. On the other hand, SM-3997 and buspirone exhibited dopamine antagonistic action, although the potency of SM-3997 was less than one fourth that of buspirone. These results show that SM-3997 is a new anxioselective anxiolytic agent which is weaker than buspirone in the dopaminergic neuron system.
The abilities of tricyclic ergot alkaloids, chanoclavine-I and its analogues, and bromocriptine to stimulate dopamine receptors in the brain were investigated. Receptor binding of 3H-spiperone has shown that bromocriptine exhibits clear affinity for this compound. The order of displacement potencies was bromocriptine >> ergometrine, KSU-1 415 > chanoclavine-I, KSU-1118, KSU-1791. In the striatum of mice treated with an amino acid decarboxylase inhibitor, γ-butyrolactone-induced DOPA accumulation was markedly inhibited by bromocriptine and KSU-1415, but not inhibited by chanoclavine-I. In mice with unilateral striatal 6-hydroxydopamine lesions, bromocriptine and KSU-1415 produced a long-lasting contralateral rotation that was suppressed by prior treatment with (±)-sulpiride. These results suggest that a tricyclic ergot alkaloid of the chanoclavine type stimulates D-2 receptors in the brain.
The effects of a newly synthesized compound, 2-[(5-chloro-2-methoxyphenyl)azo]-1H-imidazole (M6434) on α-adrenergic receptors were investigated by using the atria of normal and hypothyroid rats, rat vasa deferentia and canine arteries. M6434 showed a positive inotropic effect on rat left atria, which was suppressed by phentolamine but not by propranolol and reserpine. M6434 also showed a positive chronotropic effect on rat right atria. These positive inotropic and chronotropic effects of M6434 were enhanced in propylthiouracil-induced hypothyroid rats. M6434 caused contraction of rat vas deferens and increased its spontaneous movement. These effects on vas deferens were suppressed by phentolamine. M6434 induced contraction of canine arteries. The pD2 values for vasoconstrictive effects of M6434 on the aorta, pulmonary artery, renal artery and femoral artery were about equal to those of phenylephrine, and the intrinsic activity of M6434 was somewhat lower than that of phenylephrine. These results suggest that M6434 is an adrenergic α-agonist which is about as potent as phenylephrine and that M6434 has neither a β-stimulating activity nor a catecholamine-releasing one.
Phagocytic activity as a function of the reticuloendothelial system (RES) has been studied in ethionine induced liver injury by using the carbon clearance test. Liver damage in male and female mice was induced by DL- and L-ethionine injections (1000 mg/kg/day, i.p.). In both female and male mice, a single dose or three injections of DL- or L-ethionine caused increases in liver/body weight ratio, A/G ratio, GOT and GPT levels, and BSP retention. There was the decrease of the total protein levels in the serum. The degree of liver injury was more severe after three injections of DL- and L-ethionine than after a single injection of them. After a single injection of ethionine, the L-isomer induced a slightly greater response than the racemic mixture, except for BSP retention. On the other hand, phagocytic activities by the carbon clearance test were increased after a single injection or three injections of DL- and L-ethionine. That is, the K value was increased in all ethionine treated mice except for females with three injections of DL-ethionine. The α value was increased after three injections in DL- and L-ethionine treated males and DL-ethionine treated females. In addition, the increase in carbon uptake by Kupffer cells can be seen by light microscopy after a single injection or three injections of DL- or L-ethionine. These findings indicate that ethionine injections induce the enhancement of RES phagocytosis, although the biochemical parameters indicating liver injury are changed severely. These results support the data indicating no correlation between the alteration of RES activity and the degree of liver injury.
In mice, combined addition of 1% cholesterol and 0.5% cholic acid to a diet induced cholesterol gallstones within 40 days as a result of the supersaturation of cholesterol in the bile, as has been reported. The major component of the gallstone was cholesterol, which was measured by HPLC. In this study, however, single addition of 1% cholic acid to a diet, which did not decrease cholesterol solubilizing capacity in bile, contributed to gallstone formation in mice within 50 days. The gallstones thus formed contained a large amount of palmitic acid. In the hepatic bile of this animal, palmitic acid was also detected; however, no solid material was observed by light and polarized-light microscopes. Free fatty acids such as palmitic acid seem to be dissolved in a complex micelle composed of bile acids and lecithin. This probably causes gallstone formation by reducing cholesterol solubilizing capacity in bile.
The in vivo effects of alcohol-metabolizing enzyme inhibitors and beta-lactam antibiotics upon the ethanol elimination rate were examined in rats. Intravenous administration of ethanol caused a dose-dependent increase in blood ethanol level, and the ethanol elimination could be well described by a two compartment model. Pretreatment of rats with enzyme inhibitors caused a marked decrease in the ethanol elimination rate associated with the depression of the enzyme activities. Fasting of the animals caused a decrease in the ethanol elimination rate per animal associated with a decrease in the liver weight. However, no alteration was evident when the rate was expressed as the rate per g of liver. When animals were pre-treated with a high dose of N-methyltetrazolethiol (NMTT) containing beta-lactam antibiotics or NMTT itself, which causes a disulfiram-like reaction, the ethanol elimination rate per animal was depressed concomitant with an increase in the blood acetaldehyde level. The ethanol elimination rate in these animals showed lower values even when expressed as the rate per g liver. On the other hand, administration of cephems without NMTT, which cause no disulfiram-like reaction, led to a slight decline in the elimination rate per animal, although no alteration was detected when the rate was expressed as the rate per g liver. The findings indicated that the ethanol elimination in vivo per animal is regulated by the total capacity of the alcohol-metabolizing enzyme activities in the whole liver.
The influence of chronic pilocarpine administration on the recovery of the parotid gland from an obstruction was investigated by studying the amylase release induced by secretagogues in rats. Treatment with pilocarpine (5 mg/kg, daily for 7 days) increased amylase release induced by isoproterenol (10-5 M) or forskolin (10-5 M) in the parotid tissue of rats after the removal of a 7-day-duct ligation. However, there was no significant difference in the amylase activity of the parotid tissue between pilocarpine-treated rats and control rats. These results suggest that the accelerated recovery of amylase release from parotid tissue in rats chronically treated with pilocarpine may be due to the increased response of amylase release, rather than the increased accumulation of secretory materials in the cells; and furthermore, cyclic AMP-mediated events may be involved in the increased response of amylase release.
Effects of scopolamine (0.5 mg/kg, s.c.) on ambulatory activity were investigated in 6 strains of mice (dd, ICR, BALB, C57BL, C3H and DBA). Scopolamine increased ambulatory activity, and the sensitivities were in the order of ICR>C3H>BALB>DBA>C57BL>dd. This was different from that produced by methamphetamine (2 mg/kg, s.c.) where the order was ICR>dd>DBA>C3H>C57BL>BALB. A tolerance to the ambulation-increasing effect of scopolamine was progressively produced in dd, ICR, C57BL and DBA strains, but not in BALB and C3H strains, when the drug was administered 5 times at intervals of 3-4 days. The repeated scopolamine treatment elicited a major enhancement of the sensitivity to the ambulation-increasing effect of methamphetamine (2 mg/kg, s.c.) in BALB and C3H strains and a minor enhancement in the C57BL strain, whereas dd, ICR and DBA strains did not exhibit a marked change in the sensitivity to methamphetamine even after the same treatment with scopolamine. These results suggest that the ambulation-increasing effect of scopolamine is different from that of methamphetamine and that the interaction between scopolamine and methamphetamine varies among different strains of mice.
Hypolipidemic effects of γ-oryzanol (OZ) and cycloartenol ferulic acid ester (CAF) on the hyperlipidemia induced by ingestion of a high cholesterol diet (HCD) in male Sprague-Dawley rats were investigated. The test drugs were given orally and intravenously, daily for 12 days with the HCD feeding. The oral administration with OZ and CAF at 100 mg/kg daily for 6 or 12 days did not apparently prevent the hyperlipidemia induced by HCD-feeding. The intravenous administrations with OZ and CAF at 10 mg/kg for 6 days significantly inhibited the increases in serum total cholesterol (TC), phospholipid (PL) and free cholesterol by HCD. OZ and CAF did not inhibit the decreases of TC in high density lipoprotein (HDL-TC) and HDL-PL by HCD. The increases of atherogenic index ([TC-HDL-TC]/[HDL-TC] and [PL-HDL-PL]/[HDL-PL]) with the HCD feeding were reduced by the intravenous administrations of OZ and CAF. Triglyceride, nonesterified fatty acid, lactate dehydrogenase and transaminase (GOT and GPT) markedly decreased below the control level by the intravenous administrations of OZ and CAF for 12 days. These results suggest that the intravenous administrations of OZ and CAF may have accelerated the excretion of lipids in the blood.
The effect of intracerebroventricular (i.c.v.) injection of synthetic rat atrial natriuretic polypeptide (α-rANP) on drinking behavior was studied in normotensive rats, α-rANP (0.2, 0.4 or 0.8 μg in 5 μl) caused a dose-dependent dipsogenic effect which was abated by i.c.v. pretreatment with saralasine (9 μg in 5 μl). These results suggest that α-rANP possesses dipsogenic effects in water repleted rats and that brain angiotensin is involved. In addition, our data indicate that, at least as far as the effect of cerebral ANP is concerned, there are some differences between α-rANP and human atrial natriuretic polypeptide.
Two neurokinin B (NKB) analogs, [Gly6]-NKB [3-10] and [Arg3, DAla6]-NKB [3-10], were tested for agonistic activity as well as for their ability to antagonize the myotropic actions of NKB, neurokinin A, substance P, physalaemin and eledoisin in isolated guinea-pig ileum, guinea-pig urinary bladder, rat duodenum, rat vas deferens and rat portal vein. [Gly6]-NKB [3-10] in the guinea-pig ileum and rat portal vein and [Arg3, D-Ala6]-NKB [3-10] in the guinea-pig ileum were found to be the first specific and competitive antagonists against NKB.