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Possible involvement of 5-hydroxytryptamine and cyclic-AMP in tolerance to tremorine analgesia in mice.

The phenomenon of tolerance to the analgesic action of tremorine in mice was studied by the hot-plate and tail-clip methods. Reduction in 5-HT levels in brain by parachlorophenylalamine pretreatment decreased the ED50 of tremorine analgesia in tremorine tolerant mice. 5-Hydroxyptophan, L-Dopa or alpha-methyl-para-tyrosine did not influence the analgesic response to tremorine in tremorine tolerant animals. However, theophylline was found to enhance the tolerance to tremorine analgesia. Brain 5-HT and cAMP are probably involved in tremorine tolerance, whereas neither noradrenaline nor dopamine is involved in the phenomenon.

5-Hydroxytryptophan

Genetical differences in sensitivity to tremorine and oxotremorine in mice.

Male mice from 14 strains were injected i.p. with tremorine (3.0 mg/kg) or oxotremorine (0.15 or 0.1 mg/kg). Large inter-strain differences in the degree and duration of the subsequent hypothermia were noted. 2 strains, BALB/c and Simpson, were particularly sensitive to the hypothermic effect of oxotremorine. The offspring from a cross between BALB/c and Simpson were less sensitive than the parental strains, suggesting genetic complementation. A set of 7 recombinant inbred (RI) lines derived from strains C57BL and BALB/c were tested with oxotremorine. 5 RI lines resembled strain C57BL in their response and 2 RI lines resembled strain BALB/c. It was concluded that strains C57BL and BALB/c differ at a gene which has a major effect on the response to oxotremorine.

Animals

Tremorine-oxotremorine-induced tremor, hypothermia and analgesia, and physostigmine toxicity, in mice after pretreatment with beta-adrenoceptor antagonists.

The beta-adrenoceptor blockers propranolol, PhQA33 and LB-46 exhibited appreciable activity against tremorine-(TMN) and oxotremorine-(OTMN) induced tremor, whereas pronethalol, (+)-H56/28, (-)-H56/28, Kö-592 and L(+)-INPEA possessed weak action. The two beta-blockers, namely D,L(+/-)-INPEA and D(-)-INPEA acted as weak tremorgens. None of the above compounds suppressed the induced peripheral cholinergic phenomena; or possessed any central anticholinergic activity, as they were unable to afford protection against physostigmine-induced death. Propranolol, PhQA33 and LB-46 antagonized TMN-induced hypothermia and analgesia, but were inactive against OTMN-induced changes. A correlation of the beta-blocking and anti-tremor activity of these agents is unlikely.

Adrenergic beta-Antagonists

Oxotremorine-tolerance: muscarinic blockade or homeostatic adaptation?

Tremorine pretreatment of mice induces tolerance to some effects of oxotremorine. In the state of tolerance even the highest doses of oxotremorine did not cause antinociception, this blockade being insurmountable. Oxotremorine decreased motility and amphetamine hypermotility, and both effects were diminished by tremorine pretreatment. Amphetamine hypermotility increased in the tolerance state. The increase of cerebral acetylcholine level due to oxotremorine was diminished by tremorine pretreatment. It is suggested that a special blockade of cerebral muscarinic receptors might play a role in the tolerance phenomenon, moreover it is possible that some excitation develops in the CNS. A homeostatic adaptation may be involved a role in this kind of tolerance.

Acetylcholine

Direct or indirect action of histamine on dopamine metabolism in the rat striatum?

Intraventricular administration of 500 microgram of 2-pyridylethylamine, an agonist of the histamine (Hi) H1-receptor, produced a 20% increase of striatal HVA in the rat while the Hi H2-receptor agonist 4-methylhistamine had no influence on HVA and DOPAC levels. L-Histidine (1.5 g/kg) or amodiaquine (60 mg/kg) given i.p. increased HVA and DOPAC levels to the same extent as did pyridylethylamine. Histidine combined with tremorine had an additive effect with respect to the increase of DA acidic metabolites while mepyramine slightly attenuated the tremorine-induced rise of HVA.

3,4-Dihydroxyphenylacetic Acid

[Inhibition of harmaline induced tremor by L-threo-3, 4-dihydroxyphenylserine, an L-norepinephrine precursor].

Effect of 3, 4-dihydroxyphenylserine (DOPS), a norepinephrine precurosr, on harmaline tremor was investigated in mice to elucidate the role of norepinephrine in the genesis of tremor. 1) Spontaneous motor activity was inhibited by L-threo-DOPS (200 mg/kg i.p.). 2) Tremor induced by harmaline (5 and 7 mg/kg i.p.) was enhanced by alpha-methyl-p-tyrosone (200 mg/kg i.p.). 3) The development and duration of tremor induced by harmaline (10 mg/kg i.p.) were inhibited significantly in a dose dependent manner by L-threo-DOPS (50, 70, 100, 150 and 200 mg/kg i.p.), but neither by D-threo-DOPS (200 mg/kg i.p.) nor DL-erythro-DOPS (200 mg/kg i.p.). 4) L-threo-DOPS (200 mg/kg i.-.) had no effect on the development of tremor induced by tremorine (5 and 10 mg/kg i.p.), while lacrimation and diarrhea caused by tremorine was markedly inhibited. 5) Administration of harmaline (10 mg/kg i.p.) produced an increase in brain 5-hydroxytryptamine content but not in that of norepinephrine. Administration of L-threo-DOPS (100 mg/kg i.p.) increased the norepinephrine content but not the 5-hydroxytryptamine content in the brain. Inhibition of harmaline tremor induced by L-threo-DOPS is attributed to the L-norepinephrine converted from L-threo-DOPS and the involvement of a noradrenergic mechanism in harmaline tremor has to be considered.

Alkaloids

Pharmacology of Quercus infectoria.

The galls of Quercus infectoria (Fagaceae), a commonly available plant in Iran, were studied pharmacologically. Two fractions were employed, a dried acetone-treated methanol extract dissolved in water (Fraction A) and a subfraction prepared by chloroform-methanol extraction (Fraction B). Fraction A was active as an analgesic in rats and significantly reduced blood sugar levels in rabbits. Fraction B had CNS depressant activity. Data obtained with a treadmill indicated a decreased activity ratio by Fraction B, suggesting a possible interference in motor coordination. It potentiated the barbiturate sleeping time significantly without changing the onset time or the loss of the righting reflex. In addition, Fraction B exhibited a moderate antitremorine activity by causing a delay in the onset and a decrease in the severity of tremorine-induced tremors. The local anesthetic action of Fraction B was evident due to the complete blockade of the isolated frog sciatic nerve conduction.

Analgesics

Parasympatholytic (anticholinergic) esters of the isomeric 2-tropanols. 1. Glycolates.

The 38 esters in Table I were prepared from the four isomeric 2-tropanols and a variety of racemic glycolic acids and their optical isomers. Anticholinergic activity in mice was measured in the peripheral nervous system (mydriasis) and in the central nervous system (anti-tremorine) and compared with that of atropine, scopolamine, and racemic 2-quinuclidinyl benzilate. The results (Table III) showed that several esters (such as 8, 12, 14, and 21) had significantly greater activity in both the peripheral and central nervous systems than did the reference compounds. Esters of (+)-2alpha-tropanol were more potent than those of either its epimer (-)-2beta-tropanol or its optical isomer(-)-2alpha-tropanol. Esters derived from (-)-glycolic acids were uniformly more potent than those from the (+)-glycolic acids. Esters of (+)-2alpha-notropanol and five of its N-substituted derivatives had markedly decreased activity. Peripheral/central activity ratios and time-activity profiles for five active compounds are discussed and compared with those of the reference compounds.

Animals

[Central activity, antihypertensive action and antiulcerogenic effects of neurotropin].

Central activity, antihypertensive action and antiulcerogenic actions of Neurotropin (NSP), an extract isolated from vaccinia virus-innoculated skin or tissues of rabbits were investigated herein. When actions of NSP were examined in isolated muscle preparations by the Magnus-method, peristalsis and ACh-induced contraction in the small intestine isolated from crayfish were not influenced, peristalsis and ACh-induced contraction in the small intestine from mice were slightly accelerated, but adrenaline-induced relaxation in the small intestine from mice was not affected. Histamine-induced contraction in the small intestine and tracheal muscles isolated from guinea pigs was antagonized slightly, or not at all by NSP in a high concentration. NSP had no direct action nor anti-ACh action on abdominal muscles from frogs. NSP had no influence on E1-mice-convulsions. Both spontaneous motor activities and exploratory movements in mice were depressed. Sleeping time induced by hexobarbital-Na was prolonged in mice. Tremorine-induced tremor in mice was inhibited by NSP, while perphenazine-induced catalepsy in rats was not. Normal blood pressure in Wistar rats was not influenced, but high blood pressure in SHR (spontaneously hypertensive rats) decreased close to normal levels after NSP. NSP had antiulcerogenic effects on Takagi's restraint-plus-water-immersing ulcers in rats and histamine-induced duodenal ulcers in guinea pigs, but no influence on Shay ulcers in Wistar rats. From the data obtained herein, it may be concluded that NSP has many central depressant-like activities.

Acetylcholine

The effect of antihistamine drugs on the neuroleptic-induced catalepsy.

The effect of atropine on the spiperone- or reserpine-induced catalepsy was compared with the effect pure antihistamines (chlorcyclizine, diphenhydramine, mepyramine) and antiserotonin -- antihistamine drugs (cyproheptadine, danitracen). All the drugs were used in equipotent doses in respect of their central cholinolytic action, assassed previously on the basis of the tremorine test. The potency of the antiserotonin action of chlorcyclizine, diphenhydramine and mepyramine was estimated by assessing the ID50 values of these compounds in the test based on antagonism to L-5-hydroxytryptophan action in the mouse. The spiperone-induced catelepsy, was most effectively inhibited by classical histaminolytics and less by drugs of a combined antiserotonin and antihistamine action. For the reserpine-induced catalepsy, differences in action of the two groups of drugs were less distinct. In both cases atropine produced the weakest anticataleptic effect. Amodiaquine, an inhibitor of histamine degradation, enhanced the catalepsy induced by either neuroleptic (the reserpine-induced catalepsy in a statistically significant menner). A possibility that the anticataleptic action of chlorcyclizine, cyproheptadine, diphenhydramine, mepyrymine and danitracen depends on the blockade of the histamine receptors in the brain is discussed.

5-Hydroxytryptophan

[Pharmacological studies of 4-ethoxy-2-methyl-5-morpholino-3(2H)-pyridazinone (M73101). (5) Action of M73101 on the central nervous system (author's transl)].

M73101 decreased spontaneous locomotor activity in both mice and rats and prolonged sleeping time induced by hexobarbital in mice. There was no evidence of cataleptogenic action, anti-tremorine action and antagonistic effect on reserpine-induced hypothermia in mice. M73101 did not inhibit convulsions induced by maximal electroshock and pentylenetetrazol but slightly inhibited the convulsion induced by strychnine in mice. Moreover, M73101 depressed only the monosynaptic action potential in intact and spinal cats, indicating that this compound exerts an inhibitory action on spinal function. On the EEG of rabbits, M73101 produced an arousal pattern in the spontaneous EEG and inhibited the recruiting response, but had no marked influence on the EEG arousal response, augmenting response and hippocampal afterdischarge. The arousal pattern in the spontaneous EEG induced by M73101 and the inhibitory action of this compound on the recruiting response were absent in the cerveau isolé preparation of the rabbit, indicating that M73101 may stimulate the brainstem reticular formation and that the inhibition of recruiting response may be related to the stimulatory effect. These properties of M73101 on the central nervous system are similar to those seen with aminopyrine though the potency was weaker. M73101 like aminopyrine showed no marked activity on the motor function.

Aminophylline

Some aspects of the neuropharmacology of phenylurea.

The neuropharmacology of phenylurea was studied. The compound is a potent sedative hypnotic agent with a fairly good margin of safety. It produced significant motor incoordination and behavioral changes in sub-sedative doses, thus suggesting that it acts on the areas of the brain which control motor coordination (neurological deficit) and spontaneous motor movements (awareness of environment). The activity pattern of phenylurea as measured on the rotarod treadmill was identical with that of an ataractic drug, meprobamate, and different from that of the sedative drug, 2-ethylcrotonylurea (ectylurea). It exhibited significant meprobamate-like antistrychnine (myorelaxant) activity, and at high doses only, anticonvulsant activity (pentetrazole antagonism). Phenylurea also protected mice against tremorine-induced tremors. A sub-sedative dose of phenylurea significantly prolonged pentobarbital sleeping time.

Animals

Syntheses and primary pharmacological screening of tandamine and related tetrahydrothiopyranoindoles with potential antidepressant properties.

A series of novel 1,3,4,9-tetrahydro-1-methyl-thiopyrano-[3,4-b]indole-1-ethanamines has been synthesized and examined for effects on reserpine-induced ptosis and reserpine-induced hypothermia in mice. One member of the series, the 9-ethyl-N,N-dimethyl derivative V (tandamine), was selected for further studies in regard to its possible use as an antidepressant agent. Tandamine has been resolved, and the levorotatory enantiomer was found to be more active than the racemic compound. The N-desmethyl derivative XIII, a metabolite of tandamine, has been prepared. The 5-ethyl-1,3,4,5-tetrahydro-N,N,1-trimethylthiopyrano[4,3-b]indole-1-ethanamine XXI, an analog of tandamine with the isomeric ring system, has also been synthesized and evaluated. In the primary pharmacological screening and in the drug-interaction studies with reserpine, tetrabenazine, and tremorine, tandamine was compared to the clinically effective tricyclic antidepressants--desipramine, imipramine, and amitriptyline. Tandamine was more effective than these agents in several screening procedures indicative of potential antidepressant activity.

Alkylation

Tremor: role of striatal cholinergic neurons and the effect of intrastriatal kainic acid.

Rats injected intrastriatally with kainic acid (KA) showed increased tremor responses to arecoline and tremorine, but not to harmaline. Since KA significantly reduced both pre- and postsynaptic measurements of cholinergic function in the striatum, the results indicate that integrity of the striatal cholinergic system is not essential to tremor response. Further investigations of cholinergic function in the brains of rats injected with KA did not reveal evidence of cholinergic supersensitivity; thus, the altered responses to cholinergic agents may reflect KA-associated destruction of some pathway normally opposing the behavioral output of cholinergic stimulation. If, as recently proposed, intrastriatal injection of KA produces an animal model of Huntington's disease (HD), then these results may also be relevant to experimental therapeutics of this disorder.

Animals

Anti-convulsant effect of phthalazino-2,3b-phthalazine-5(14H),12(7h)-dione (L-5418). I. Behavioral effect.

Since it had been demonstrated that L5418 has an anti-convulsant effect with no relation to its anti-inflammatory properties, comparative studies were carried out with the use of currently available anti-convulsant agents as controls. L-5418 inhibited tonic convulsions induced by maximal electroshock and strychinine in mice and prevented animals from the death sequence. L-5418 had an inhibitory effect on tonic convulsions induced by pentetrazol and N-sulfamoyl-hexahydroazepine (SaH 41-178), but not on clonic convulsions by those compounds at even a high dosage or on clonic convulsions induced by picrotoxin and bemegride. Trimethadione produced an inhibitory effect on both tonic and clonic convulsions. The hypnotic agents, phenobarbital and glutethimide inhibited both convulsions, but a higher dose was required in the case of clonic convulsions. Anti-convulsant agents are classified into three different groups according to their mode of action. L-5418 had the same mode of action as seen with diphenylhydantoin and carbamazepine. As L-5418 did not inhibit tremor induced by tremorine, an anti-Parkinson effect was ruled out. When L-5418 was administered alone, the animals did not lose the righting reflex nor show muscle relaxation observed in inclined screen and rotarod tests. Moreover, the compound had no influence on the aggressive behavior induced by electrical stimulation or olfactory bulb ablation. L-5418 possesses a selective anti-convulsant effect, yet has no sedative, tranquilizing or disturbing effects on movement such as equilibrium disturbance or muscle relaxation. L-5418 may prove useful for grand mal epilepsy as it is less toxic than diphenylhydantoin and carbamazepine.

Aggression

[Central action of WA-335-BS, a substance with peripheral antiserotonin and antihistaminic activity].

In rats and mice the serotonin and histamine antagonistic drug 9,10-dihydro-10-(1-methyl-4-piperidylidene)-9-anthrol (WA 335-BS) caused stronger central sedative effects than did cyproheptadine. WA 335-BS also displayed stronger activity against reserpine- and central tremorine-induced effects than did cyproheptadine and it slightly enhanced d-amphetamine-induced effects: therefore it may have antidepressant properties. WA 335-BS proved to be very effective against isolation-induced aggression in male mice. The comparatively small anxiolytic effects may have been caused in part by the central antiserotonin properties. Like cyproheptadine, WA 335-BS increased food consumption in cats. In EEG-experiments in the conscious rabbit the serotonin-antagonistic drugs WA 335-BS and cyproheptadine exerted stronger depressant activity on the arousal reactions than did the neuroleptic chlorpromazine. The results of our animal studies suggest WA 335-BS to be an antidepressant with sedative properties.

Aggression