Inhibition of amphetamine-induced locomotor activity by injection of carbachol into the anterior hypothalamic/preoptic area: pharmacological and electrophysiological studies in the rat

The effects of carbachol injected into the anterior hypothalamic/preoptic area on locomotion initiated by intra-accumbens injections of amphetamine were investigated. Changes of locomotion following intracerebral injections were measured in an automated activity box and the mean firing rate (m.f.r.) from neurons in the mesencephalic locomotor region (MLR) recorded in parallel acute electrophysiological experiments. Amphetamine (20.0 micrograms) injected to the nucleus accumbens caused a 2.5-fold increase in locomotion of rats. Subsequently, injections of carbachol (0.5 or 1.0 microgram) into the hypothalamic/preoptic area reduced the amphetamine-induced locomotion. These effects were stronger with ipsilateral than with contralateral injections and were reversed by pretreating the hypothalamic/preoptic area with 1.5 micrograms of atropine before carbachol injection. In electrophysiological experiments, injecting carbachol into the hypothalamic/preoptic area reduced the m.f.r. of MLR neurons from 8.3 +/- 0.7 to 4.1 +/- 0.5 per s and reduced the m.f.r. of 13 of 17 MLR neurons recorded continuously before and after injection. In contrast, injecting amphetamine into the nucleus accumbens increased the m.f.r. of units from 8.3 +/- 0.7 to 12.8 +/- 1.0 per s and increased the m.f.r. of 11 of 12 MLR neurons recorded continuously before and after injection. These results suggest that the hypothalamic/preoptic area contains muscarinic cholinoceptive areas which reduce locomotor activity by direct or indirect effects on the MLR.

Cueing effects of amphetamine and LSD: elicitation by direct microinjection of the drugs into the nucleus accumbens

Two groups of rats were trained to discriminate either d-amphetamine sulphate (AMPH; 1 mg/kg) or d-lysergic acid diethylamide bitartrate (LSD; 0.16 mg/kg). Microinjection of AMPH into the nucleus accumbens elicited a cueing effect which was similar to that of systemically administered AMPH in AMPH-trained animals (ED50 was 0.24 micrograms). Co-injection of (-)-sulpiride (50 or 100 ng) into the accumbens antagonized the effect of a fixed dose of AMPH (1 microgram) which, alone, produced 76% of the systemic AMPH cue effect. Microinjections of AMPH (1-5 micrograms) into either the anterior dorsomedial or the anterior ventrolateral striatum failed to elicit the cueing effect of AMPH. In LSD-trained animals a dose of 1 microgram LSD injected into the accumbens produced 84% of the systemic cueing effect of LSD. These results suggest that dopamine (DA) receptors in the nucleus accumbens are involved in AMPH discrimination. Furthermore, since both classical and atypical antipsychotic drugs block the AMPH cue, the results provide indirect evidence for involvement of mesolimbic DA in antipsychotic drug action.

Antagonistic behavioral effects of calcitonin and amphetamine in the rat

Using an automated testing apparatus, the hypermotility induced by amphetamine had previously been found to be inhibited by intracerebroventricular (ICV) administration of salmon calcitonin (CT). The present study used a computer-supported direct observational method to characterize further the interactions of CT and amphetamine. After treatment with amphetamine (1.5 mg/kg, IP), the incidence of rearing, nose poking, and locomotion was reduced in rats that were pretreated with 85 pmol salmon CT ICV; the incidence of sniffing and grooming remained unchanged. CT-induced dyskinesia, a unique consequence of central CT treatment, was attenuated but not abolished by administration of amphetamine. These results support the premise that a compound with receptor recognition characteristics similar to those of salmon CT may act as a neurotransmitter-modulator in the central nervous system.

beta-Endorphin involvement in the antidopaminergic effect of caerulein

Caerulein has been shown to possess a long-lasting antagonistic effect on amphetamine hyperactivity in rats when given in combination with haloperidol. We found that this effect of caerulein involved beta-endorphin. Naloxone pretreatment and hypophysectomy abolished the caerulein effect, while intracerebroventricular or intra-nucleus accumbens injection of beta-endorphin together with haloperidol administration produced an effect similar to that of caerulein. The results suggest that the long-term antagonism of the amphetamine effect of caerulein is mediated by the endogenous opioid beta-endorphin.

Blockade of amphetamine but not opiate-induced locomotion following antagonism of dopamine function in the rat

The effects of pharmacological blockade of dopamine (DA) receptors or 6-OHDA lesions of mesolimbic DA fibers on the locomotor-activating properties of systemic amphetamine (0.35 mg/kg) and heroin (0.5 mg/kg) were examined. Pharmacological blockade of DA receptors or lesions of mesolimbic DA neurons blocked amphetamine but not heroin-induced locomotion. These results show that the opiate receptors essential for opiate-induced locomotor activation are not located on mesolimbic DA neurons. It appears that DA plays a primary role in stimulant-induced locomotion, but may have only a secondary role in opiate locomotion.

Effects of low-level microwave irradiation on amphetamine hyperthermia are blockable by naloxone and classically conditionable

In a series of experiments, we investigated the effects of pulsed low-level microwave irradiation on amphetamine-induced hyperthermia in the rat. Rats were irradiated in a 2,450-MHz cylindrical waveguide exposure system at 1 mW/cm2, 2 mus pulses, 500 pps, average SAR of 0.6 W/kg. Acute (45 min) exposure to microwaves attenuated amphetamine-induced hyperthermia. This effect was blocked by pretreatment of the animals with the narcotic antagonist naloxone. In another experiment, rats were subjected to ten daily sessions of microwave exposure (45 min/session). On day 11, amphetamine-induced hyperthermia was studied in the animals immediately after a session of either microwave or sham exposure. Similar to the acute effect, amphetamine-induced hyperthermia was attenuated in rats irradiated with microwaves (unconditioned effect). In the sham-irradiated animals we observed a potentiation of the amphetamine-induced hyperthermia, which was a conditioned effect of microwaves. Thus, the conditioned effect (potentiation) was opposite in direction to the unconditioned effect (attenuation). No tolerance developed to the unconditioned effect after subchronic exposure. Furthermore, both conditioned and unconditioned effects of microwaves on amphetamine-induced hyperthermia could be blocked by treatment with naloxone. These data suggest that microwave irradiation may activate endogenous opioids, which in turn alter the actions of psychoactive drugs, and the effect of microwaves on drug action can be classically conditioned.

Study on the mechanism of the long-lasting antagonistic effect of caerulein on amphetamine-induced hyperactivity in rats

The long-lasting antagonistic effect of caerulein (CLN) on amphetamine (AMP) hyperactivity was abolished in rats following partial 6-OHDA lesions of the nucleus accumbens (NA) or dopamine (DA) A10 area. CLN showed the long-term antagonistic effect on AMP hyperactivity in rats following complete 6-OHDA lesions of the DA A9 area. Neonatal monosodium L-glutamate-treated rats did not show the CLN effect. These results suggest that opiate receptors presynaptically located on DA neurons in the NA and some modulatory changes in the beta-endorphin system in the arcuate nucleus may play an important role in producing the CLN effect.

Prazosin: effect on psychomotor-stimulant cues and locomotor activity in mice

Mice trained to discriminate 1 mg/kg d-amphetamine from saline, or the selective norepinephrine uptake inhibitor, nisoxetine, from saline, cross-generalized to the alternate drug. They also generalized to 5.6 mg/kg cocaine. The cues produced by amphetamine were antagonized by the selective alpha 1-adrenoceptor antagonist, prazosin, and slightly potentiated by the selective alpha 2-adrenoceptor antagonist, yohimbine. The nisoxetine cue was also antagonized by prazosin. In contrast, the peripherally acting sympathomimetics, p-hydroxyamphetamine and phenylpropranolamine, failed to substitute for, and pimozide and propranolol failed to block, either drug cue. In addition, prazosin, at a dose that did not affect either saline-associated locomotor behavior in mice or the locomotor-activity increase produced by the dopamine uptake inhibitor, bupropion, also antagonized the locomotor stimulation produced by amphetamine and cocaine. Thus, in mice, both the cues and locomotor stimulation produced by amphetamine and cocaine appear to be at least partially mediated by central alpha 1-adrenoceptor activation secondary to increased central synaptic concentrations of norepinephrine.

[Conditioned reactions of hippocampal neurons during amphetamine poisoning and its counteraction with haloperidol]

Activity of 144 neurones of the dorsal part of the rabbits hippocamp was recorded during elaboration of motor conditioned reflex to time. Chronic amphetamine intoxication lowered the ability of hippocampal neurones to form conditioned reactions in response to pairings of sound stimuli with electrocutaneous reinforcement and fully suppressed mechanisms of reproduction by cells of engrams of previous pairings in series of their omissions Single administration of haloperidol to intact animals somewhat increased the number of neurones reacting to the pairing and their omissions in conditioned reflex to time without significantly influencing the intensity and dynamics of reproduction of endogenous cellular reactions in the series of consecutive omissions of pairing. Haloperidol administration during amphetamine intoxication elicited shifts towards normalization of conditioned activity of neurones, eliminating the suppressing action of amphetamine on mechanisms of reproduction of engrams of combined stimuli. Such "therapeutic" effect of haloperidol in many cases did not depend on the character of its psychotropic action. The properties of amphetamine and haloperidol action on the cells of the hippocamp are discussed as compared to their action on the neurones of other brain structures, previously studied in an analogous experimental situation.

Effects of naloxone on heroin-, amphetamine- and caffeine-stimulated locomotor activity in the rat

We investigated the effects of naloxone on the locomotor activating properties of heroin (0.25 mg/kg SC), d-amphetamine (0.25 mg/kg SC) and caffeine (7.5 mg/kg SC). Naloxone eliminated heroin-stimulated locomotion at doses approximately six times lower than those that blocked amphetamine-stimulated locomotion. Caffeine-induced locomotor activation was insensitive to naloxone at all doses tested. These results suggest that central opiate systems are differentially involved in the behavioral activation produced by heroin, amphetamine and caffeine.

Analysis of the long-lasting antagonistic effect of caerulein on amphetamine hyperactivity in rats

Caerulein (CLN), which is chemically related to cholecystokinin octapeptide (CCK-8) and produces a short-lasting pharmacological effect when administered peripherally, caused a long-lasting antagonistic effect on amphetamine (AMP) hyperactivity in rats when given in combination with haloperidol (HLP). Briefly, rats were treated with a combination of CLN (0.3-40 micrograms/kg, s.c.) and HLP (0.1 mg/kg, s.c.) and exposed to AMP on the first day. The animals became less sensitive to AMP for 24 hr to about 2 weeks depending on the CLN dose, according to measurements of their ambulatory activities in an open field or with an Animex activity meter at low sensitivity. Examination of the properties of this long-lasting effect revealed that: 1) in animals treated with CLN and HLP, but without AMP on the first day, the susceptibility to AMP was not influenced on the next day; 2) in substitution experiments, the antagonistic effect of CLN could be reproduced by higher doses of CCK-8 (160 micrograms/kg) but not by nonsulfated CLN; 3) in the regimen of the treatment schedule, HLP could be replaced by chlorpromazine or sulpiride, but not by alpha-blocking agents like phenoxybenzamine or yohimbine; 4) apomorphine, nomifensine and tranylcypromine could not substitute for AMP. Thus, injection of CLN together with HLP and AMP on the first day might be necessary to produce the long-lasting anti-AMP effect. The possible mechanism of this CLN effect is discussed.

Amphetamine stimulation of glutaminase is blocked by neuroleptics

The ability of several classes of neuroleptics to inhibit the activity of phosphate-activated glutaminase was studied in several brain regions. These agents decreased glutaminase activity only in the amygdala. Amphetamine elevated glutaminase activity in this region. This stimulation was not blocked by (-) butaclamol, but was blocked by (+) butaclamol, haloperidol, chlorpromazine or clozapine.

Opposite effects of sulpiride and metoclopramide on amphetamine-induced stereotypy

The effects of the atypical neuroleptic sulpiride (0-20 mg/kg s.c.) and the classical neuroleptic metoclopramide (0-4 mg/kg s.c.) on behaviours produced by D-amphetamine (0-5 mg/kg i.p.) were measured in a time-sampling observational paradigm in rats. Sulpiride had one clear dose-dependent effect: it enhanced amphetamine-induced stereotyped behaviours (repetitive head movements, sniffing down and some gnawing). In contrast, metoclopramide dose-dependently decreased amphetamine-induced stereotypy, locomotion, rearing, and sniffing up, and concurrently antagonized the suppression of lying down produced by amphetamine. Sulpiride's facilitatory effects on amphetamine-induced stereotypy follow a pattern previously observed for two other atypical neuroleptics: clozapine and thioridazine. This may be a common effect of atypical neuroleptics. Since these neuroleptics are antipsychotic, amphetamine-induced stereotypy appears to be a poor animal model for human psychoses. It is suggested that sulpiride's effects may be mediated through a preferential presynaptic versus postsynaptic action on dopamine neurons in the nigrostriatal bundle.

Effects of d,l-propranolol on open field behavior of rats

Rats were administered with different doses of d,l-propranolol or d,l-propranolol plus amphetamine before open-field observations. Results show that d,l-propranolol decreased locomotion and rearing frequencies and increased immobility duration in rats. An antagonism between the effects of amphetamine and d,l-propranolol on general activity of rats was also observed. Results are discussed in the light of a possible interference of the drugs with the activity of either noradrenergic neurons or mid-brain reticular formation.

[Synthesis and neurologic action of new 11-substituted 5H-dibenzo[b,e][1,4]diazepines]

The synthesis of the title compounds is described. The compounds are characterized by having no cataleptogenic effect and no antagonistic effect against amphetamine stereotypies in experimental animals. The pharmacological results of the rota-rod, spontaneous motility, aggression-test, hexobarbital-potentiation and antagonism to physostigmine are reported.

[Model of the defense reaction in rats to study the antifenamine effect of neuroleptics for demonstrating their specific action]

The authors studied the ability of neuroleptics to eliminate the amphetamine-induced (5 mg/kg) disorders of the transformation of the defense response trajectory in rats kept in a U-shaped maze. Haloperidol (0.1 mg/kg) and clozapine (2 mg/kg) similarly normalized the animals' behavior but differently affected the motor automatisms typical for amphetamine stereotypy. Metoclopramide (1 mg/kg) reduced the external manifestations of amphetamint stereotypy but did not abolish the disorders in the defense response. It is likely that the ability of the neuroleptics to produce an antiamphetamine action in experimental defense response with multiple transformation of the responses might characterize specific properties of the drugs belonging to the class under discussion.

Determination of functionally-relevant serum levels of MJ 13859-1 in the dog: relationship to blockade of amphetamine stereotypy

The ability of drugs to block dopamine-agonist induced stereotypy in animals has proven to be a reliable in vivo predictor of antipsychotic efficacy in man. Assessment of a drug's potency at displacing [3H]spiperone from rat striatal membranes is an in vitro test which also has predictive validity for antipsychotic actions. Methods are described for assessing stereotyped behavior in the dog, and for measuring the ability of serum samples taken from treated animals at behaviorally interesting time points, to displace [3H]spiperone from washed synaptic membranes of rat striata. In these studies, oral administration of the potential antipsychotic agent MJ 13859-1 blocked amphetamine-induced stereotyped behavior in the dog for 6 hours. This behavioral effect was accompanied by sustained serum levels of [3H]spiperone displacing moieties derived from MJ 13859-1.

[Compounds with psychotropic activity. VIII. Synthesis and sedative activity of various 9-substituted derivatives of 5-phenylpyrrolo[2,1-d][1,5] benzothiazepine and cis-4,5-dihydro-4-hydroxy-5-phenylpyrrolo[2,1-d][1,5]benzothiazepine]

Syntheses of 9-chloro-, 9-trifluoromethyl- and 9-methoxy-5- phenylpyrrolo [2,1-d] [1,5] benzothiazepine [II a-c] and of cis-9-chloro- and cis-9-trifluoromethyl-4,5-dihydro-4-hydroxy-5- phenylpyrrolo [2,1-d] [1,5] benzothiazepine with the respective acetyl derivatives (III a-d), according to previously restated routes, are described. The sedative activity was tested against the anti-amphetamine activity in the rat. The 1-[5-trifluoromethyl-2-(alpha- hydroxycarbonylbenzyl ) thiophenyl + ++]-pyrrole ( NF34 ) and the pyrrolo [2,1-d] [1,5] benzothiazepine -5-carboxamide ( NF44 ) showed sedative activity similar to that of diazepam.

Behavioural correlates to the dopamine D-1 and D-2 antagonists

The acute dopamine (DA) receptor blockade of neuroleptics can be demonstrated in mice by antagonism of stereotypies induced by the DA-agonist methylphenidate and in rats by antagonism of stereotypies induced by the DA-agonists amphetamine or apomorphine. Neuroleptics such as the thioxanthene, cis(Z)-flupentixol, the phenothiazine, fluphenazine, the butyrophenone, haloperidol and the benzamide clebopride are equipotent behaviourally as well as clinically. Also the D-1 receptor-antagonist SCH 23390 has the same pharmacological effects. In a series of experiments where the methylphenidate-induced stereotyped gnawing in mice was inhibited by neuroleptics it was shown that the effect of butyrophenones was greatly attenuated by concomitant treatment with scopolamine and diazepam. Similar results were obtained in rats experiments. The effect of phenothiazines was less influenced and that of thioxanthenes and SCH 23390 remained nearly unchanged. Besides, a clear differentiation of these drugs was seen when they were tested in mice rendered supersensitive by 12 days treatment with different neuroleptics. In the withdrawal phase the decrease effects against methylphenidate were shown by increased ED50 values for methylphenidate antagonism and an increased response to methylphenidate. The thioxanthenes and SCH 23390 retained the ability to antagonize the stereotyped gnawing, the phenothiazines showed a reduced effect, whereas the butyrophenones showed both tolerance and cross tolerance to the stereotyped behaviour. This behavioural classification of neuroleptics into three different groups is comparable with the classification obtained by DA-receptor binding techniques in vitro.

Caffeine reduces amphetamine-induced activity in asymmetrical interaction

Caffeine-amphetamine interactions were studied to determine whether attenuation of amphetamine-induced activity by caffeine pretreatment (30 mg/kg) is the result of increased or decreased sensitivity to amphetamine. Caffeine pretreatment attenuated amphetamine activity in the rats without producing a horizontal shift in the dose-response curve. Results support a reduction in sensitivity to amphetamine. A cross-tolerance design revealed an asymmetrical interaction between caffeine and amphetamine. Multiple caffeine treatments (30 mg/kg) produced tolerance and attenuation of subsequent amphetamine activity (1.5 mg/kg). Amphetamine did not produce tolerance or affect subsequent caffeine-induced activity.

gamma-Butyrolactone effects on behavior induced by dopamine agonists

gamma-Butyrolactone (GBL) potently inhibits stereotyped behavior induced by indirect (amphetamine and methylphenidate) and direct (apomorphine) dopamine agonists. Amphetamine induces a dose-response partial reversal of the GBL effect. The GABA antagonist, bicuculline, only partially reverses the GBL inhibition of apomorphine activity, indicating that GBL may be acting through mechanisms in addition to effects on GABA.

Neuroleptic activity and dopamine-uptake inhibition in 1-piperazino-3-phenylindans

A series of 1-piperazino-3-phenylindans was synthesized and tested for neuroleptic and thymoleptic activity. Neuroleptic activity was found only in trans racemates and was associated with one of the enantiomers only. The potent and long-acting neuroleptic compound trans-4-[3-(4-fluorophenyl)-6-(trifluoromethyl)indan-1-yl]-1-piperazineethanol (Lu 18-012, tefludazine) was developed by systematic variation of structural components. Thymoleptic activity was optimized, especially with respect to dopamine-uptake inhibition. No geometrical stereoselectivity was found with regard to dopamine-uptake inhibition, but a high enantioselectivity could be demonstrated for both cis and trans racemates. The most potent compounds were 1-piperazino-3-(3,4-dichlorophenyl)indans with IC50 values of about 2nM for inhibition of dopamine uptake.