The role of central serotonergic mechanisms on head-twitch and backward locomotion induced by hallucinogenic drugs

Head-twitch induced by lysergic acid diethylamide, mescaline and 2,5-dimethoxy-4-methylamphetamine (DOM) was significantly increased by medial raphe (m-R) lesions, but dorsal raphe (d-R) lesions did not produce any changes. Hallucinogen-induced head twitch was inhibited by methysergide and tended to be increased by PCPA. These results suggest that 5-HT receptors innervated with the ascending 5-HT pathway originating in the m-R play a vital role in the manifestation of hallucinogen-induced head-twitch. That is, increase of head-twitch is ascribed to supersensitivity of 5-HT receptors. On the other hand, DOM-induced backward locomotion was inhibited by m-R or both dorsal and medial raphe lesions and methysergide, and was reversed to forward locomotion, differently from the hallucinogen-induced head-twitch. A reversion of backward locomotion was not obtained with d-R lesions or PCPA treatment.

Inescapable shock alters mescaline's disruption of active avoidance acquisition

Rats were tested on a two-way avoidance acquisition with or without inescapable shock given 24 h prior to training. Mescaline given to nonshock rats disrupted acquisition in a dose-dependent fashion and tolerance developed to this disruption. Mescaline given to shock rats had no effect on acquisition even though levels of acquisition were the same for both shock and nonshock rats without drug. Moreover, subchronic treatment (5 days facilitated acquisition. These experiments demonstrate an interaction between shock, which presumably is a stressor, and mescaline. The data are consistent with the observation that when animals are exposed to presumptive stressors (e.g., shock, handling) hallucinogens can facilitate behavior, while in other situations, hallucinogens disrupt behavior.

The integrity of the social hierarchy in mice following administration of psychotropic drugs

1 Mice in small groups develop a despotic type of social hierarchy, a feature of which is to resist alteration through the medium of psychotropic drugs. This makes a rapid pharmacologically induced change in the social hierarchy impossible. 2 Patrolling the territory and a certain level of social interaction are both critical factors in maintaining the phenomenon of inertia in the social hierarchy. Psychotropic drugs (diazepam, droperidol and mescaline) altered both these factors to a varying degree and also displayed a differing ability to maintain the inertia of the social hierarchy. 3 A drug-induced alteration in the level of aggression in a subordinate mouse in a group of three does not cause an alteration in its social position. 4 Chronic administration of diazepam, droperidol or mescaline, all of which alter the level of aggression in different ways, can result in an inversion of the social hierarchy where a competitive rival is present in the group of mice. The rate of inversion of the social hierarchy depends on the type of pre-existing social hierarchy. 5 It is suggested that the ability of psychotropic drugs to maintain the inertia of the hierarchy be used as an index of their effect upon certain types of species-specific behaviour; in particular aggression.

Naloxone potentiates the disruptive effects of mescaline on operant responding in the rat

Food-deprived male rats were trained to press a lever on a fixed ratio-40 (FR-40) operant schedule for food reinforcement. Administration of mescaline (4.0--10.0 mg/kg) immediately before the start of the operant session resulted in a cessation of responding for some portion of the 40-min period ("hallucinatory pause"). The duration of this pause was found to be dose-dependent. Although administration of naloxone alone (1.0-8.0 mg/kg, five minutes prior to the start of the session) had no effect on FR-40 responding per se, pretreatment with this agent significantly potentiated the disruptive effects of mescaline. This potentiation by naloxone was further shown to be dose-dependent. These data suggest that the effects of the phenethylamine hallucinogen mescaline are potentiated by pretreatment with the narcotic antagonist naloxone.

LDS-25 as a discriminative stimulus for response selection by pigeons

Pigeons (N=4) were trained to discriminate between the effects induced by intramuscular (IM) injections of d-LSD and saline using a discrete-trial discrimination paradigm (choice between left and right hand key) in a conventional operant box. The solutions were administered IM 15 min prior to the sessions. A FR 15 schedule was in operation to produce food. Which of the two keys was correct on a given training session depended upon whether LSD or saline had been given. Three of the birds were trained and maintained with a dose of 40 microgram/kg of LSD and the fourth pigeon finally was maintained on 50 microgram/kg of LSD. The dose resulting in 50% LSD appropriate responding (ED50) was 18 microgram/kg and the median time-interval for the decay of the LSD stimulus (40 microgram/kg) was 84 min. Tests with psilocybin (ED50=0.55 mg/kg) and N,N-dimethyltryptamine (ED50=5.7 mg/kg) resulted in responding appropriate for the LSD training condition. Mescaline injections above 10 mg/kg severely suppressed responding. The few responses emitted after tests with 15 and 20 mg/kg of mescaline were directed to the LSD associated key. Tests with BOL (0.1 to 3 mg/kg) as well as three other psychotropic drugs (delta 9-tetrahydrocannabinol, morphine and, pentobarbital) did not result in responding above 50%) LSD appropriate responses. As a possible antidote, methergoline, a pubetative antagonist of post-synaptic serotonin receptor sites, was administered 75 min prior to testing the cueing properties of LSD. No definitive role for a blocking effect of the LSD-cue is provided by the present data.

Cumulative alterations in rat behavior during continuous administration of LSD or mescaline: absence of tolerance?

Male hooded rats were observed for 6 days following implantation with slow-release subcutaneous pellets containing LSD, mescaline, or control vehicle solution. In animals housed in isolation cages, continuous hallucinogen administration resulted in a gradual increase in head twitches and catatonic postures which peaked 3--4 days after pellet implantation and then declined. In animals housed in social colonies, there were also delayed increases in behavior following hallucinogen-pellet implantation, but these principally involved social behaviors such as fighting by mescaline-treated animals and social grooming by LSD-treated animals. This finding of gradual and cumulative effects of continuous hallucinogen administration contrasts with the usual finding of a rapid tolerance to hallucinogens following repeated injections.

EEG effects of hallucinogens and cannabinoids using sleep-waking behavior as baseline

Three hallucinogens (d-lysergicacid diethylamide (LSD), mescaline, psilocybin) and two cannabinoid derivatives (tetrahydrocannabinol (THC), synhexyl) were tested for their long-term effects on the EEG of the cat. The drug-induced alterations in the EEG frequency spectrum were "drug-specific" in the sense that they would be statistically unlikely to occur during sleep-waking behavior. The two classes of compounds produced distinctly different EEG effects which were remarkably similar within each class. The duration of activity and relative potencies were consistent with those obtained by other measures, both in cats and in other species including man.

Following several days of continuous administration d-amphetamine acquires hallucinogenlike properties

Rats injected with LSD or mescaline show the behavioral syndrome which has been previously reported following injections of hallucinogens in higher mammals: limb flicks and whole body shakes. Although these behaviors are not elicited by acute injections of amphetamine, they are present in rats which have been pretreated for 108 h with a slow-release amphetamine pellet, given a 12 h rest period, and then injected with d-amphetamine. Such pellet-pretreated animals also groom their body surface excessively. We propose that this novel syndrome which follows continuous amphetamine administration can serve as an animal model of the type of amphetamine psychosis that is produced by a similar drug regimen in humans.

The discriminative stimulus properties of 2,5-dimethoxy-4-methylamphetamine (DOM): differentiation from amphetamine

Rats were trained in a two-lever operant procedure to discriminate either 1.0 mg/kg (+)amphetamine or 1.5 mg/kg DOM from saline. Rats trained to discriminate DOM from saline showed generalization with the DOM training condition when tested with mescaline or 2,5-dimethoxy-4-ethylamphetamine (DOET), but not when tested with (+)amphetamine or methylphenidate. Both isomers of DOM generalized with racemic training compound, the (-)isomer being more potent. The DOM stimulus was completely blocked by the serotonin (5-HT) antagonists cinanserin and methysergide, but not by the peripheral 5-HT antagonist xylamidine nor the dopamine antagonist haloperidol. Rats trained to discriminate (+)amphetamine from saline generalized with the amphetamine training condition when tested with methylphenidate but not when tested with mescaline, DOET, racemic DOM, or either isomer of DOM. The amphetamine stimulus was blocked by pretreatment with haloperidol but not by cinanserin, methysergide, or xylamidine. The results show that, despite their structural similarity, amphetamine and DOM induce pharmacologically distinct stimuli.

In vivo evidence of partial agonist activity exerted by purported 5-hydroxytryptamine antagonists

Using a food-reinforced two-lever operant method, rats (n = 9) were trained to discriminate 0.16 mg/kg LSD from saline. Tests for stimulus generalization in rats so trained indicated that the purported 5-HT antagonists cyproheptadine (1.25 and 10 mg/kg), methysergide (0.16 to 10 mg/kg) and mianserin (2.5 to 40 mg/kg) produced partial generalization with LSD. The hallucinogens mescaline (5 to 40 mg/kg) and quipazine (1.25 to 5 mg/kg) were also generalized with LSD. The data suggest that cyproheptadine, methysergide and mianserin may produce partial agonist effects in addition to their antagonist action at central 5-HT receptor sites.

Stimulation of human prolactin secretion by mescaline

Prolactin (PRL) and Growth Hormone (GH) secretions were studied in human serum after the oral administration of 5 mg/kg mescaline (3,4,5-trimethoxy-beta-phenylethylamine) or 2,3,4-trimethoxy-beta-phenylethylamine (2,3,4-TMPEA) respectively. Mescaline stimulated the secretion of PRL more than four-fold above base-line levels. Peak concentrations were found 90--120 min after drug intake. Five hours later serum PRL was still markedly increased. Mescaline also triggered GH secretion. There was no alteration of serum PRL and GH concentrations after intake of the non-hallucinogenic 2,3,4-TMPEA.

[Effect of mescaline on cerebral cholinesterases and on exploratory behavior in rats]

In this study the Authors had the purpose to evaluate the action of a psychotomimetic substance (mescaline) on behavior (exploring behaviour and spontaneous motility) and on cerebral biochemistry (cholinesterase activity) of rat. The mescaline has shown to be active both on behaviour (increasing the spontaneous motility) and on biochemistry (decreasing the total cholinesterase activity). From the examination of the results of this work it could be cautiously assumed the hypothesis that the behavioural effects of mescaline are related (at least partially) to modifications of the cholinergic system at the cerebral level.

Neurolepticlike actions of l-methadone: effect on mescaline-induced altered behavior and on tissue levels of mescaline in mice

Mice were injected ip with either saline, l-methadone (2.5, 5, 20 mg/kg), perphenazine (1, 10, 15 mg/kg), or chlorprothixene (1.25, 2.5, 15 mg/kg) 30 min prior to mescaline-14C (25 mg/kg). Mescaline-induced behavioral changes such as agitation, excitement, slight increase in ventilation, and fright to sound stimuli were prevented by all doses of three drugs, and head-shaking, scratching, and locomotor-increasing effects by 5 and 20 mg/kg methadone and by all doses of both neuroleptics. Catalepticlike state and moderate to marked hypothermia induced by all doses of chlorprothixene, 10 and 15 mg/kg perphenazine, and 20 mg/kg methadone were not reversed by mescaline. Chlorprothixene (all doses), perphenazine (10, 15 mg/kg), and methadone (5, 20 mg/kg) caused marked retention of mescaline and its deaminated metabolite, 3, 4, 5-trimethoxyphenyl acetic acid in both brain and plasma. The fact that relatively higher doses of methadone than neuroleptics are needed to ensure effective antagonism to mescaline action tends to indicate a less specific interaction of the opiate with the neuroleptic/dopamine receptor proposed for central mescaline effects.

Molecular connectivity analysis of hallucinogenic mescaline analogs

The hallucinogenic (psychotomimetic) potency of 10 mescaline analogs was examined by molecular connectivity analysis. Potencies could be described by a two-term relating equation, which explained 94% of the variance in activity, on the basis of structural variation, 2,5-Dimethoxy substitution as well as the nature of the 4-position substituent played an important role in determining hallucinogenic potency. With the relating equation, reasonable potency predictions were made for six compounds not included in the initial investigation.

Effect of mescaline on an innate behaviour of mice

The action of mescaline on mice innate behaviour was studied. In the first experiment the drug modified the innate behaviour of mice. The dose-effect curve was obtained by the second. The results pointed out that, in the range of doses examined, there was one for which the disruptive action of mescaline reach the maximum so that mice behaviour became completely casual.

Effects of mescaline and amphetamine on simultaneous visual discrimination in two inbred strains of mice

The effects of mescaline and amphetamine were investigated in BALB/cJ (BALB) and C57BL/6J (C57) mice using the five-choice Yerkes--Thompson Bryant--Bovet-Nitti apparatus for patterns discrimination. Two sets of experiments were carried out. In the first set, pretrial administration of mescaline (5, 10, and 20 mg/kg) was followed by performance improvements in the C57 mice, while performances of the BALB strain were impaired by the treatment, as compared with those of the saline-injected (4 ml/kg) controls. The pretrial administration of amphetamine (0.1, 0.25, and 0.5 mg/kg) improved performances of both strains. In a second set of experiments, the same effects as in the pretrial experiments were observed in both strains following administration of mescaline (20 mg/kg) and amphetamine (0.5 mg/kg) immediately after each experimental session. No effect was evident when the drugs were injected 2 h after training, suggesting that effects of the pretrial treatments were due to influences of mescaline and amphetamine on the consolidation processes of the two strains of mice tested.