Interaction of LSD and other hallucinogens with dopamine-sensitive adenylate cyclase in primate brain: regional differences

The influence of D-lysergic acid diethylamide (LSD) and mescaline on adenylate cyclase activity was studied in homogenates of Cebus and rhesus monkey anterior limbic cortex (ALC), frontal cortex (FC), caudate nucleus and retina. Previous studies have shown these tissues to contain dopamine-stimulated adenylate cyclase (AC). In addition, we are now reporting the presence of a dopamine-sensitive adenylate cyclase in the auditory cortex. AC of ALC and auditory cortex was stimulated by LSD and mescaline, whereas activity of FC, caudate nucleus and retina was not stimulated by the same agents. In contrast to regional specificity for stimulation, LSD was capable of antagonizing dopamine-stimulated activity in all brain regions examined. LSD and mescaline produced similar maximal stimulation (about 70%) of AC of ALC homogenates, but the EC50 for LSD (0.43 micrometer) was about one-tenth that for mescaline (4.5 micrometer). Similar relative potencies were also observed for the auditory cortex enzyme. Although much weaker than LSD, methamphetamine also produced a dose-dependent stimulation of ALC AC. Both agonist and antagonist effects of the hallucinogens appear to involve interaction with dopamine receptors; LSD- or methamphetamine-stimulated activity in ALC was blocked by haloperidol and fluphenazine, which are dopamine antagonists, but not by phentolamine, an alpha-receptor blocker. Antagonism of dopamine by LSD in both ALC and FC was found to be competitive and mescaline was an effective but weaker antagonist than was LSD. In addition, neither histamine--nor Gpp(NH)p--stimulated activity of FC was inhibited by LSD. It is proposed that the occurrence of dopamine agonistic action of hallucinogens in only certain regions of primate brain may provide a basis for at least some of the behavioral effects of LSD, mescaline and methamphetamine in primates.

Mescaline increases startle responding equally in normal and raphe-lesioned rats

To test the possible involvement of serotonin-containing cells of the midbrain in mediating the effects of mescaline on startle responding, electrolytic lesions were made in either the dorsal or median raphe nucleus in rats. Decreases in either striatal or hippocampal tryptophan hydroxylase activity confirmed the effectiveness of the lesions. One week later, startle was measured in response to 30 air-puff stimuli for each rat. Median, but not dorsal, raphe lesions increased startle magnitudes throughout the test session. The following day each group was divided into matched halves and were given 60 trials, 30 minutes after intraperitoneal injection of either saline or 10 mg/kg mescaline. Despite the large differences in baseline startle among the groups, mescaline produced comparable 25% increases in startle magnitudes in both sham- and raphe-lesioned animals. This result fails to support the hypothesis that increased startle responding produced by mescaline is mediated by the midbrain raphe nuclei.

Severe aggression in rats induced by mescaline but not other hallucinogens

Pairs of male Sprague-Dawley rats were administered mescaline, lysergic acid diethylamide (LSD), psilocin, N,N-dimethyltryptamine (DMT), 3,4-dimethoxyphenylethylamine (DMPEA), or 5-hydroxydopamine (5-OHDA) IP prior to being placed in a shock-elicited aggression situation. When foot shock was delivered, controls struck each other with their forepaws, but never engaged in either biting or injurious fighting. Mescaline-treated rats (50 or 250 mg) rarely struck each other, but engaged in nearly lethal biting. While LSD (25--400 micrograms/kg), psilocin (2.0 mg/kg), and DMT (5 mg/kg) produced some biting, this did not significantly differ from controls and never resulted in injuries. At higher doses, psilocin, DMT, and DMPEA decreased the amount and intensity of fighting. Rats treated with 5-OHDA (8--200 mg/kg) or LSD (25--400 micrograms/kg) did not differ from controls. These results suggest that mescaline's ability to induce pathological aggression in rats exposed to foot shock is not shared by other hallucinogens or nonhallucinogenic mescaline analogues.

[Pharmacologic analysis of hierarchical relationships in mice]

In experiments on mice (put in triads and tetrads) stable domination-subordination relations (DS) of predominantly despotic type were formed. The experiments were staged in specially designed communicating populational cages. Pharmacological evidence of inertness of DS relations in small groups of mice is presented. Critical factors of DS inertness are examined. It is shown that psychotropic drugs of different classes have difficult effect on the maintainance of DS inertness. Prolonged administration of psychotropic drugs suppressing the dominant's aggression may result in DS inversion.

The effects of lysergic acid diethylamide and mescaline-derived hallucinogens on sensory-integrative function: tactile startle

Tactile startle responding by male Sprague-Dawley rats given 60 presentations of air-puff stimuli (37.5 psi) was measured after the intraperitoneal administration of graded doses of hallucinogens and other psychoactive drugs. Among the drugs tested were the indoleamine-derived compounds, lysergic acid diethylamide (LSD), N,N-dimethyltryptamine and psilocin, and the phenylethylamine-derived compounds, mescaline, 2,5-dimethoxy-4-methylamphetamine and a series of active and inactive congeners of 2,5-dimethoxy-4-methylamphetamine. All of the active phenylethylamines increased startle response magnitudes throughout the test session. This pattern of augmented startle suggests that these drugs increase reactivity. However, none of the indoleamine hallucinogens increased startle responding. Of the nonhallucinogenic drugs tested, only apomorphine increased startle responding, while clonidine significantly decreased it, and amphetamine, chlorimipramine, scopolamine and methysergide had no effect. In additional studies with LSD, it was found that LSD increased the response to only the first stimulus when more intense air-puffs were used (50 psi). Furthermore, when the number of stimuli was increased from 60 to 240 (1 hr) so that appreciable habituation was evident in controls, LSD impaired this habituation. Whereas the response magnitudes of the control group decreased by 70% across the session, the responses of LSD-treated rats decreased by only 32%. These results suggest that LSD and phenylethylamine-derived hallucinogens may differ in their effects on tactile startle responding.

[Psychopharmacological effects of flutazolam (MS-4101) (author's transl)]

Behavioral effects of Flutazolam (MS-4101), a new derivative of benzodiazepines, was investigated and compared with effects of diazepam in mice and rats. MS-4101 suppressed hyperemotionality in septal rats, fighting behavior in long-term isolated mice and pentylenetetrazol convulsion and potentiated thiopental sleep. These effects of MS-4101 were the same in potency as those of diazepam. MS-4101 was more potent than diazepam in reducing the spontaneous locomotor activity in the open-field test and potentiating the stimulant effect of methamphetamine on locomotor activity. On the other hand, suppression of hyperemotionality in O. B. rats, potentiation of ethanol-induced anesthesia, prevention of maximal electroshock, prevention of strychnine convulsin and muscle relaxant effect of MS-4101 were less potent than in the case of diazepam. MS-4101 had also an anticonflict effect, which was less potent than that seen with diazepam. Suppression of locomotor activity was potentiated by chronic administration of MS-4101, but disappeared with chronic administration of diazepam. MS-4101 inhibited considerably both scratching and head-twitch induced by mescaline in mice. Scratching was increased with small doses of diazepam and decreased with high doses. Head-twitch was decreased with small doses of diazepam and increased with high doses.

[Effects of mescaline and lysergide on the mechanical responses of isolated organs of the rat to catecholamines and the role of calcium transfers in these phenomena]

On isolated Rat vas deferens the contracting responses of noradrenaline and dopamine are increased by mescaline (23 micromoles) and decreased by lysergide (15 micromoles). Similarly, on isolated Rat duodenum previously decalcified the hypertonic responses of recalcification are modified in the opposite direction by the two agonists. On the other hand, mescaline such as lysergide increase the fall of tonus which ensues the decalcification of isolated duodenum.

Mescaline produces pathological aggression in rats regardless of age or strain

Several measures of aggressive behavior were investigated in three ages (40-50, 90-110, and 180-200 days old) and in three strains (Sprague-Dawley, Wistar, and Long-Evans) of rats before and following the administration of mescaline hydrochloride in a shock-elicited aggression situation. The measures included the number of fights, duration of fighting, latency of fighting, number of bites inflicted, and a composite index of pathological aggression. During predrug baseline testing it was found that older rats, regardess of strain, engaged in more frequent fights that were longer in duration and more intense than younger animals. When the animals were tested with mescaline, they engaged in significantly more fights, biting, and pathological aggression than during baseline testing regardless of their age of strain. These results suggest that mescaline-induced pathological aggression in rats is a robust phenomenon.

Preliminary studies of the sodium borohydride stabilizable binding of phenylethylamine and tyramine to brain preparations

The borohydride stabilizable binding of 2-phenylethylamine and p-tyramine to mouse brain homogenates was compared to that of tryptamine and of serotonin. The highest binding was found to be that of tryptamine, followed by that of serotonin, tyramine, and phenylethylamine. The stabilizable binding of phenylethylamine to calf midbrain (including corpus striatum) homogenates and synaptic membranes was decreased by dopamine; this amine and D-amphetamine also decreased the stabilizable binding of tyramine to rat brain homogenates. The subsynaptosomal distribution of the binding of phenylethylamine to synaptic calf midbrain fractions was also investigated. The highest binding capacity was found in the 0.8 M fraction, rich in myelin.

6-Hydroxydopamine inhibits some effects of mescaline centrally administered to rabbits

The narcotic antagonist naloxone does not antagonize antinociception elicited in the rabbit by 100 microgram/kg of mescaline centrally administered, whereas pretreatment with 6-hydroxydopamine (6-OHDA) inhibits this mescaline effect. Stereotyped behavior of rabbits following central mescaline administration is also prevented by 6-hda pretreatment. Since 6-OHDA in known to produce a degeneration of catecholamine containing nerve terminals, a crucial role of catecholamines is suggested in the complex of effects seen in the rabbit after central administration of the hallucinogen.

3H-metaraminol releasing action of mescaline from rat hypothalamus in vitro

The amine releasing action of mescaline was investigated in rat isolated hypothalamus labeled with 3H-metaraminol. Mescaline had no effect on the uptake of 3H-metaraminol but produced its release in a concentration-related manner. 4 x 10(-4) M mescaline, which produced submaximal effects was used for subsequent experiments. 3 x 10(-5) M cocaine had no effect on the 3H-metaraminol releasing action of mescaline. Mescaline was fully effective in Ca2+-free medium while 6 x 10(-2) M KCl was ineffective. 3 x 10(-7) M tetrodotoxin or 6 x 10(-5) M lidocaine partially blocked mescaline-induced release but substantially or completely blocked 3 x 10(-2) M KCl-induced release. Prior exposure of hypothalamus to 3 x 10(-4) M tyramine reduced the releasing action of mescaline. Thus, mescaline appears to release 3H-metaraminol both by Ca2+-independent (tyramine-like) and Ca2+-dependent (lidocaine-sensitive) mechanisms. 3 x 10(-4) M tyramine and 6 x 10(-2) M KCl released 14C from control hypothalamus labelled with 14C-mescaline, but not from reserpinized hypothalamus. The amounts of 14C recovered in 14C-mescaline labeled control and reserpinized hypothalamus at the end of 50 min of efflux were similar suggesting a poor retention of 14C-mescaline by storage particles.

Pharmacological and behavioral components of tolerance to LSD and mescaline in rats

A fixed-ratio schedule of water reinforcement (FR-10) was used to examine the relative contributions of pharmacological and behavioral mechanisms in the development of tolerance to the disruptive effects of LSD and mescaline in the rat. Rats treated daily with LSD or mescaline before operant testing developed tolerance to the impairement of responding, while rats treated daily after each session did not display tolerance when the drugs were administered before testing. These results indicate that behavioral compensatory mechanisms may be involved in the development of tolerance to the disruptive effects of LSD and mescaline on fixed-ratio (FR-10) performance.