The effects of intracranial administration of hallucinogens on operant behavior in the rat. I. Lysergic acid diethylamide

Characterization of the discriminative stimulus properties of centrally administered (-)-DOM and LSD

Despite the plausible assumption that the effects of hallucinogens predominantly arise in the central nervous system, most studies of these drugs in intact subjects have been conducted following systemic administration. The objective of the present investigation was to characterize the stimulus effects of (-)2,5-dimethoxy-4-methylamphetamine ((-)-DOM) following intracerebroventricular administration. Chronic indwelling cannulae were implanted into the lateral ventricle of male Fischer 344 rats trained to discriminate systemically administered (-)-DOM or lysergic acid diethylamide (LSD) from saline. Time-course and dose-response relationships for (-)-DOM and LSD administered intracerebroventricularly were established. For both LSD and (-)-DOM, central administration did not change the pretreatment times required for the maximal stimulus effects to occur. However, the onset of the stimulus effect was more rapid following intracerebroventricular administration. Following pretreatment periods that maximize drug-appropriate responding, central administration of (-)-DOM and LSD was approximately 2.4- and 1.5-times more potent, respectively, than systemic administration. The results of this study are consistent with the assumption that the stimulus effects of (-)-DOM and LSD are centrally mediated.

Acute effects of LSD on rhesus monkey operant test battery performance

The acute effects of LSD were assessed in rhesus macaques using behavior in several complex tasks designed to model aspects of time estimation, short-term memory and attention, motivation, learning, and color and position discrimination. The end points monitored included percent task completed, response rate, and accuracy. LSD (0.0003-0.03 mg/kg intravenously) significantly decreased percent task completed and accuracy in the time estimation task at doses < or = 0.003 mg/kg, but did not significantly affect response rate in this task at any dose tested. Accuracy in the short-term memory task was significantly decreased at the highest dose tested (0.03 mg/kg), but no other end points were affected in this task. Response rate was decreased in both the motivation and learning tasks at doses (0.01 and 0.003 mg/kg, respectively) lower than those affecting other end points. In the color and position discrimination task, only response rate was affected (0.01 and 0.03 mg/kg). These data demonstrate that in rhesus monkeys, performance of tasks believed to depend on aspects of time estimation and motivation are more sensitive to the acute disruptive effects of LSD than are tasks thought to model learning, short-term memory, and color and position discrimination.

Clinical features and management of intoxication due to hallucinogenic drugs

Hallucinogenic drugs are unique in that they produce the desired hallucinogenic effects at what are considered non-toxic doses. The hallucinogenic drugs can be categorised into 4 basic groups: indole alkaloid derivatives, piperidine derivatives, phenylethylamines and the cannabinols. The drugs reviewed include lysergic acid diethylamide (LSD), phencyclidine (PCP), cocaine, amphetamines, opiates, marijuana, psilocybin, mescaline, and 'designer drugs.' Particularly noteworthy is that each hallucinogen produces characteristic behavioural effects which are related to its serotonergic, dopaminergic or adrenergic activity. Cocaine produces simple hallucinations, PCP can produce complex hallucinations analogous to a paranoid psychosis, while LSD produces a combination of hallucinations, pseudohallucinations and illusions. Dose relationships with changes in the quality of the hallucinatory experience have been described with amphetamines and, to some extent, LSD. Flashbacks have been described with LSD and alcohol. Management of the intoxicated patient is dependent on the specific behavioural manifestation elicited by the drug. The principles involve differentiating the patient's symptoms from organic (medical or toxicological) and psychiatric aetiologies and identifying the symptom complex associated with the particular drug. Panic reactions may require treatment with a benzodiazepine or haloperidol. Patients with LSD psychosis may require an antipsychotic. Patients exhibiting prolonged drug-induced psychosis may require a variety of treatments including ECT, lithium and l-5-hydroxytryptophan.

The effects of intracranial administration of hallucinogens on operant behavior in the rat. II. 2,5-Dimethoxy-4-methylamphetamine (DOM)

2,5-Dimethoxy-4-methylamphetamine (DOM) was infused into discrete brain regions of rats trained to press a bar for food reinforcement on a fixed ratio-40 (FR-40). Sites were chosen as major areas of the brain 5-hydroxytryptamine (5-HT) system: the dorsal and median raphe nuclei, dorsal hippocampus, lateral habenular nuclei and the prefrontal cortex. Following training in a fixed ratio-40 (FR-40) operant behavior rats were implanted with stainless steel cannulae into the brain area to be examined. Bilateral cannulae were implanted for the lateral habenular nuclei, dorsal hippocampus and the prefrontal cortex. Following recovery from surgery, DOM (20-300 micrograms) was tested on operant behavior by infusing the drug immediately before the operant session. Infusion of vehicle was inactive. DOM produced a dose-dependent decrease in reinforcements and a concomitant increase in 10-sec periods of non-responding (pause intervals). DOM was more potent when infused into the median raphe nucleus than following intracerebroventricular (ICV) administration. DOM was less potent when infused into the dorsal raphe, prefrontal cortex or dorsal hippocampus. Infusion of DOM into the lateral habenular nuclei produced a biphasic dose-response curve. ED50s for increases in pause intervals were 47, 77, 92, 103, and 114 micrograms for infusion into the median raphe, dorsal raphe, prefrontal cortex, lateral habenulae, and dorsal hippocampus, respectively. The ED50 for ICV administration in a previous study was 58 micrograms. The effects of DOM in the lateral habenulae could be divided into two curves; one curve had an ED50 of 69 micrograms, whereas the other had an ED50 of 176 micrograms. Furthermore, the dose-response curve for IP administration of DOM was shifted to the left in animals with cannulae placed into the lateral habenular nuclei. No change was seen in the response to IP administration of DOM in animals cannulated in the remaining sites or in animals with ICV cannulae. Therefore, the effects of DOM in disrupting operant behavior may be more critical with regard to its actions in the lateral habenulae and median raphe. Nonetheless, actions at multiple brain sites probably contribute to the total behavioral effects of the drug.