Studies on the specificity of neurochemical and behavioral effects of LSD-25

Abnormal behavioral responses to fenfluramine in patients with affective and personality disorders. Correlation with increased serotonergic responsivity

Serotonergic responsivity was assessed in 20 psychiatric patients by the prolactin response to a fenfluramine challenge test. During the fenfluramine challenge 6 of 20 patients (30%) spontaneously reported psychopathologic reactions that included: increased anxiety/agitation, psychotic symptoms, illusions, mood elevation, and anergia. The time of peak behavioral symptoms (2.5 +/- 0.8 hrs) corresponded closely to the time of peak increase in prolactin levels (3.0 +/- 1.1 hr). Abnormal behavioral responders had statistically significant greater increases in prolactin 1 to 4 hr after fenfluramine when compared to normal responders. Patients who developed an abnormal psychopathologic response to fenfluramine were characterized by higher levels of anxiety and agitation at the time of admission to the hospital but otherwise were not distinguishable on the basis of severity of other psychiatric symptoms. This study suggests that increased serotonergic transmission may trigger anxiety, psychosis, and mood elevation in specific vulnerable individuals, whereas other patients with similar psychiatric illnesses are not affected.

Behavioral, sleep-waking and EEG power spectral effects following the two specific 5-HT uptake inhibitors zimeldine and alaproclate in cats

Sleep, waking and EEG power spectra were studied in cats for 15 h following peroral administration of placebo or 10 mg/kg and 20 mg/kg of the 5-HT reuptake inhibitors zimeldine and alaproclate. Behavior was also observed during the initial period following drug administration. Both drugs had effects on motor behavior and initiated hallucinatory like behavior. Zimeldine increased latency to stable sleep and to SWS-2. Alaproclate increased latency to SWS-1. Both drugs increased SWS (NREM sleep) and particularly SWS-2. REM sleep latency was increased and REM sleep was reduced following both drugs. EEG slow wave activity was increased following zimeldine. It is concluded that the 5-HT stimulation caused by the drugs yields complex effects on the sleep-waking axis, both sleep incompatible and sleep promoting effects.

Evidence for antiserotonergic properties of yohimbine

Yohimbine (YOH) is a widely used pharmacological tool employed to produce a selective blockade of alpha 2-adrenergic receptors. In the present study operant behavior was used as a biobehavioral assay to determine the activity of YOH at serotonergic receptors, as indicated by its ability to antagonize the behavioral effects of a serotonergic agonist, lysergic acid diethylamide (LSD). Rats were trained to respond on a Fixed Ratio 15 schedule for food reinforcement. YOH (0.5-5.0 mg/kg) or vehicle and LSD (50 micrograms/kg) were administered (IP) 30 min and immediately prior, respectively, to the 30-min operant session. In a separate study, the ability of YOH (0.5-2.5 mg/kg) to antagonize a higher dose of LSD (100 micrograms/kg) was examined. Relatively low doses of YOH (0.5-1.0 mg/kg) were able to partially, but significantly antagonize the LSD-induced suppression and typical hallucinogen-induced disruption of schedule-controlled responding. These results suggest that YOH, even at moderate doses, may act nonselectively as an antagonist at 5-HT receptors, in addition to its antagonist action at alpha 2-adrenergic receptors. This study demonstrates the utility of operant behavior as a biobehavioral assay to study the receptor mediated action of drugs.

Comparative effects of LSD and lisuride: clues to specific hallucinogenic drug actions

This review compares the effects of LSD and its nonhallucinogenic congener lisuride hydrogen maleate (LHM) on various biochemical, behavioral and electrophysiological indices of neuronal function. The underlying rationale is that any differences between the effects of LSD and LHM might be relevant to neuronal actions which are unique and specific to hallucinogenic drugs and thereby provide clues to the neurobiological substrates of hallucinogenesis. In biochemical studies, LHM appears to be very similar to LSD with respect to its actions on monoaminergic (5-HT, DA, NE) systems. The major difference between the two ergots appears quantitative in nature since LHM is more potent than LSD, especially on DA neurochemistry. Needed at the present time are additional comparative studies of LSD and LHM with respect to other biochemical measures, for example on the release of 5-HT and DA and comparisons at more molecular levels such as subcellular compartmentation. Also necessary are more intensive regional analyses on specific subpopulations of 5-HT and DA systems (mesolimbic, mesostriatal and mesocortical). Behavioral studies are relatively uniform in their characterization of the greater DA-ergic activity of LHM as compared to LSD. In particular, the drug discrimination (DD) procedure has indicated a more specific interaction of LSD with 5-HT neuronal systems as compared to LHM and has successfully differentiated the relative roles of 5-HT and DA systems in the behavioral effects of LSD and LHM. Electrophysiological studies have been consistent with both biochemical and behavioral findings with respect to the much greater effect of LHM on DA receptors. In fact, the effects of LSD on DA-containing neurons are both weak and heterogeneous, again indicating a need for more detailed analyses of specific DA projection systems. The greater potency of LHM than LSD on 5-HT containing dorsal raphe neurons has lessened the attractiveness of the once popular theory that hallucinogenic efficacy is related to diminution of impulse flow in 5-HT systems but has also spawned greater interest in the possible role of postsynaptic 5-HT receptors in hallucinogenic drug action. Thus far, the most interesting finding is the ability of LSD and other hallucinogens, but not LHM, to potentiate an excitomodulatory effect of 5-HT in the facial motor nucleus. If such a phenomenon occurs more generally in the CNS, the importance of this finding will be greatly enhanced. Preliminary data is presented which suggests that LSD may also induce such an effect in a limbic forebrain structure, the nucleus accumbens.(ABSTRACT TRUNCATED AT 400 WORDS)