Direct binding of 3H-lisuride to adrenergic and serotonergic receptors

Concurrent measurement of serotonin metabolism and single neuron activity changes in the lateral hypothalamus of freely behaving rat

To further investigate the activity of serotonin neurons in relation to feeding behavior, the metabolic activity of the serotonergic system and single neuron activity changes in the lateral hypothalamic area (LHA) were investigated concurrently in freely behaving rats. The extracellular concentration of 5-hydroxyindoleacetic acid (5-HIAA), a metabolic product of serotonin in the LHA, began to increase concomitantly with the early stage of nocturnal eating. The increased 5-HIAA returned to the basal level within 3 or 4 h. In conjunction with the increase in serotonin metabolism, activity of 12 out of 30 LHA neurons (40%) increased, whereas it decreased in 7 (23%), and in 11 (37%) it showed no change. An intracerebroventricular injection of lisuride suppressed the increased activity in 7 of the 12 neurons, but had no effect on the others. These results suggest that the concurrent increase in serotonin metabolism and neuron activity changes in the LHA may occur in the early portion of the nocturnal eating period, and may be important in controlling feeding behavior.

The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous, intramuscular, and subcutaneous injection

The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 micrograms lisuride hydrogen maleate as an aqueous solution. After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml.min-1.kg-1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration. The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.

Inhibition of serotonergic dorsal raphe neurons by systemic and iontophoretic administration of buspirone, a non-benzodiazepine anxiolytic drug

Extracellular single-unit recordings were made from serotonergic dorsal raphe neurons in chloral hydrate anesthetized male Sprague-Dawley rats. Buspirone, a clinically effective non-benzodiazepine anxiolytic drug, caused inhibition of firing of these neurons when given by intravenous (ED50 = 0.011 mg/kg, i.v.), intraperitoneal (ED50 = 0.088 mg/kg, i.p.), and intragastric (effective dose = 1.0-20.0 mg/kg, i.g.) injection. Buspirone also inhibited these cells when it was administered to the outside of recorded neurons by microiontophoresis (effective currents = 2-15 nA). Iontophoretically applied buspirone did not potentiate nor block the effects of iontophoretically applied GABA. Systemic administration of two putative buspirone metabolites (1,2-pyrimidinyl piperazine and 5-hydroxy buspirone) in relatively high doses had a weak effect and no effect, respectively, on dorsal raphe neuronal firing. It is concluded that buspirone potently and directly inhibits the firing of serotonergic dorsal raphe neurons in the rat. Since buspirone inhibits the firing of serotonergic dorsal raphe neurons and binds to 5-HT1A receptors, the present study supports the notion that central serotonergic systems may be involved in the therapeutic effects of anxiolytic 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)