Effects of lisuride on body temperature of rats and rabbits: relation to microsomal biotransformation and dopaminergic receptor stimulation

Anticonvulsive effects of the dopamine agonist lisuride maleate after experimental traumatic brain injury

Traumatic brain injury is a heterogeneous disease, encompassing a wide range of pathologies. The dopamine agonist lisuride is well established in the therapy of Parkinson's disease. Additionally to its dopaminergic effects it decreases prolactine release, reducing the amount of inflammatory mediators such as TNF-alpha or Il-6. Lisuride has strong binding affinity to serotonergic and histaminergic receptors on neuronal and glial cells leading to scavenging of highly reactive free radicals. Due to its interaction with dopaminergic D2 and D4 receptors as well as 5-HT-1A receptors, NMDA-receptor signaling and glutamate-mediated excitotoxicity can be modulated beneficially. Despite of these promising neuroprotective effects, experimental data scrutinizing the effects of lisuride after acute brain injury are sparse. We therefore investigated the effect of lisuride after controlled cortical impact injury (CCII) in rats. 70 male Sprague-Dawley rats were randomized to lisuride or to placebo treatment by an initial s.c. loading dose (0.3mg/kg BW) and following continuous application (0.5mg/kg/d) by s.c. implanted osmotic pumps. In three experimental groups we determined (sub)acute neuro-physiological changes after trauma. Mean arterial blood pressure, intracranial pressure, and electrical brain activity were monitored acutely for up to 3h after trauma. Brain edema formation was assessed 24h after CCII. Furthermore, contusion volumes were quantified by magnetic resonance tomography and neurological testing was performed for up to 7 days after injury. Associated with the administration of lisuride there was a significant reduction in duration and number of post-traumatic seizures. Despite of a sustained arterial hypotension following the initial bolus administration in the treatment group, contusion volumes and neurological function tests did not differ significantly in comparison to the control group. Overall, lisuride seems to have significant anticonvulsive effects but seems not to influence secondary brain damage in this experimental model.

Tolerance to hypoactivity and sensitization to hyperactivity after chronic treatment with a presynaptic dose of lisuride in rats

We studied the adaptive changes of the locomotor effects of lisuride, a selective agonist for dopamine (DA) D2 receptors, and the functional state of D1 and D2 receptors after repeated administration of lisuride at a dose supposed to act preferentially on DA autoreceptors. Rats were treated daily with saline or lisuride, at a dose that causes a significant reduction in locomotor activity when given to naive rats (25 micrograms/kg i.p.), for 33 days and the effect of different challenging doses of the drug on locomotor activity was measured at different times during and after the treatment. The functional state of D1 and D2 DA receptors was evaluated by measuring SKF 82526-stimulated and LY 171555-inhibited adenylate cyclase (AC) activity in the caudatus/putamen, nucleus accumbens and substantia nigra and naive and chronically treated rats. There was a progressive decline in the ability of lisuride to decrease locomotor activity in rats given daily injections of lisuride, and there was a marked reduction in the threshold dose of lisuride for causing hypermotility. The functional state of DA receptors, positively or negatively linked to AC activity, was not modified by the treatment. The most suitable explanation of the reported adaptive behavioral changes is a down-regulation of DA autoreceptors after chronic treatment with presynaptic doses of lisuride.

The rise of body temperature induced by the stimulation of dopamine D1 receptors is increased in acutely reserpinized mice

In naive mice, the selective D1 agonist, SK&F 38393 (7.5-30 mg/kg s.c.), induced a significant rise of body temperature (0.5-1 degree C) which was antagonized by SCH 23390 (100 micrograms/kg s.c.) and by flupenthixol (0.4 mg/kg i.p.). In mice treated with reserpine (5 mg/kg s.c.) 18 h before testing, which on its own caused intense hypothermia (10-12 degrees C), SK&F 38393 (1.87-30 mg/kg s.c.) induced a dose-dependent and more marked rise of body temperature (5-7 degrees C). Similarly, SK&F 38393 (30 mg/kg s.c.) partially prevented reserpine-induced hypothermia. The central origin of the SK&F 38393 effects in reserpine-treated mice is indicated by the rise of body temperature induced by the i.c.v. administration of the drug (12.5-50 micrograms per mice). The SK&F 38393-induced rise of body temperature in acutely reserpinized mice was antagonized by SCH 23390 (50-200 micrograms/kg s.c.), clozapine (1.87-30 mg/kg i.p.) or chlorpromazine (2-32 mg/kg i.p.) but not by metoclopramide (25 or 100 mg/kg i.p.) or amisulpride (12.5 or 50 mg/kg). In naive mice, apomorphine (1 mg/kg s.c.) or LY 171555 (0.4 mg/kg s.c.) induced hypothermia which was antagonized by amisulpride (12.5 mg/kg i.p.); a transiently increased body temperature was even measured 30 min after apomorphine injection in amisulpride-treated mice. Apomorphine (1 mg/kg s.c.) induced a rise of body temperature in acutely reserpinized mice which was significantly reduced by SCH 23390 (50 and 200 micrograms/kg s.c.) and significantly increased by amisulpride (12.5 and 50 mg/kg i.p.). These data suggest that pharmacologically different dopamine receptor subtypes mediate different effects on body temperature in mice: D1 dopamine receptors mediate a rise of body temperature which is increased in hypothermic reserpinized animals and dopamine receptors of the D4 subtype mediate the decrease of body temperature in naive mice.

Repeated administration of lisuride down-regulates dopamine D-2 receptor function in mesostriatal and in mesolimbocortical rat brain regions

Functional modifications of both D-1 and D-2 dopamine (DA) receptor subtypes following repeated administration of lisuride, a DA agonist that acts selectively on D-2 DA receptors were studied. The functional state of D-1 and D-2 DA receptors was evaluated from measurements of SKF 82526-stimulated and bromocriptine-inhibited adenylate cyclase activity in different brain regions of rats treated daily for 26 days with saline or lisuride (100 micrograms/kg i.p.). Persistent stimulation by lisuride of DA receptors in striatum, nucleus accumbens, substantia nigra, frontal cortex, hippocampus and pituitary gland induced a down-regulation of D-2 receptors without changing the functional activity of D-1 receptors.

SCH 23390 antagonizes apomorphine- and ergot-induced hypothermia

The reportedly specific D-1 dopamine (DA) receptor antagonist SCH 23390 significantly reduced the hypothermia elicited by various DA receptor agonists like apomorphine, pergolide and lisuride. When tested against equihypothermic doses of each agonist, SCH 23390 significantly reduced the hypothermia elicited by apomorphine (0.2 mg/kg s.c.) and by pergolide (0.1 mg/kg i.p.) at doses of 0.025 mg/kg s.c. Doses of 0.050 mg/kg s.c. of SCH 23390 were necessary to reduce the hypothermia elicited by 0.012 mg/kg s.c. of lisuride. Pretreatment with the specific D-2 antagonist (-)sulpiride (50 mg/kg i.p.) completely prevented the hypothermia elicited by lisuride (0.012 mg/kg i.p.), pergolide (0.1 mg/kg i.p.) and apomorphine (0.2 mg/kg s.c.) and shifted to the right the dose-response curve for agonist-induced hypothermia. A study of the interaction between 0.05 mg/kg s.c. of SCH 23390 with various doses of the agonists showed that the effectiveness of SCH 23390 in antagonizing the hypothermia was maximal towards apomorphine and least towards lisuride for which significant antagonism was observed only against the lowest dose tested (0.012 mg/kg s.c.). The reportedly specific D-1 receptor agonist SKF 38393 given in doses up to 20 mg/kg i.p. or intracerebroventricularly up to 100 micrograms failed to influence body temperature while it evoked intense grooming and stimulated motility.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Tolerance to some behavioural effects of lisuride, a dopamine receptor agonist, and reverse tolerance to others, after repeated administration

To investigate whether prolonged pretreatment with the dopamine (DA) agonist lisuride would result in modification of some of its behavioural effects, food intake, locomotor activity, body temperature or stereotyped and mounting behaviour were evaluated after acute injections of different doses of lisuride into rats, pretreated daily for four weeks with either saline or lisuride. Rats pretreated with lisuride developed tolerance to its anorexigenic and hypothermic effects, and reverse tolerance to its effects on locomotor activity, stereotyped and mounting behaviour. Pretreatment with lisuride did not modify the activity of drug-metabolizing enzymes in the liver. These results, in addition to revealing the pattern of the changes in the behavioural effects of a DA agonist drug, after repeated administration, may be taken as evidence for the existence of different DA receptor systems in different areas of the brain, that mediate different behavioural effects, and that differ markedly in their reactions to prolonged stimulation with an agonist drug.

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents: II

This survey begins a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1978, but data from many earlier papers are also tabulated.

In vivo and in vitro dopaminergic effects of three ergoline fragments

The pharmacological effects of three ergoline fragments (BD-179, BD-271 and BD-214) were studied in vivo using the cat cardioaccelerator nerve preparation and in vitro using field stimulated isolated cat right atria. BD-179 and BD-271 produced dose dependent inhibition of tachycardia due to electrical stimulation of the right postganglionic cardioaccelerator nerve in anesthetized cats, BD-214 was inactive. BD-179 produced primarily hypotension, BD-271 produced a transient pressor response followed by hypotension and BD-214 produced only pressor effects. The tachycardia inhibitory effects and hypotension produced by BD-179 and BD-271 were antagonized by the dopamine receptor antagonist sulpiride. BD-179, BD-271 and BD-214 antagonized the presynaptic inhibitory effects of the dopamine receptor agonist apomorphine in vitro on field stimulated isolated cat right atria. All three ergoline fragments facilitated stimulation-induced increases in systolic tension development and BD-214 facilitated stimulation-induced tachycardia in isolated cat right atria.

Effects of GTP and sodium on rat striatal dopamine receptors labeled with lisuride

[3H]Lisuride binding to rat striatal membranes appeared to be stereospecifically displaced by the dopamine antagonist butaclamol. Sodium increased the number of [3H]lisuride binding sites (Bmax) without changing the dissociation constant (Kd). GTP did not affect [3H]lisuride binding characteristics, either with or without sodium. These results suggest that dopamine receptor sites labeled by lisuride are at least in part sodium-dependent, possibly the D2-receptors not involved in adenylate cyclase stimulation.

Effects of ibotenic acid-induced neuronal degeneration in the medial preoptic area and the lateral hypothalamic area on sexual behavior in the male rat

It is well known that electrolytic lesions in the medial preoptic area (MPOA) and the lateral hypothalamic area (LHA) seriously impair masculine sexual behavior in the rat. We here report that bilateral infusions of the neurotoxin, ibotenic acid (IBO), in the MPOA were as effective as electrolytic lesions in eliminating copulation whereas no behavioral effects were detected following similar infusions in the LHA. Histological examination of MPOA and LHA following IBO exposure revealed extensive degeneration of neuronal cell bodies with little evidence of non-specific damage. Also, immunohistochemical studies suggested that the serotonergic innervation of the MPOA remained largely intact in spite of IBO treatment; similarly, the damage inflicted by IBO in LHA on tyrosine hydroxylase-immunoreactive fibers in the medial forebrain bundle was insignificant. These data suggest that: (i) the functional integrity of MPOA nerve cell bodies is necessary for the expression of sexual behavior, and (ii) disruption of mating produced by electrolytic LHA lesions is due to disruption of medial forebrain bundle fiber systems. Behavioral observations of non-copulating males suggested that the MPOA injury did not interfere with all aspects of their sexual interaction with the estrous female; rather, they appeared specifically unable to perform the reflexive pelvic thrust pattern normally associated with mounting. We here report, however, that the ability to perform mounts with pelvic thrusts was temporarily restored in the vast majority of MPOA-injured males by the i.p. administration of the ergot derivative, lisuride. About 50% of these MPOA-damaged males even ejaculated, often after a low number of intromissions and short ejaculation latencies. On the other hand, injections of naloxone (an opiate receptor antagonist) failed to activate mounting in MPOA-lesioned or castrated rats. On the basis of these findings the possible ways in which steroid hormone-sensitive brain areas might interact with monoamine-containing pathways are discussed.U

Anorectic effect of lisuride and other ergot derivatives in the rat

Three ergot derivatives, lisuride, lergotrile and bromocriptine, given to rats trained to eat 4 h a day, induced a dose- and time-related anorexia. They were more potent in this context than either amphetamine or fenfluramine. Lisuride and lergotrile failed to increase locomotor activity or to induce stereotyped behaviour at doses corresponding to the ID50 on food intake. At this dose, bromocriptine slightly stimulated motor activity. The anorectic effect of the three compounds was selectively antagonized by blockers of dopamine (DA) receptors in the central nervous system but not by either inhibiton of catecholamine synthesis or blockade of alpha- or beta-adrenoceptors or of serotonergic receptors. Also two blockers of 'peripheral' DA receptors failed to antagonize ergoline-induced anorexia. These findings indicate that stimulation of DA receptors involved in feeding behaviour was responsible for the anorexigenic effect of the ergot derivatives investigated. In most instances this effect occurred at dose levels which failed to induce central stimulant effects.