Effect of cholingeric drugs on methadone-induced catalepsy and stereotypies in rats treated chronically with methadone

Selective interaction of homophtalazine derivatives with morphine

Homophtalazines show specific binding sites in the nigrostriatal system and to find their target of action the interactions between these derivatives, nerisopam and girisopam, and chlorpromazine, chlordiazepoxide and morphine were assessed. The compounds did not influence the chlorpromazine induced decrease in motility and catalepsy, nor did they alter the antiaggressive and anticonvulsive action of chlordiazepoxide. However, nerisopam and girisopam augmented the agonist potency of morphine to induce catalepsy or analgesia; they also altered the opioid antagonist potency of naloxone. The naloxone-induced decrease in sucrose consumption in drinking water was augmented by nerisopam and girisopam. It is suggested that a possible target of action of homophtalazines is the opioid signal transduction.

Neuroleptic-induced catalepsy as a model of Parkinson's disease. II. Effect of glutamate antagonists

Subcutaneous administration of fluphenazine elicits catelepsy that can be attenuated by the glutamate antagonists MK801 and phencyclidine (PCP). 3-[-(+)-2-carboxy piperazine-4-yl]-propyl-1-phosphanate (CPP) was found to be ineffective in this model. Intrastriatal injections of sulpiride or fluphenazine were also found to induce catalepsy which could be attenuated by MK801 and PCP. These results illustrate that nondopaminergic compounds might possibly be of value in the treatment of Parkinson's disease. Furthermore it was demonstrated that this paradigm can be utilized to investigate neurotransmitter interactions within the striatum. This was clearly emphasized by the observation that bilateral administration of MK801 into the striatum increased basal locomotor activity.

Enhancement of opioid cataleptic response by cortical frontal deafferentation or intrastriatal injection of NMDA-receptor antagonists

The cataleptic activity of morphine and methadone was markedly potentiated in frontally decorticated rats with no apparent changes in the onset or duration of action. Enhancement of the opioid cataleptic response was not due to changes in the availability of the drugs in the brain. The potentiation of methadone-induced catalepsy in decorticated rats was mimicked in naive rats by intrastriatal (i.s.) application of 2-amino-7-phosphonoheptanoic acid (AP7), a potent and selective antagonist of N-methyl-D-aspartate (NMDA) receptors. Therefore, degeneration of glutamatergic synapses following decortication could be responsible for the changes in behavioral effects caused by opioids. The failure of AP7 to elicit an effect after injection into the n. accumbens fits with the possibility of a selective involvement of the striatum in this phenomenon. That the striatum plays a critical role in the expression of opioid-induced catalepsy was substantiated by the findings that: (1) naloxone, an opioid antagonist, injected i.s., prevents the potentiation of catalepsy induced by methadone and morphine in decorticated animals, (2) oxotremorine, a muscarinic agonist, injected i.s., reverses the enhancement of opioid-catalepsy in decorticated rats, (3) earlier studies by others showed that ablation of the striatum had a facilitatory action on opioid-induced catalepsy. In conclusion, evidence is given that the corticostriatal pathway exerts an inhibitory effect upon narcotic-induced cataleptic behavior. The possibility that this effect is mediated through striatonigral GABAergic output is discussed. The data further suggest that the neuronal mechanisms through which the corticostriatal pathway mediates narcotic catalepsy is operative through activation of NMDA receptors within the striatum.

Delirium and stereotypy from anticholinergic antiparkinson drugs

1. This report describes two cases of psychotic syndrome from benztropine (Cogentin), which was used to treat haloperidol-induced extrapyramidal side effects. The patients' symptomatology meets DSM III criteria for delirium. Both patients displayed repetitive motor automatisms (stereotypy). 2. Symptomatology appeared one-to-two days after the start of benztropine 2 mg b.i.d. and subsided one-to-several days after benztropine was stopped. Treatment consisted of administration of sedative hypnotic drugs. 3. The literature on anticholinergic-induced psychotic syndromes is surveyed. Particular attention is drawn to the occurrence of stereotypy. 4. It is proposed, on the basis of a review of animal and clinical data, that stereotypies in delirious patients are related to muscarinic blockade in the central nervous system. This model is used to explain repetitive motor automatisms which are seen in Alzheimer's disease. 5. The paper concludes with brief guidelines for the management of anticholinergic delirium.

Effect of nicotinic and muscarinic drugs on amphetamine- and apomorphine-induced circling behaviour in rats

The effect of drugs modulating the activity of nicotinic or muscarinic cholinergic receptors on the circling behaviour induced by amphetamine and apomorphine in rats with unilateral 6-hydroxydopamine lesion of nigrostriatal dopaminergic pathway was studied. Nicotine (0.2 mg/kg subcutaneously) significantly increased amphetamine-induced circling behaviour and tended to inhibit apomorphine-induced circling behaviour. Mecamylamine and pempidine (both 2 mg/kg intraperitoneally) slightly but significantly depressed the intensity of circling behaviour induced by amphetamine, but failed to modify the induced by apomorphine. Pilocarpine (10 mg/kg intraperitoneally) clearly inhibited both amphetamine- and apomorphine-induced circling behaviour. Unlike pilocarpine, atropine (10 mg/kg intraperitoneally significantly increases the intensity of the circling behaviour induced by amphetamine and also to some extent that induced by apomorphine. Neither hexamethonium (5 mg/kg intraperitoneally) nor methylatropine (1 mg/kg subcutaneously) modified the circling behaviour induced by either amphetamine or apomorphine. The results show that stimulation of central nicotinic and muscarinic receptors may have some opposite effects on the dopamine dependent circling behaviour. The presynaptic nicotinic cholinergic receptors on the terminals of the nigrostriatal dopaminergic neurones, stimulation of which may increase the release of dopamine, might be involved in the action of nicotinic drugs. The muscarinic cholinergic receptors in the striatum and/or in the substantia nigra might be involved in the action of muscarinic drugs.

Effects of dopaminergic and cholinergic drugs. naloxone and l-prolyl-leucyl-glycinamide on LSD-induced catalepsy

In an attempt to elucidate the mechanism of d-lysergic acid diethylamide (LSD) induced catalepsy, the effects of cholinergic and dopaminergic agents, naloxone and L-propyl-leucyl-glycinamide (PLG) were studied in rats. The dose-dependent (50--500 micrograms kg-1 s.c.) and time-related cataleptic response elicited by LSD was preceded by a phase of hyperexcitability. The non-hallucinogenic analogue, 2-bromo-LSD (BOL), was without effect. Both apomorphine, the dopamine agonist, and L-DOPA antagonized LSD-induced catalepsy whereas the dopamine depleting agent alpha-methyl-p-tyrosine (alpha-MPT) slightly prolonged the cataleptic effect. Cholinergic muscarinic receptor stimulation with pilocarpine antagonized LSD-induced catalepsy. The muscarinic antagonists, atropine and scopolamine, intensified the hyperexcitable phase and potentiated the cataleptic effects of LSD. Nicotine slightly potentiated LSD action but mecamylamine antagonized it. While pre-treatment with naloxone, the narcotic antagonist and PLG prolonged the cataleptic response, post-treatment with naloxone effectively attenuated LSD-induced catalepsy. The behavioural data are interpreted to suggest that LSD-induced catalepsy may be mediated through diminished dopaminergic and cholinergic neuronal activity and under enkephalinergic modulation. The neuroanatomical foci and exact mechanism of action remain to be delineated.

The influence of 5-HT receptor blocking agents on the behavioral effects of analgesics in rats

The influence of methergoline, methysergide, mianserine, cyproheptadine, and pizotifen on catalepsy induced by morphine, codeine, and fentanyl, and antinociception induced by these three drugs and by pentazocine was studied in rats. Methergoline dose-dependently reduced catalepsy induced by these three drugs. Methysergide abolished only morphine catalepsy, while mianserine significantly reduced the effect of morphine and codeine. Cyprohepatide and pizotifen did not modify the cataleptic effect of the three analgesics used. Antinociceptive action of morphine, codeine, fentanyl, and pentazocine, measured by the hot plate method, was not influenced or changed differentially by any serotonin receptor blocking compounds. One may conclude that catalepsy induced by morphine is, in general, antagonized by serotonin receptor blockade, but this does not concern all narcotic analgesics. In the antinociceptive effects of drugs used, the serotonergic influence seems to play a less important role than in catalepsy.

The influence of cerebral 5-hydroxytryptamine on catalepsy induced by brain-amine depleting neuroleptics or by cholinomimetics

1 Catalepsy was produced in rats and mice by the subcutaneous injection of either tetrabenazine or the butyrophenone U-32,802A (4'-fluoro-4-{[4-(p-fluorophenyl)-3-cyclohexen-1-yl]amino} butyrophenone hydrochloride). Catalepsy was evaluated by the duration of total immobility on a vertical grid.2 Pretreatment with p-chlorophenylalanine (PCPA) reduced the intensity of catalepsy by 50% or more, whereas its time course remained the same.3 5-Hydroxytryptophan (5-HTP), 10 mg/kg, enhanced the catalepsy induced by U-32,802A or tetrabenazine, provided it was administered soon (45 min) after the neuroleptic; injections at 90 min had no effect. Otherwise untreated rats given this dose of 5-HTP behaved normally on the grid.4 The anticataleptic effect of PCPA was reversed by 5-HTP.5 Measurable changes in 5-hydroxytryptamine (5-HT) metabolism in the rat forebrain accompanied the modification of catalepsy by 5-HTP and PCPA.6 Methysergide (5 mg/kg) given 30 min before the neuroleptics to either mice or rats reduced the catalepsy, assessed 2.5 h after the methysergide. It also prevented the increase in neuroleptic-induced catalepsy following 5-HTP, 10 mg/kg.7 Tryptophan, like 5-HTP, increased the catalepsy seen in mice after U-32,802A and tetrabenazine, and increased the production of 5-hydroxyindol-3-ylacetic acid in the forebrain.8 In the rat, intracerebroventricular injection of physostigmine produced catalepsy which was not modified by methysergide or PCPA but was abolished by atropine. Similarly, in the mouse, catalepsy induced by the subcutaneous injection of pilocarpine was abolished by atropine but not affected by either methysergide or 5-HTP.9 Atropine greatly reduced the catalepsy induced by U-32,802A and tetrabenazine but lowered striatal homovanillic acid (HVA) only after U-32,802A. D,L-DOPA, 20 mg/kg, diminished the cataleptogenic effect of both neuroleptics and raised striatal HVA.10 The results support the view that there is a facilitating or permissive action of 5-HT-containing neurones on neuroleptic-induced catalepsy.

Antagonism of morphine-induced catalepsy by L-prolyl-L-leucyl-glycinamide

In view of the recently demonstrated extra-endocrine central actions of hypothalamic releasing hormones, we have investigated the effects of prolyl-leucyl-glycinamide (PLG) and thyrotropin releasing hormone (TRH) on morphine-induced catalepsy. Although acute administration of PLG (10 mg kg-1 s.c.) slightly attenuated the cataleptic response, chronic PLG treatment (10 mg kg-1 s.c. for 10 days) virtually abolished morphine-induced catalepsy. TRH, administered subcutaneously, exhibited little or no anti-cataleptic activity. These results are discussed in relation to the possible central site of narcotic-induced catalepsy and the therapeutic potential of PLG in Parkinson's disease.

Effect of mecamylamine on the fate of dopamine in striatal and mesolimbic areas of rat brain; interaction with morphine and haloperidol

1 The effects of the nicotinic cholinoceptor blocking drug, mecamylamine (alone or in combination with morphine or haloperidol) were investigated on the striatal homovanillic acid (HVA) concentration and on the alpha-methyl-p-tyrosine (AMPT)-induced depletion of striatal or mesolimbic dopamine content in the brain of rats. 2 Mecamylamine (2 mg/kg) alone did not alter the striatal HVA concentration, but it reduced the probenecid-induced accumulation of HVA. Mecamylamine pretreatment reduced the morphine- and haloperidol-induced elevation of striatal HVA concentrations. Hexamethonium did not alter the striatal HVA concentration when given alone or in probenecid- or morphine-treated rats, whereas pempidine (8 mg/kg) clearly reduced the probenecid-induced accumulation of HVA in the striatum. 3 Mecamylamine (2 and 8 mg/kg) slowed the rate of AMPT-induced depletion of dopamine from the striatum and mesolimbic area both in the brain of control rats treated with morphine or haloperidol. 4 Mecamylamine slightly prolonged the cataleptic effect of morphine. 5 The results indicate that mecamylamine inhibits the release of dopamine both from the striatal and mesolimbic dopaminergic neurones.

beta-Endorphin: endogenous opiate or neuroleptic?

The opiatelike neuropeptide beta-endorphin produces a spectrum of effects that contrasts with that induced by the neuroleptic haloperidol. Rats injected intraventricularly or directly into the periaqueductal gray with beta-endorphin (0.5 to 50 micrograms) exhibited rigid immobility accompanied by the loss of righting reflex; the period of rigidity was preceded or followed (depending upon dose) by a state of hyperactivity. In contrast, no dose of haloperidol tested (0.5 to 12 milligrams per kilogram) produced rigidity, loss of righting reflex, or behavioral excitation. Furthermore, whereas animals injected with haloperidol remained stationary on a vertical grid, rats injected with beta-endorphin typically slid off the grid. Moreover, combined beta-endorphin and haloperidol treatment produced flaccidity in most animals. These results do not support the contention that this opiatelike peptide may be a naturally occurring neuroleptic.

Effect of muscarinic cholinergic drugs on morphine-induced catalepsy, antinociception and changes in brain dopamine metabolism

The effects of drugs acting on muscarinic cholinergic receptors on the catalepsy, antinociception and changes in rectal temperature and in brain dopamine metabolism induced by morphine were studied in Wistar rats. Scopolamine (0.3 - 30 mg/kg) was about three times as potent as atropine (1 - 30 mg/kg) in potentiating the cataleptic effect of morphine. Methylscopolamine and methylatropine did not alter the cataleptic effect of morphine. Pilocarpine (100 mg/kg) and arecoline (10 mg/kg) slightly but significantly and RS86 (20 - 40 mg/kg) clearly antagonized the morphine-catalepsy. RS86 antagonized the atropine-induced potentiation of morphine catalepsy. The antinociceptive effect of pilocarpine was additive and that of RS86 less than additive with morphine. The antimuscarinic compounds did not alter the antinociceptive effect of morphine. Antimuscarinic compounds enhanced the hypothermic effect of morphine, but none of the compounds studied altered the hyperthermic effect of morphine. The antimuscarinic drugs reduced the concentration of striatal homovanillic acid (HVA) in about same proportion in control and morphine-treated rats. Both the muscarinic compounds and morphine increased the concentration of striatal HVA, but when combined their effects were not significantly different from those of morphine alone. Scopolamine antagonized and pilocarpine accelerated the morphine-induced increase in the rate of depletion of cerebral dopamine content. The present results show that the effects of muscarinic aand antimuscarinic cholinergic drugs on the cataleptic effect of morphine were opposite to their effects on the catalepsy induced by neuroleptic compounds.