Dopaminergic alterations in cotreatments attenuating haloperidol-induced hypersensitivity

Asenapine sensitization from adolescence to adulthood and its potential molecular basis

Asenapine is a new antipsychotic drug that induces a long-lasting behavioral sensitization in adult rats. The present study investigated the developmental impacts of adolescent asenapine treatment on drug sensitivity and on 3 proteins implicated in the action of antipsychotic drugs (i.e. brain-derived neurotrophic factor (BDNF), dopamine D2 receptor, and ΔFosB) in adulthood. Male adolescent Sprague-Dawley rats (postnatal days, P 43-48) were first treated with asenapine (0.05, 0.10 or 0.20mg/kg, sc) and tested in the conditioned avoidance or PCP (2.0mg/kg, sc)-induced hyperlocomotion tasks for 5 days. After they became adults (∼P 76), asenapine sensitization was assessed in a single avoidance or PCP-induced hyperlocomotion challenge test with all rats being injected with asenapine (0.10mg/kg, sc). Rats were then sacrificed 1 day later and BDNF, D2 and ΔFosB in the prefrontal cortex, striatum and hippocampus were examined using Western blotting. In adolescence, repeated asenapine treatment produced a persistent and dose-dependent inhibition of avoidance response, spontaneous motor activity and PCP-induced hyperlocomotion. In the asenapine challenge test, adult rats treated with asenapine (0.10 and 0.20mg/kg) in adolescence made significantly fewer avoidance responses and showed a stronger inhibition of spontaneous motor activity than those previously treated with saline. However, no group difference in the levels of BDNF, D2 and ΔFosB expression was found. These findings suggest that although adolescent asenapine treatment for a short period of time induces a robust behavioral sensitization that persists into adulthood, such a long-term effect is not likely to be mediated by BDNF, D2 and ΔFosB.

Adult response to olanzapine or clozapine treatment is altered by adolescent antipsychotic exposure: a preclinical test in the phencyclidine hyperlocomotion model

This study examined how repeated olanzapine (OLZ) or clozapine (CLZ) treatment in adolescence alters sensitivity to the same drug in adulthood in the phencyclidine (PCP) hyperlocomotion model. Male adolescent Sprague-Dawley rats (postnatal day (P) 44-48) were first treated with OLZ (1.0 or 2.0 mg/kg, subcutaneously (sc)) or CLZ (10.0 or 20.0 mg/kg, sc) and tested in the PCP (3.2 mg/kg, sc)-induced hyperlocomotion model for five consecutive days. Then a challenge test with OLZ (0.5 mg/kg) or CLZ (5.0 mg/kg) was administered either during adolescence (~P 51) or after the rats matured into adults (~P 76 and 91). During adolescence, repeated OLZ or CLZ treatment produced a persistent inhibition of PCP-induced hyperlocomotion across the five test days. In the challenge test during adolescence, rats previously treated with OLZ did not show a significantly stronger inhibition of PCP-induced hyperlocomotion than those previously treated with vehicle (VEH). In contrast, those previously treated with CLZ showed a weaker inhibition than the VEH controls. When assessed in adulthood, the enhanced sensitivity to OLZ and the decreased sensitivity to CLZ were detected on ~P 76, even on ~P 91 in the case of OLZ. These findings suggest that adolescent OLZ or CLZ exposure can induce long-term alterations in antipsychotic response that persist into adulthood.

6-Hydroxydopamine-induced alterations in blood-brain barrier permeability

Vascular inflammation is well known for its ability to compromise the function of the blood--brain barrier (BBB). Whether inflammation on the parenchymal side of the barrier, such as that associated with Parkinson's-like dopamine (DA) neuron lesions, similarly disrupts BBB function, is unknown. We assessed BBB integrity by examining the leakage of FITC-labeled albumin or horseradish peroxidase from the vasculature into parenchyma in animals exposed to the DA neurotoxin 6-hydroxydopamine (6OHDA). Unilateral injections of 6OHDA into the striatum or the medial forebrain bundle produced increased leakage in the ipsilateral substantia nigra and striatum 10 and 34 days following 6OHDA. Microglia were markedly activated and DA neurons were reduced by the lesions. The areas of BBB leakage were associated with increased expression of P-glycoprotein and beta 3-integrin expression suggesting, respectively, a compensatory response to inflammation and possible angiogenesis. Behavioural studies revealed that domperidone, a DA antagonist that normally does not cross the BBB, attenuated apomorphine-induced stereotypic behaviour in animals with 6OHDA lesions. This suggests that drugs which normally have no effect in brain can enter following Parkinson-like lesions. These data suggest that the events associated with DA neuron loss compromise BBB function.

Chronic lithium chloride administration to unanesthetized rats attenuates brain dopamine D2-like receptor-initiated signaling via arachidonic acid

We studied the effect of lithium chloride on dopaminergic neurotransmission via D2-like receptors coupled to phospholipase A2 (PLA2). In unanesthetized rats injected i.v. with radiolabeled arachidonic acid (AA, 20:4 n-6), regional PLA2 activation was imaged by measuring regional incorporation coefficients k* of AA (brain radioactivity divided by integrated plasma radioactivity) using quantitative autoradiography, following administration of the D2-like receptor agonist, quinpirole. In rats fed a control diet, quinpirole at 1 mg/kg i.v. increased k* for AA significantly in 17 regions with high densities of D2-like receptors, of 61 regions examined. Increases in k* were found in the prefrontal cortex, frontal cortex, accumbens nucleus, caudate-putamen, substantia nigra, and ventral tegmental area. Quinpirole, 0.25 mg/kg i.v. enhanced k* significantly only in the caudate-putamen. In rats fed LiCl for 6 weeks to produce a therapeutically relevant brain lithium concentration, neither 0.25 mg/kg nor 1 mg/kg quinpirole increased k* significantly in any region. Orofacial movements following quinpirole were modified but not abolished by LiCl feeding. The results suggest that downregulation by lithium of D2-like receptor signaling involving PLA2 and AA may contribute to lithium's therapeutic efficacy in bipolar disorder.

Does nicotine affect D2 receptor upregulation? A case-control study

OBJECTIVE

Nicotine has a powerful preventive effect on neuroleptic-induced dopamine D2 receptor upregulation in the rat. The aim of this human positron emission tomography (PET) study was to compare upregulation in a smoker and a non-smoker, both of whom had received haloperidol for the same duration of time.

METHOD

Two subjects who had been treated for 16 years with a constant dose of haloperidol were scanned after temporary haloperidol withdrawal, using [11C]-raclopride.

RESULTS

The non-smoker, who had received a dose of 10 mg/day, showed a D2 upregulation of 98% and developed severe and persistent symptoms of tardive dyskinesia (TD) upon withdrawal. The chronic smoker, who had been treated with 40 mg/day, displayed a D2 upregulation of 71% and did not develop TD.

CONCLUSION

These human observations agree with animal data which showed that nicotine can decrease neuroleptic-induced D2 receptor upregulation. This property of nicotine may play a protective role in movement disorders whose pathophysiology involves D2 receptor hypersensitivity.

Effects of lithium carbonate on apomorphine-induced sniffing behaviour in rats

Effects of lithium carbonate (Li2CO3) on sniffing induced by apomorphine have been tested in rats. Intraperitoneal administration of different doses of apomorphine (0.25, 0.5 and 1 mg/kg) induced a dose-dependent sniffing response. Chronic Li2CO3 exposure (0.1% in drinking water for 30-35 days) but not acute administration of the drug (320 mg/kg, intraperitoneally) decreased the response of apomorphine. The response to chronic Li2CO3 exposure was observed when apomorphine was injected 60 min., 24 hr or 72 hr after Li2CO3withdrawal, with maximum effect observed when the drug was administered 72 hr after withdrawal of Li2CO3. Blockade of sniffing induced by apomorphine by the D1 dopamine receptor antagonist, SCH23390 (0.005 mg/kg, intraperitoneally) or the D2 dopamine receptor antagonist, sulpiride (25 mg/kg, intraperitoneally) was not increased in acute Li2CO3-treated animals. In animals which were treated chronically with Li2CO3, the blockade of apomorphine response by sulpiride but not by SCH23390 was potentiated. It is concluded that chronic treatment of animals with Li2CO3 is able to alter D2 dopamine receptors response.

Effects of lithium, alone or associated with pilocarpine, on muscarinic and dopaminergic receptors and on phosphoinositide metabolism in rat hippocampus and striatum

The mechanism of action of lithium (Li) alone or with pilocarpine (Pilo), focusing on muscarinic and dopaminergic systems and also on phosphoinositide metabolism was studied. Li (3 mEq/kg) administered to rats once (1 d) or daily for 7 days (7 d), 24 h before Pilo (15 mg/kg), exacerbated cholinergic signs, leading to tremors. convulsions and brain lesions. Increases in muscarinic receptors (MR) of 29 and 49% were observed in the hippocampus after atropine (Atro) and Li-Atro-Pilo treatments, respectively, as compared to controls (Atro) and the Li-Pilo group (Li-Atro-Pilo). In the striatum, except for the 37% increase in the Li-Atro (50 mg/kg)-Pilo group as compared to the Li-Pilo one, no other changes were observed in MR. A decrease of 32% on average in D2-like receptors (D2R) was detected in the hippocampus in the group Li-7d. On the contrary, in the striatum an increase (25%) in the Li-7d group was observed and this effect was blocked by Li-Pilo. As far as inositol phosphates (IP) and phosphatidylinositol-4,5-biphosphate (PIP2) metabolism is concerned, Li caused a decrease (28%) and an increase (60%) in IP and PIP2 accumulations, respectively, in hippocampus slices while Pilo only altered IP accumulation (32% decrease). In this area the association of Li-Atro (10 mg/kg)-Pilo also caused a decrease (36%) in PIP2 as compared to the Li-Pilo group. In striatal slices, except for the Li, Atro (10 mg/kg) and Li-Atro (10 mg/kg)-Pilo groups which showed a decrease (33 40%) in IP accumulation, no other alteration was detected. The potentiation of the effect of Pilo by Li does not seem to depend on the PI metabolism, but instead on its involvement with muscarinic and dopaminergic systems.

The effect of acute lithium and rubidium pretreatment on apomorphine-induced pecking in pigeons

The effects of different doses of lithium (5-320 mg/kg intramuscularly) and rubidium (0.25 32 mg/kg intramuscularly) on apomorphine-induced pecking were investigated in pigeons. These two cations did not induce pecking by itself. Intramuscular administration of apomorphine (a mixed D1/D2 dopamine receptors agonist, 0.1-1.6 mg/kg) induced pecking in a dose-dependent manner. SCH 23390 (D1 dopamine receptor antagonist, 0.02-0.08 mg/kg) and sulpiride (D2 dopamine receptor antagonist, 25-100 mg/kg) decreased apomorphine-induced pecking dose-dependently. Combination of SCH 23390 (0.04 mg/kg) with sulpiride (50 mg/kg) caused a stronger inhibitory effect on apomorphine response. This indicates that both D1 and D2 dopamine receptors are involved in apomorphine-induced pecking. The response induced by apomorphine (0.2-0.8 mg/kg) was decreased in animals pretreated with lithium and rubidium. In these conditions, SCH 23390 and sulpiride produced a larger inhibitory effect on the apomorphine response, suggesting that acute lithium and rubidium pretreatment inhibit pecking by interfering with dopaminergic mechanisms.

Effects of buspirone on dopaminergic supersensitivity

The effects of buspirone treatment on dopaminergic supersensitivity induced by long-term haloperidol administration were studied; both spontaneous activity (locomotion and rearing frequencies) of rats observed in an open-field and apomorphine-induced stereotypy were used as experimental parameters. Buspirone per se (3.0 mg/kg, twice daily, for 30 days) did not produce dopaminergic supersensitivity. When buspirone was given in combination to haloperidol (2.0 mg/kg, once daily, for 30 days), it decreased the neuroleptic withdrawal symptoms as detected in open-field behavior but not in apomorphine-induced stereotypy. Although single administration of buspirone per se decreased both open-field and apomorphine-induced stereotypy behavior, buspirone single administration did not modify the acute effects of haloperidol on these two behavioral models. Taken together with previous behavioral results showing that buspirone reverses haloperidol-induced catalepsy, the present data suggest that buspirone co-administration may lead to important clinical advantages concerning different extrapyramidal side effects of neuroleptic treatment.

Effect of long-term haloperidol treatment on striatal neuropeptides: relation to stereotyped behavior

Behavioral and biochemical responses to D1 and D2 dopamine (DA) agonists were used to evaluate the participation of striatal peptidergic mechanisms in the motor function alterations that attend chronic neuroleptic treatment. Rats, given haloperidol (1 mg/kg, i.c.) for 21 consecutive days, were randomly allocated to one of the following treatments: the D1 agonist SKF 38393, the D2 agonist quinpirole, their combination or saline. Stereotyped behavior and neuropeptide levels were evaluated after 5 days treatment and 4 days washout. Haloperidol increased most oral behaviors including licking, chewing and biting as well as striatal enkephalin and somatostatin levels. Subsequent treatment with SKF 38393 diminished the haloperidol-induced increase in licking and chewing; quinpirole reduced chewing behavior. The administration of both agonists together decreased chewing and biting. Neither DA agonist alone, nor their combination, reduced the haloperidol-induced increase in enkephalin levels. Both SKF 38393 and quinpirole, when given alone, tended to decrease the haloperidol-induced increase in somatostatin levels; when both D1 and D2 agonists were administered together, somatostatin levels declined significantly. These results suggest that somatostatin- but not enkephalin-containing striatal neurons contribute to the expression of haloperidol-induced stereotypies.

Prenatal cocaine exposure and postnatal hypoxia independently decrease carotid body dopamine in neonatal rats

The effects of prenatal cocaine exposure on the levels of carotid body dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were investigated in 5-day-old rat pups exposed to normoxic and hypoxic conditions. Timed-pregnant Sprague-Dawley rats were injected b.i.d. with either cocaine HCl (30 mg/kg) or isotonic saline (1 ml/kg) from gestational days 7-21. On the fifth postnatal day, pups were subjected to either 20 min of 0.21 or 0.08 fractional inspired oxygen (FlO2). Under a strictly timed protocol, both carotid bodies were removed from each pup, placed in an antioxidant solution to prevent DA breakdown, and subsequently analyzed via HPLC with electrochemical detection to determine carotid body DA and DOPAC content. Two-way ANOVA revealed decreases in DA in cocaine-exposed pups. No HVA was detectable in any of the samples. The 0.08 FlO2 condition decreased DA compared to 0.21 FlO2. The additive consequences of DA depletion resulting from the combination of prenatal cocaine and postnatal hypoxia decreased carotid body DA to 14% of control levels, with several animals exhibiting DA content below detection limits. Considering the role of the carotid body in the ventilatory response to hypoxia, these data suggest that prenatal cocaine exposure may adversely affect the normal chemoreceptive function of the carotid body.

Effects of chronic lithium pretreatment on apomorphine-induced penile erection

1. The effects of chronic lithium pretreatment (600 mg/l in drinking rats, 30 days) on penile erection (PE) induced by apomorphine were investigated in rats. This treatment resulted in a serum Li concentration after 30 days of 0.31 +/- 0.01 mmol/l. 2. Subcutaneous (s.c.) administration of mixed D1/D2 dopamine receptor agonist apomorphine (0.05-0.5 mg/kg) induced PE in a biphasic manner. The maximum effect was obtained with 0.1 mg/kg of the drug while the response decreased with increasing doses of apomorphine from 0.1 to 0.5 mg/kg. 3. Pretreatment of animals with 0.0125-0.1 mg/kg of D1 dopamine receptor antagonist SCH 23390 or D2 dopamine receptor antagonist sulpiride (12.5-100 mg/kg) decreased apomorphine-induced PE. Combination of SCH 23390 (0.025 mg/ kg) with sulpiride (12.5 mg/kg) caused a stronger inhibitory effect on apomorphine response. This indicates that both D1 and D2 dopamine receptors may be involved in PE induced by apomorphine. 4. The response induced by apomorphine (0.05-0.05 mg/kg) was decreased in animals pretreated with chronic lithium. The inhibitory effect of sulpiride on apomorphine response, increased in animals pretreated with lithium, in contrast the inhibitory effect of SCH 23390 did not change in this condition. However, a combination of SCH 23390 with sulpiride increased inhibitory effect on apomorphine response in lithium pretreated rats. 5. It is concluded that chronic lithium inhibits PE induced by dopaminergic mechanism(s).

Alterations in striatal neurotrophic activity induced by dopaminergic drugs

The administration of dopaminergic drugs induces a variety of compensatory responses ostensibly designed to reinstate normal dopamine (DA) tone. We have hypothesized that drug-induced alterations in striatal-derived neurotrophic activity contributes to these compensatory processes. This phenomenon has been studied by examining the growth of mesencephalic cultures incubated with cell-free extracts of striatal tissue taken from patients or rats treated with various drugs. Our results reveal that reducing striatal DA tone by administering the DA antagonist haloperidol, the DA neurotoxin 6-hydroxydopamine, or as occurs naturally in Parkinson's disease, increases striatal trophic activity. Conversely, increasing striatal DA tone by administering the indirect DA agonists amphetamine or levodopa reduces trophic activity in the striatum. Kainic acid lesions of the striatum similarly reduce this trophic activity. The implications of these drug-induced alterations in trophic activity are discussed and reviewed.

Dopamine D1 receptor stimulation but not dopamine D2 receptor stimulation attenuates haloperidol-induced behavioral supersensitivity and receptor up-regulation

The effect of selective dopamine D1 and D2 receptor agonists on chronic haloperidol-treated rats was studied. Haloperidol treatment produced a 77% increase in apomorphine-induced sterotypy. The administration of the selective dopamine D1 receptor agonist SKF38393 alone or in combination with the selective dopamine D2 receptor agonist quinpirole attenuated the effect of haloperidol. Treatment with quinpirole alone did not have a significant effect on the response to haloperidol. Haloperidol did not modify the number of dopamine D1 receptors but increased that of dopamine D2 receptors. SKF38393 reversed the effect of haloperidol on dopamine D2 receptor binding. Co-administration of SKF38393 and quinpirole did not modify the increase in the number of dopamine D2 receptors induced by chronic treatment haloperidol. The results confirm a dissociation between behavioral supersensitivity and dopamine receptor up-regulation, suggesting that other mechanisms may be involved in the expression of behavioral supersensitivity.

Sensitization to haloperidol-induced suppression of milk intake: effect of interdose interval

The purpose of this study was to determine the effect of manipulating the interdose interval (IDI) on the suppression of milk intake induced by haloperidol (HAL). Groups of rats were given chronic injections of either HAL (0.625 mg/kg) or saline at IDIs of 1, 2, 7, or 14 days. Dose-response curves were determined at the conclusion of the chronic phase. The results indicated that injections of HAL given at IDIs of 1 or 2 days produced neither tolerance nor sensitization, whereas injections given at intervals of 7 or 14 days produced sensitization. Sensitization was also observed in the control groups, perhaps as a result of the intermittent schedule of HAL injections given during the dose-response tests. Sensitization to HAL was not accompanied by changes in sensitivity to amphetamine. The results of this experiment are consistent with those of other studies in showing that the behavioral effects of neuroleptics are strongly influenced by the schedule of injections. In addition, evidence is presented that sensitization to HAL-induced hypophagia is contingent on behavioral experience under the drug.

Behavioural and biochemical effects of subchronic treatment with raclopride in the rat: tolerance and brain monoamine receptor sensitivity

Male Sprague-Dawley rats were treated with the dopamine (DA) D2 receptor blocking agent raclopride 0.5 or 8.0 mg kg-1 subcutaneously (1.0 and 16.0 mumol kg-1, respectively), twice daily for 21 days. The animals treated with raclopride gained weight at the same rate as saline controls, and gross observation did not indicate any behavioural abnormalities due to the subchronic raclopride treatment. Possible changes in brain DA receptor sensitivity due to prolonged blockade of DA receptors were evaluated in behavioural and biochemical models. There were no effects on locomotor activity, as observed by means of photobeam-equipped activity cages, 24 hr or 72 hr after withdrawal of 0.5 or 8.0 mg kg-1 subchronic raclopride treatment. Twenty-four hr after withdrawal of the raclopride treatment there was an increased post-synaptic DA receptor sensitivity as evidenced by increased behavioural and biochemical responses to apomorphine, and by an attenuated response to acute raclopride treatment, 0.1 mg kg-1. Thus, there was an increase in locomotor activity by the apomorphine treatment in animals pretreated with the 8 mg kg-1 dose, as compared to the response obtained in saline controls. Furthermore, the suppression of locomotor activity in saline controls produced by acute raclopride treatment was dose-dependently antagonized by the raclopride pretreatment and this also applied to the increase in striatal DOPAC levels produced by acute raclopride treatment. Finally, there was an increased DA receptor sensitivity presynaptically as evidenced by an enhanced effect on striatal DOPA levels by apomorphine in rats treated with NSD 1015 and reserpine.(ABSTRACT TRUNCATED AT 250 WORDS)

Clozapine fails to prevent the development of haloperidol-induced behavioral hypersensitivity in a cotreatment paradigm

We have previously established that chronic cotreatments involving antimuscarinic agents and haloperidol attenuate the development of behavioral hypersensitivity without affecting dopamine receptor proliferation. The antipsychotic agent clozapine also has significant antimuscarinic activity and was coadministered with haloperidol in rats for 2 months to determine if it would similarly attenuate the development of hypersensitivity. Clozapine or chlorpromazine cotreatment, unlike thioridazine cotreatment, did not attenuate the development of haloperidol-induced behavioral hypersensitivity. Clozapine or thioridazine cotreatment also failed to prevent the development of haloperidol-induced D2 receptor proliferation, whereas chlorpromazine cotreatment enhanced D2 receptor proliferation relative to haloperidol-treated animals. Alterations in dopamine biochemistry in the striatum or nucleus accumbens could not explain this dissociation between behavioral hypersensitivity and dopamine receptor proliferation. It is therefore hypothesized that dopamine receptor proliferation is permissive for behavioral hypersensitivity and that factors in addition to alterations in dopamine function contribute to the expression of dopamine hypersensitivity states.