Neuroleptic treatment induces region-specific changes in levels of neurokinin A and substance P in rat brain

The effects of haloperidol treatment on the distribution of NK1 receptor immunoreactive neurons in guinea-pig brain

Previous studies have observed increased tachykinin NK(1) receptor immunoreactivity (NK(1)-IR) in the prefrontal cortex in subjects with schizophrenia. Since the subjects were medicated the possibility of a treatment effect could not be excluded. Thus, the present study was undertaken to determine the effect of chronic treatment with the antipsychotic drug, haloperidol, on the distribution of NK(1)-IR neurons in the guinea-pig brain. Guinea pigs were treated each day for 21 days with either haloperidol (1mg/kg) or vehicle and the brains were then processed for immunohistochemistry using an NK(1) receptor-specific polyclonal antibody. NK(1)-IR neurons and fibres were abundant in the forebrain cortex and caudate putamen and more sparsely distributed in a number of other brain regions. The relative density of NK(1)-IR neurons was significantly increased in the forebrain cortex, but not in the caudate putamen in guinea pigs treated with haloperidol. This study has shown that haloperidol causes region-specific changes to the density of NK(1)-IR neurons. Whether these changes are related to the therapeutic effects or to the side effects of haloperidol in individuals with schizophrenia, remains to be determined.

Autoradiographic distribution of tachykinin NK2 binding sites in the rat brain: comparison with NK1 and NK3 binding sites

The autoradiographic distribution of tachykinin NK(2) binding sites was determined in the adult rat brain using [(125)I]neurokinin A in the presence of either senktide (NK(3) agonist) and [Pro(9)]substance P (NK(1) agonist) or senktide and SR 140333 (NK(1) antagonist). Indeed, this radioligand labels two subtypes of NK(1) binding sites (which present a high affinity not only for SP but also for neurokinin A, neuropeptide K and neuropeptide gamma) as well as NK(3) binding sites. The distribution of NK(2) binding sites was also compared with those of NK(1) and NK(3) binding sites, these sites being labeled with [(125)I]Bolton and Hunter substance P and [(125)I]Bolton and Hunter eledoisin, respectively. In agreement with our results obtained with membranes from various brain structures, NK(2)-sensitive [(125)I]neurokinin A labeling was mainly observed in few structures including the dorsal and ventral hippocampus, the septum, the thalamus and the prefrontal cortex. The density of NK(2) binding sites was weak when compared with those of NK(1) and NK(3) binding sites. Marked differences were observed in the distributions of NK(1), NK(2) and NK(3) binding sites. These results are discussed taking into consideration differences or similarities between the distributions of NK(2)-sensitive [(125)I]neurokinin A binding sites and of their endogenous ligands (neurokinin A, neuropeptide K and neuropeptide gamma) but also local NK(2) agonist responses blocked by NK(2) antagonists. Insights on the roles of endogenous tachykinins in several brain functions are also discussed on the basis of the respective distributions of different neurokinin binding sites.

Effect of chronic haloperidol treatment on synaptic protein mRNAs in the rat brain

Chronic haloperidol treatment caused significant decreases in the levels of synaptotagmin I and IV, synaptobrevin II, syntaxin 1A and Rab 3A mRNAs in the nucleus accumbens but not in the prefrontal cortex medial field, striatum, substantia nigra and ventral tegmental area. No significant changes in SNAP 25 and synaptophysin mRNA levels were observed in any brain region examined. The reduced expression of synaptic proteins may be related to haloperidol-induced depolarization block of mesolimbic dopamine neurons.

Effect of chronic antipsychotic drug treatment on preprosomatostatin and preprotachykinin A mRNA levels in the medial prefrontal cortex, the nucleus accumbens and the caudate putamen of the rat

In situ hybridization histochemistry was used to study the expression of preprosomatostatin (PPSOM) and preprotachykinin A (PPT-A) mRNA in the medial prefrontal cortex (mPFC), the nucleus accumbens (NAC) and the caudate putamen (CP) of the rat after chronic (21 days) treatment with the classical antipsychotic drug haloperidol (1 mg/kg i.p.), the atypical antipsychotic drugs clozapine (15 mg/kg i.p.) and amperozide (5 mg/kg i.p.), and the selective dopamine (DA)-D2/D3 receptor antagonist raclopride (2 mg/kg i.p.). Whereas amperozide markedly elevated the numerical density of PPSOM mRNA expressing neurons in the mPFC (52%), the other drugs did not significantly affect PPSOM mRNA levels in any of the brain regions studied. Amperozide also altered PPT-A mRNA expression in the mPFC, i.e. a decrease (22%) was found. Of the other drugs tested only haloperidol significantly decreased PPT-A mRNA levels in the NAC shell (14%), in the dorso-lateral CP (19%) and in the medial CP (15%). In view of the differences between amperozide and the other drugs studied, as regards both pre-clinical and clinical characteristics, we suggest that the specific effects of amperozide on PPSOM and PPT-A mRNA in the mPFC may be related to its 5-HT releasing action in the frontal cortex, an effect possibly caused by its alpha2-adrenoceptor blocking activity. This effect, in turn, may be related to an antidepressant-like action that this compound exhibits in animal studies. The decrease in PPT-A mRNA levels seen after the haloperidol treatment is probably due to its potent DA-D2 receptor antagonism and may be related to side-effects, rather than therapeutic effects of this drug.

The effect of haloperidol on met-enkephalin, beta-endorphin, cholecystokinin and substance P in the pituitary, the hypothalamus and the striatum of rats during aging

1. Haloperidol increased the Met-enk level in the striatum at all age groups. However, the Met-enk level was decreased in AL of young and middle-aged rats by the drug. 2. Haloperidol elevated the beta-end level in AL and CCK level in NIL in young rats only. 3. The SP content in NIL was decreased by haloperidol in all age groups. 4. With regard to the effect of aging, Met-enk level in AL of middle-aged rats was higher than that in young rats. The beta-end level in AL also increased in old rats. 5. Aging modified the haloperidol effect on beta-end level in AL and CCK level in NIL as the effect was only observed in young rats. 6. In addition, aging caused a blunted response of Met-enk level to haloperidol in the striatum but an increased response of SP content to haloperidol in the NIL.

Amphetamine and haloperidol modulate preprotachykinin A mRNA expression in rat nucleus accumbens and caudate-putamen

In situ hybridization was used to measure the effect of repeated amphetamine (1.5 mg/kg) and haloperidol (0.5 mg/kg) treatment for 7 days on the expression of preprotachykinin A (PPT-A) mRNA in rat nucleus accumbens (Acb) and caudate-putamen (CPu). Amphetamine elevated the level of PPT-A mRNA in Acb, but not in CPu. Haloperidol decreased the levels in Acb shell and CPu, but not in Acb core. Haloperidol injected together with amphetamine, prevented the amphetamine-induced increase in PPT-A mRNA expression in both Acb core and shell.

Effects of haloperidol and clozapine on preprotachykinin-A messenger RNA, tachykinin tissue levels, release and neurokinin-1 receptors in the striato-nigral system

The effects of haloperidol and clozapine on tachykinin tissue levels, preprotachykinin-A messenger RNA, spontaneous and potassium-evoked tachykinin release, dopamine D2 receptors, and [125I]Bolton-Hunter-substance P binding sites in the striato-nigral system were examined. Chronic administration (10 days) of the dopamine receptor antagonist haloperidol (2 mg/kg i.p.) significantly decreased tissue levels of substance P like-immunoreactivity and neurokinin A like-immunoreactivity in the striatum and the substantia nigra. The corresponding preprotachykinin-A mRNA was decreased in the striatum. Haloperidol did not affect the potassium-evoked tachykinin release in the substantia nigra but significantly increased the spontaneous release. Haloperidol increased the number of D2-receptors but left [125I]Bolton-Hunter-substance P binding sites, representing neurokinin 1 (NK-1) receptors, as determined by competition experiments with selective ligands, unchanged. Clozapine (30 mg/kg, i.m.) did not influence nigral and striatal tachykinin tissue levels, preprotachykinin-A mRNA and potassium-evoked release or spontaneous efflux in the substantia nigra, or D2-receptors and [125I]Bolton-Hunter-substance P binding sites. The present data indicate that neuroleptics influence the striato-nigral tachykinin system in different ways. Tachykinins may, therefore, contribute to the therapeutic and/or untoward effects of certain neuroleptic drugs.

Studies on brain monoamine and neuropeptide systems after neonatal intracerebroventricular 6-hydroxydopamine treatment

In order to study the effects of a neonatal dopamine lesion on dopaminergic, serotonergic and peptidergic systems, Sprague-Dawley rats were treated by intracerebroventricular administration of 6-hydroxydopamine (100 micrograms, days 3 and 6) following desipramine pretreatment (25 mg/kg s.c.). At 60-70 days postnatally a profound reduction of dopamine- and 3,4-dihydroxyphenylacetic acid levels was found in striatal and limbic forebrain regions concomitant with an extensive loss of tyrosine hydroxylase-immunoreactive fibers, while no significant alteration in noradrenaline levels was seen. A marked loss of tyrosine hydroxylase-immunoreactive cell profiles was also observed in the substantia nigra and ventral tegmental area in mesencephalon. In striatum, but not in other regions analysed, an almost 100% increase in serotonin levels and serotonin-immunoreactive fiber density was observed following 6-hydroxydopamine treatment. However, the number of serotonin-immunoreactive cell profiles in the median and dorsal raphe nuclei was not altered. The 6-hydroxydopamine treatment also led to reductions in substance P levels in striatum, nucleus accumbens and ventral mesencephalon. The cholecystokinin level in nucleus accumbens and neurotensin level in ventral mesencephalon were also reduced. A neonatal intracerebroventricular 6-hydroxydopamine treatment thus leads to a lesion of dopamine neurons in the mesencephalon with extensive loss of dopamine fibers in several forebrain areas, while localized serotonin fiber sprouting is induced in striatum. Furthermore, concomitant reductions of the levels of peptides related to the dopamine system occur following the 6-hydroxydopamine treatment. Behavioral disturbances such as hyperactivity and cognitive deficiencies occurring after a dopamine lesion early in life might therefore be due to plastic alterations in several different transmitter/neuromodulator systems as a direct or indirect consequence of the lesion.

Pathogenesis and treatment of neuroleptic malignant syndrome

1. Neuroleptic drugs (antipsychotics) produce numerous side effects which include serious extrapyramidal symptoms consisting of akathisia, dystonia, neuroleptic malignant syndrome, parkinsonian reactions such as postural abnormality, tremor, akinesia or bradykinesia, rigidity, and tardive dyskinesia. 2. Among the complications of neuroleptic chemotherapy, the most serious and potentially fatal complication is malignant syndrome, which is characterized by extreme hyperthermia, "lead pipe" skeletal muscle rigidity causing dyspnea, dysphagia, and rhabdomyolysis, autonomic instability, fluctuating consciousness, leukocytosis, and elevated creatine phosphokinase. 3. Neuroleptic malignant syndrome should be differentiated from malignant hyperthermia, lethal catatonia, and other pathological states producing some of these same symptoms. 4. In addition to neuroleptics, malignant syndrome has been caused by thymoleptics (antidepressants), metoclopramide (antiemetic), metoclopramide combined with cimetidine, tetrabenazine, overdosage of benzodiazepine, phenelzine, dothiepin and alcohol, and amphetamine. 5. Factors leading to and/or facilitating the emergence of neuroleptic malignant syndromes are reportedly organic brain syndrome, dehydration, exhaustion, external heat load, excessive sympathetic discharge, use of long acting neuroleptics, high doses of neuroleptics, rapid dose titration with neuroleptics, abrupt discontinuation of antiparkinsonism agents, and concurrent lithium therapy. 6. Although, the pathogenesis of neuroleptic malignant syndrome is not understood completely, a blockade of dopaminergic receptors in the hypothalamus, spinal cord and striatum, an alteration of dopaminergic-serotonergic transmission in the body, an enhanced synthesis and action of prostaglandin E1 and E2, and a modification of calcium-mediated signal transduction in the body have been suggested. 7. The treatment of malignant syndrome includes immediate withdrawal of neuroleptic drugs, i.v. infusion of dantrolene, and oral administration of bromocriptine; or alternatively i.v. infusion of dantrolene and the combination of levodopa-carbidopa. 8. Other measures to enhance the therapeutic effectiveness of the aforementioned regimens are to include the use of anticholinergic drugs such as benztropine to enhance the effectiveness of bromocriptine, of lorazepam if catatonic symptoms persist, or of electroconvulsive therapy (ECT) if psychotic symptoms persist. 9. These treatments, however, must be "active" rather than "passive", in order to avert fatalities and/or unfortunate sequelae from this iatrogenic and incompletely understood disease.

Intracerebral microdialysis: I. Experimental studies of diffusion kinetics

Intracerebral microdialysis is a brain perfusion technique in which a tubular, semipermeable membrane perfused with a physiological solution is implanted into a selected brain region. Molecules in the extracellular space diffuse into the perfusate and may be recovered and their concentration determined. Hence, the level of substances such as neurotransmitters may be monitored, and the response to different treatments may be studied. The technique also allows for administration of substances locally to the region of the brain surrounding the perfused tubular membrane. Basic principles of the microdialysis technique are described, and the results from methodological experiments are examined. It is concluded that there is a direct linear relation between the concentration of a molecule in the medium surrounding the dialysis membrane and the concentration measured in the collected perfusate. Relative changes of molecular concentration in brain extracellular space may be calculated even when the molecular diffusion rate is unknown. In addition, a method is presented for calculating the real concentration of a substance in the extracellular space from its concentration in the perfusate. Applied in striatum of rat brain using microdialysis in vivo, the average extracellular concentration of the following substances is estimated to be: substance P, 0.9 nM; dopamine, 1 microM; and dihydroxyphenylacetic acid, 0.05 mM.

D1 dopamine receptor-mediated substance P depletion in the striatonigral neurons of rats subjected to neonatal dopaminergic denervation: implications for self-injurious behavior

The present study examined the influences of dopamine (DA) receptor stimulation on enkephalin (Met5-enkephalin; ME) and tachykinin (substance P; SP) systems of basal ganglia of Sprague-Dawley rats, lesioned as neonates with 6-hydroxydopamine (6-OHDA). It has been proposed that the neonatal 6-OHDA-lesioned rat could serve as a model for the DA deficiency and self-injurious behavior (SIB) observed in the childhood neurological disorder. Lesch-Nyhan syndrome. In agreement with earlier work, the present study found that the neonatal 6-OHDA treatment at 3 days of age, reduced DA and caused an increase in ME and a decrease in SP content in the striatum and substantia nigra, when tested as adults. Administration of the DA precursor, L-dihydroxyphenylalanine (L-DOPA), to lesioned animals, induced SIB; increased DA and DOPAC levels; produced a greater decrease (-64%) in SP levels in the striatum and substantia nigra than was observed with lesion alone (-28%). The L-DOPA-induced decrease in SP levels and the SIB observed in the lesioned animals were blocked by pretreatment with the D1 receptor antagonist, SCH-23390. Moreover, administration of the D1 receptor agonist, SKF-38393, but not the D2 agonist, LY-171555, to lesioned animals mimicked the L-DOPA responses in all respects, except that the agonists did not alter DA or DOPAC levels. None of the DA agonists or antagonists treatments affected lesion-induced increase in ME levels in the striatum. These results indicate for the first time, that SIB precipitated by DA agonists in neonatal dopaminergic denervated animals, is associated with a marked and selective decrease in SP in the striatonigral SP neurons. This process has two components: (a) a retarded development of the SP system due to neonatal dopaminergic denervation: and (b) a depletion of the remaining SP, presumably by enhanced release due to D1 DA receptor-mediated activation of striatonigral SP neurons.

Long-term haloperidol treatment decreases somatostatin binding in rat brain

The effects of short and long-term haloperidol treatment on somatostatin concentration and specific binding in rat cerebral cortex and hippocampus were examined using the binding ligand 125I-Tyr1-somatostatin. Haloperidol treatment did not affect the concentration of somatostatin-like immunoreactivity in the two brain areas. Nevertheless, long-term, and not short-term, haloperidol treatment decreased the number of somatostatin receptors in the cerebral cortex and hippocampus. No significant differences in the apparent binding affinity values were seen after haloperidol treatment. When added at the time of the binding assay haloperidol 34.2 microM produced a 42% and 27% decrease in cerebrocortical and hippocampal membrane somatostatin receptors respectively.

Subchronic haloperidol treatment decreases the in vivo release of tachykinins in rat substantia nigra

Microdialysis combined with sensitive radioimmunoassays was used to measure the in vivo release of substance P (SP) and neurokinin A (NKA) in the rat substantia nigra. The effect of acute and subchronic haloperidol treatment (0.5 mg/kg) on the basal and potassium-evoked release was studied. No significant effect was observed after a single injection. However, pretreatment with haloperidol for 10 days decreased the potassium-induced release of SP and NKA by 25 and 27%, respectively. The basal overflow of NKA was reduced by 29%, while no significant effect could be seen on the basal release of SP.

Amphetamine facilitates the in vivo release of neurokinin A in the nucleus accumbens of the rat

Microdialysis combined with radioimmunoassay was used to measure the release of neurokinin A-like immunoreactivity (NKA-LI) in the rat brain in vivo. The effect of a single dose of amphetamine (2 mg/kg s.c.) on the basal overflow and the potassium-induced release of NKA-LI was assessed in the nucleus accumbens and caudate-putamen. Amphetamine potentiated the potassium-stimulated release of NKA-LI by 71% in the nucleus accumbens, while no significant change was observed in the caudate-putamen. Amphetamine did not affect the basal NKA-LI overflow.

Effects of acute and long-term treatment with methamphetamine on substance P concentration and receptor numbers in the rat brain

To examine biochemical changes in brain substance P (SP) systems associated with development of behavioral sensitization induced by methamphetamine (MAP), regional substance P-like immunoreactivity (SP-LI) and SP receptor binding in the rat brain were measured after acute and long-term MAP administration. Single administration of 8 mg/kg MAP significantly reduced the striatal SP-LI concentration 1 h after the injection. This reduction was blocked by pretreatment with haloperidol. Although repeated administration of 4 mg/kg MAP for 14 consecutive days did not affect the SP-LI concentration in any brain regions including the striatum, it decreased specific SP receptor binding in the striatum and increased those in the frontal cortex. Scatchard analysis of saturation isotherm of specific SP binding revealed that the decreased specific SP binding in the striatum resulted from a decrease in the maximal number (Bmax) of SP receptors and that increased binding in the frontal cortex resulted from an increase in Bmax. These changes in SP receptor binding lasted for at least 7 days. It is emphasized that the persisting changes induced by long-term MAP administration in the SP receptor may contribute to behavioral sensitization to MAP in rats and may be associated with neuronal mechanisms in MAP psychosis.

Comparison between short- and long-term haloperidol administration on somatostatin and substance P concentrations in the rat brain

Neuroleptics influence a variety of putative neurotransmitters in the basal ganglia, including somatostatin and substance P. Most studies have been performed in animals after only 3 or 4 weeks of neuroleptic administration and have seldom examined the effects of withdrawal. To understand better the effects of haloperidol on neuropeptide systems, the effects of short-term (3 weeks) and long-term (8 months) administration, as well as withdrawal from long-term administration of haloperidol, on somatostatin and substance P concentrations were examined in the rat. Short-term haloperidol significantly decreased the concentrations of somatostatin in the caudate-putamen, nucleus accumbens, and ventral tegmental area, and decreased the concentration of substance P in the substantia nigra and the nucleus accumbens. However, long-term administration only decreased the concentration of somatostatin in the nucleus accumbens. In addition, a slight reduction in the concentration of substance P in the medial prefrontal cortex was detected after long-term treatment. After withdrawal from long-term haloperidol administration the concentrations of these peptides did not differ from control values in any of the brain regions examined. These results confirm that dopamine receptor blockade can affect the somatostatin and substance P systems in the basal ganglia and indicate that during long-term administration (8 months) tolerance develops to some of the effects that are observed after shorter (3 weeks) treatment periods.

Microdialysis combined with a sensitive radioimmunoassay. A technique for studying in vivo release of neuropeptides

Microdialysis in combination with radioimmunoassay was used to study in vivo release of neuropeptides in the rat brain. Microdialysis is a novel brain perfusion technique, by which molecules in the extracellular space may be monitored. This study describes the application to neuropeptide research. A radioimmunoassay procedure was adapted so that substance P- and neurokinin A-like immunoreactivity could be measured in samples collected during in vivo release experiments. The detection limits of substance P and neurokinin A were below 0.1 fmol/100-microliters sample and the IC50 approximately 1 fmol/sample for both peptides. Potassium, introduced via the microdialysis probe, was found to induce a concentration-dependent increase of the extracellular concentration of neurokinin A-like immunoreactivity.

Effects of subchronic treatment with imipramine, zimelidine and alaproclate on regional tissue levels of substance P- and neurokinin A/neurokinin B-like immunoreactivity in the brain and spinal cord of the rat

The effects of subchronic (14 day) treatment with the inhibitors at the uptake of monoamines, zimelidine, alaproclate and imipramine, on regional levels of substance P (SP) and other tachykinins in tissue in the central nervous system of the rat were studied by radioimmunoassay. In the ventral spinal cord, in which substance P is known to exist together with 5-hydroxytryptamine (5-HT), in the terminals of descending neurones, treatment with the selective inhibitors of the uptake of 5-HT zimelidine (2 X 10 mumol/kg p.o.) or alaproclate (2 X 10 mumol/kg or 2 X 20 mumol/kg p.o.), increased the level of substance P-like immunoreactivity (SP-LI). The effect of alaproclate appeared to be dose-dependent. After treatment with imipramine (2 X 10 mumol/kg p.o.) only a tendency to increased levels of substance P-like immunoreactivity spinal cord was seen. Treatment with alaproclate, at the highest dose level, also elevated the concentration of neurokinin A/neurokinin B-like immunoreactivity (NKA/NKB-LI) in the ventral spinal cord. In the frontal cortex, in which separate monoaminergic and tachykinin-containing neurones interact, treatment with imipramine reduced the levels of SP-LI and NKA/NKB-LI, while treatment with alaproclate had the opposite effect. In the periaqueductal grey matter, treatment with zimelidine and alaproclate increased the levels of SP-LI and NKA/NKB-LI, while treatment with imipramine increased only the level of NKA/NKB-LI. In conclusion, subchronic treatment of rats with inhibitors of the uptake of monoamines induced changes in levels of tachykinin in frontal cortex, periaqueductal grey and spinal cord. The selective inhibitors of the uptake zimelidine and alaproclate, had similar effects on levels of tachykinin, while the inhibitor of the uptake of 5-HT and noradrenaline, imipramine induced changes in the frontal cortex, which were qualitatively different from the effects of zimelidine and alaproclate. Furthermore, the levels of different tachykinins were not always changed in parallel by the same treatment.

Subchronic haloperidol and sulpiride treatment induces region-specific changes in tissue levels of putative amino acid transmitters in rat brain

The effect of 10 days treatment with haloperidol (0.5 or 2 mg/kg/day) or sulpiride (10 or 100 mg/kg/day) on regional brain tissue levels of GABA, glutamate, aspartate and glutamine was studied in the rat. The GABA levels were increased in the nucleus (nuc.) accumbens and striatum by haloperidol, but not by sulpiride. The glutamate and glutamine levels were increased in the nuc. accumbens by both drugs. The aspartate levels were increased in the nuc. accumbens by sulpiride. Tissue levels of all 4 amino acids studied remained unchanged in the substantia nigra following the drug treatment. These results indicate that dopaminergic activity has a region-specific influence on the utilization of aspartate, glutamate and GABA in rat brain.

Effects of subchronic haloperidol and sulpiride on regional brain dopamine metabolism in the rat

The DOPAC/dopamine and HVA/dopamine ratios in extracted whole tissue were determined to obtain an index of dopaminergic activity in various rat brain regions 24 h following 10 days' treatment with haloperidol (0.5 and 2 mg/kg) or sulpiride (10 and 100 mg/kg). Both neuroleptics caused a reduction in the metabolite/amine ratio in nucl. accumbens but not frontal cortex or substantia nigra. Haloperidol, but not sulpiride significantly reduced the HVA/dopamine ratio in striatum. A region-specific action of neuroleptics on brain dopamine neurons is discussed.

Neurokinin A and substance P in striato-nigral neurons in rat brain

The effect of an ibotenic acid lesion in rostral striatum on tissue levels of neurokinin A and substance P in striatum and substantia nigra was studied in rat brain. A total of 32 micrograms (10 mg/ml) ibotenic acid was injected in four positions to lesion striatal cell bodies rostral to bregma. The neurokinin A level was reduced to a third of the control value in striatum and to less than half of the control level in substantia nigra. Neurokinin A, in addition to substance P, is shown to be possibly present in striato-nigral neurons, which provides further evidence for the existence of a striato-nigral tachykinin pathway.