Differential ability of tachykinin NK-1 and NK-2 agonists to produce scratching and grooming behaviours in mice

Potent and selective NK-1 and NK-2 agonists as well as compounds with lower selectivity and affinity for NK-1 binding sites were compared in their ability to produce scratching and grooming behaviours when injected intracerebroventricularly in mice. Septide, an agonist with a low affinity for NK-1 binding sites, [Sar⁹, Met(O₂)¹¹]SP and to a lesser extent [Pro⁹]SP, two potent and selective NK-1 agonists were the most effective drugs in stimulating these behaviours. Only high doses of [Apa^9,10]SP and [Lys⁵, Tyr⁷, Pro⁸]NKA(4–10), two agonists with low affinity for NK-1 binding sites, produced scratching and grooming responses. Similarly, only high doses of [Lys⁵, MeLeu⁹, NLe¹⁰]NKA(4–10), a potent NK-2 agonist, produced grooming behaviour. When coinjected with the endopeptidase enzyme inhibitor phosphoramidon, the effects of [Apa^9,10]SP, [Lys⁵, Tyr⁷, Pro⁸]NKA(4–10) and [Pro⁹]SP were markedly enhanced. Analyses of the potency of the different agents to displace ³H-SP binding in mouse subcortical structures revealed that the affinities of the agonists for NK-1 receptors are similar to those previously reported in rat brain. The efficacy of the agonists at producing behavioural responses was not equivalent to their potency to bind to central NK-1 receptors. These findings therefore suggest that a stimulation of NK-1 but also non classical NK-1 receptors are involved in the induction of scratching and grooming behaviours.     

Modulation of dopamine D1-mediated turning behavior and striatal c-fos expression by the substantia nigra

In order to study the possible contribution of the substantia nigra (SN) in the positive interaction between dopamine D₁ receptor agonists and glutamate antagonists in unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, the effect of the D₁ agonist, SKF 38393, was studied in combination with intranigral infusions of glutamate antagonists of the NMDA (MK 801, CPP) or AMPA (NBQX) type of receptor. Local infusion into the SN of the 6-OHDA lesioned side of MK 801, CPP or NBQX at doses inducing no or minimal behavioral effects significantly increased the turning behavior and the expression of c-fos induced, in the lesioned caudate-putamen (CPu), by a parenteral administration of SKF 38393. The same result was obtained after intra-SN infusion of the GABA agonist, muscimol. High doses of MK 801, CPP or muscimol infused into the SN produced intense contralateral turning per se and induced a sparse c-fos expression in the lesioned CPu which was antagonized by parenteral administration of MK 801. The results indicate that a depression of SN pars reticulata efferent neurons potentiates D₁-mediated responses and suggest that this area may play a role in the positive interaction between glutamate antagonists and D₁ receptor agonists. © 1995 Wiley-Liss, Inc.     

Lesion of the substantia nigra pars compacta downregulates striatal glutamate receptor subunit mRNA expression

This is a study of the effect of the unilateral administration of dopamine (DA) in the pars compacta of the substantia nigra (SN) of the rat on striatal glutamate receptor subunit (GluR1, GluR2 and NMDAR1) gene expression determined by in situ hybridization. The location of the nigral lesion was determined by tyrosine hydroxylase (TH) immunohistochemistry and its extent by the striatal DA and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations. The DA-induced lesions produce significant bilateral reductions in the expression of GluR1 and NMDAR1 subunit mRNA in the medio-lateral striatum, whereas the expression of striatal GluR2 receptors was not changed. The reduction in GluR1 and NMDAR1 subunit mRNA may be the consequence of glutamatergic hyperactivity developed in the presence of a damaged nigro-striatal system and these may be associated with the genesis of some neurodegenerative diseases.     

Substantia nigra pars reticulata lesion induces preconvulsive behavior and changes in glutamate receptor gene expression in the rat brain

The substantia nigra pars reticulata (SNpr) has been proposed to play an important role in the control of the propagation and/or the generation of epileptic seizures. Earlier studies have shown differential effects of the lesion of the SNpr on seizure genesis that demonstrated a regional difference in the anterior and posterior parts of the SNpr in preconvulsive behavior induced by unilateral reticulata injection of dopamine (DA). This study was aimed to investigate some of the underlying mechanisms of the preconvulsive behavior elicited by unilateral SNpr DA injection by the study of changes in the gene expression of glutamate receptor subunits (GluR1, GluR2 and NMDAR1) and of changes in animal behavior following coinfusion of DA and a DA D1 antagonist SCH 23390 into the SNpr. Unilateral injection of exogenous DA into the anterior region of the SNpr induced rapid and short lasting preconvulsive behavior up to wet dog shakes stage and a significant reduction of gene expression for GluR1, GluR2 and NMDAR1 subunits in rat hippocampal subfields including CA1 through CA4 and dentate gyrus (DG) at 1 day after nigral DA injection. The effect was long lasting and persisted for at least 3 weeks. Both preconvulsive behavior and downregulation of glutamate receptor subunit genes were completely blocked by simultaneous coinfusion of DA and SCH 23390. The results suggest, for the first time, that DA D1 receptor in the SNpr may mediate the nigral-involved seizure development. Glutamate desensitization, and/or selective early neuronal damage might be responsible for the downregulation of glutamate receptor subunits by transient preconvulsive activity.     

胚胎黑质移植对帕金森病鼠纹状体中多巴胺受体敏感性的影响

大鼠纹状体中多巴胺受体介导的C－fos基因的表达与多巴胺D1受体的超敏现象有关。本实验在鼠胚胎黑质细胞植入帕金森病大鼠模型纹状体后第12周,用免疫组化法检测阿朴吗啡诱发的C－fos蛋白,同时取相邻切片进行酷氨酸羟化酶检测,结果经图像分析发现胚胎黑质移植,能显著减少移植侧纹状体中C－fos的表达量,说明胚胎黑质移植能够纠正多巴胶受体的超敏现象。除此之外,还发现C－fos减少的区域明显超过相邻切片酷氨酸羟化酶免疫阳性区域,表明细胞移植对超敏的多巴胺受体的影响范围大大超过了其诱发宿主残存多巴胺神经元再生的范围。     

Localization of striatal and nigral tachykinin receptors in the rat

The effects of lesioning mesostriatal dopamine projections or striatal neurons on tachykinin binding in the basal ganglia were assessed in the rat. 6-Hydroxydopamine lesions of the medial forebrain bundle destroyed striatal dopamine terminals as assessed by [³H]mazindol autoradiography, but did not significantly affect the binding of NK-1 ([³H][Sar⁹, Met(O₂)¹¹]substance P) or NK-3 ([³H]senktide) tachykinin ligands in the striatum. 6-Hydroxydopamine lesions significantly reduced NK-3 binding in the substantia nigra pars compacta, but not the ventral tegmental area. In contrast, striatal quinolinic acid lesions reduced both NK-1 and NK-3 binding in the striatum, but failed to affect NK-3 binding in the substantia nigra. These findings suggest that both NK-1 and NK-3 receptors within the striatum are predominantly post-synaptic with respect to dopamine neurons, whereas nigral NK-3 receptors are located on dopaminergic neurons.     

Production of interleukin-1 by microglia in response to substance P: role for a non-classical NK-1 receptor

Substance P (SP) is a central and peripheral neurotransmitter which has been found in multiple sclerosis plaques. SP stimulates peripheral immune cells and may play a role in some chronic inflammatory diseases. Human peripheral monocyte/macrophages have been shown to produce the inflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor α (TNFα) in response to SP. Therefore, in this study we examined rat brain microglia for the presence of SP receptors and production of IL-1 and TNFα in response to SP. Microglia had 4900±950(mean ± SE) receptors per cell fitting a two-site model. Four percent of these were high-affinity receptors with a K_d of 8.2 × 10⁻⁸ M ± 3.6 × 10⁻⁸ M (mean ± SE), and 96% of them were low-affinity receptors with a K_d of 2.1 × 10⁻⁶ M ± 5.2 × 10⁻⁷ M (mean ± SE). Competitive studies with CP 96,345 and other SP analogs demonstrate these to be non-classical NK-1 receptors. SP alone did not stimulate IL-1 or TNFα production. However, SP in synergy with lipopolysaccharide (LPS) quadrupled IL-1 production compared to LPS alone, but did not affect TNFα production. These results have implications for certain inflammatory conditions in the central nervous system.     

Striatal dopamine innervation and receptor density: regional effects of the weaver mutation

Mice homozygous for the autosomal recesive gene weaver (wv) exhibit a regionally specific depletion of forebrain dopamine (DA). DA is reduced approximately 70% in the dorsal striatum of homozygotes (wv/wv) relative to heterozygous (+/wv) controls while DA content in ventral striatum is relatively unchanged. The goal of the present study was to determine the regional effects of the weaver mutation on striatal DA receptors and DA uptake sites using quantitative autoradiography. Catecholamine histofluorescence was used to examine midbrain DA-containing cell bodies. Compared to behaviorally normal (+/-) littermates, the binding of [³H]spiroperidol to D₂ sites was significantly increased in the dorsal but not ventral striatum of wv/wv mice. Binding of the D₁ ligand, [³H]SCH23390, was significantly decreased throughout the striatum of wv/wv mice. The binding of [³H]mazindol to DA uptake sites was dramatically reduced in all wv/wv striatal regions except the ventrolateral portion. Compared to +/-littermates, wv/wv mice had far fewer fluorescent cell bodies in the substantia nigra and a less pronounced reduction of ventral tegmental area fluorescent somata. These findings support the hypothesis that heterogeneities exist in the genetic control of the mesotelencephalic DA system. The results underscore the usefulness of the weaver mouse in the study of mesostriatal sub-systems, receptor regulation, and potentially as a model of human neuropathologies that affect distinct populations of cells in the mesotelecephalic system.     

Small sensory neurons in the rat dorsal root ganglia express functional NK-1 tachykinin receptor

The tachykinins substance P (SP) and neurokinin A, released by the C-type primary afferent fibre terminals of the small dorsal root ganglion (DRG) neurons, play important roles in spinal nociception. By means of non-radioactive in situ hybridization and whole-cell recording, we showed that the small rat DRG neurons also express the NK-1 tachykinin receptor. In situ hybridization demonstrated that the positive neurons in rat DRG sections were mainly small cells (85.9%) with diameters less than 25 μm. The remaining positive neurons (14.1%) were cells with medium diameters between 26 and 40 μm. No positive large neurons (diameters > 40 μm) were observed. Expression in small DRG neurons (diameter < 21 μm) was confirmed by in situ hybridization of isolated cells, which were demonstrated to express NK-1 receptor mRNA at a very high frequency (> 90% of small DRG neurons) and therefore were subjected to whole-cell recording. In 57 of 61 cells recorded, SP or the selective NK-1 receptor agonist [Sar⁹, Met(O2)¹¹]SP (Sar-SP, 1 or 2 μm ) produced a delayed vibrating inward current (50–300 nA) with a long duration of 0.5–2 h. These currents were blocked by co-application of the NK-1 receptor antagonist L-668, 169 (1 μm ), but were not affected by the NK-2 antagonist L-659, 877 (2 μm ). Both current-clamp recording and cell-attached single-channel recording demonstrated that the long-lasting response was due to the opening of a channel with an inward current. Employment of non-Ca²⁺ and Ca²⁺ + choline solutions revealed that this channel might be a Ca²⁺-permeable, non-selective cation channel. The prolonged NK-1 tachykinin response exhibited extreme desensitization. This work suggests that presynaptic NK-1 autoreceptors may be present on the primary afferent terminals in the spinal cord, where they could contribute to the chronic pain and hyperalgesia.     

Ultrastructural localization of D1 dopamine receptor immunoreactivity in rat striatonigral neurons and its relation with dopaminergic innervation

We have investigated by immunohistochemistry the cellular and subcellular distribution of the D1 dopamine receptor (DIR) in the rat striatonigral complex and its relation with the dopaminergic innervation. In the striatum, single pre-embedding immunoperoxidase and immunogold labeling demonstrate that D1R is mainly located on dendritic shafts and spines of spiny dendrites. D1R is also found in association with the plasma membrane of half of the perikarya of medium spiny neurons. Double labeling experiments allowing the simultaneous detection of D1R and of tyrosine hydroxylase (TH) demonstrate that D1R distribution does not match dopamine innervation: a majority of the receptors is located at sites distant from dopamine profiles and there is no significant D1R enrichment at sites of membrane appositions between dopamine and D1R profiles. In the substantia nigra, D1R is located at pre-synaptic sites on small diameter axons which are not in contact with TH-positive elements, and on terminal boutons forming symmetrical synapses on TH-positive or negative dendrites. These data demonstrate abundance and wide distribution of D1R at various extrasynaptic sites in the striatum and the substantia nigra, bringing strong evidence of anatomical basis for dopamine non-synaptic volume transmission in the rat striatonigral complex.     

Pharmacological characterization of the behavioural syndrome induced by the NK-3 tachykinin agonist senktide in rodents: evidence for mediation by endogenous 5-HT.

The effects of various manipulations of brain 5-HT mechanisms on the behavioural responses induced by the selective NK-3 tachykinin agonist senktide in rodents were assessed. Senktide elicited wet dog shakes in the rat which were attenuated by the 5-HT1C/2 antagonist mianserin and the selective 5-HT2 antagonist altanserin. Senktide-induced forepaw treading was stereospecifically attenuated by the 5-HT1A + B antagonist (-)-alprenolol. Senktide also elicited chewing mouth movements and yawning, which were unaffected by mianserin, altanserin, (+)- or (-)-alprenolol, or the selective 5-HT3 antagonist ICS 205-930, but attenuated by the muscarinic antagonist scopolamine. Penile grooming elicited by senktide was attenuated by mianserin, but was unaffected by the other antagonists. Senktide-induced wet dog shakes were enhanced by the 5-HT reuptake inhibitors citalopram and fluoxetine, suppressed by the monoamine oxidase (MAO)-B inhibitor pargyline, but unaffected by the MAO-A inhibitor clorgyline. Forepaw treading was potentiated by citalopram and clorgyline, but not significantly altered by fluoxetine or pargyline. Depletion of 5-HT by p-chlorophenylalanine (PCPA) in the rat attenuated senktide-induced wet dog shakes and forepaw treading. Neither PCPA nor 5,7-dihydroxytryptamine affected senktide-induced behaviours in the mouse, but the degree of brain 5-HT depletion caused by these treatments in mice was relatively small. These findings indicate that stimulation of NK-3 tachykinin receptors by senktide results in a complex behavioural syndrome which is mediated by multiple 5-HT receptors, and dependent upon intact stores of endogenous 5-HT. Independent stimulation of brain cholinergic mechanisms by senktide is also confirmed.     

Dopamine antagonists induce fos-like-immunoreactivity in the substantia nigra and entopeduncular nucleus of the rat

Injections of the D₂ receptor antagonists haloperidol (0.5–8 mg/kg) and metoclopramide (6.25–50 mg/kg) in rats resulted in a dose dependent induction of Fos-like-immunoreactivity in the rostral portion of the entopeduncular nucleus (EPN) and in the medial portion of the pars reticulata of the substantia nigra (SNpr). Nigral staining occurred exclusively in neurons which were not immunoreactive for tyrosine hydroxylase and could be antagonized by pretreatment with the anticholinergic drug scopolamine (3 mg/kg). Effects were much less pronounced following injections of the selective D1 antagonist SCH-23390 (2–8 mg/kg). No staining could be observed following administration of the 5HT₃ antagonist MDL-72222 (10 mg/kg) or the 5HT₁/5HT₂ antagonist metergoline (5 mg/kg), suggesting that the effects observed with dopamine antagonists were not secondary to actions at serotonin receptors. These results are consistant with the hypothesis that blockade of dopamine receptors results in a disinhibition of cells within the SNpr and EPN and further suggest that examination of immediate-early gene expression may provide a useful tool for studying the extrastriatal circuitry engaged by manipulations of dopaminergic transmission.     

Neurophysiological investigation of effects of the D-1 agonist SKF 38393 on tonic activity of substantia nigra dopamine neurons

The effects of the D-1 agonist SKF 38393 on tonic activity of rat substantia nigra pars compacta dopamine neurons were studied using extracellular, single-unit recording techniques. Unlike nonselective D-1/D-2 dopamine agonists or the D-2 agonist quinpirole, SKF 38393 did not inhibit dopamine neuronal activity when applied iontophoretically or when administered intravenously in doses up to 20 mg/kg to chloral hydrate-anesthetized rats. Moreover, pretreatment with SKF 38393 did not alter the inhibitory response of these neurons to apomorphine or the D-2 agonist quinpirole. However, in locally anesthetized, gallamine-treated, artificially respired rats, dopamine cell activity was significantly altered by i.v. administration of SKF 38393; firing rate increases and decreases were observed. Administration of the inactive enantiomer of SKF 38393, S-SKF 38393, did not induce similar changes in parallel experiments. These results support the idea that unlike D-2 autoreceptor stimulation, D-1 receptor stimulation does not exert a direct local effect on dopamine neurons in the substantia nigra pars compacta and suggest that D-1 receptor stimulation at sites postsynaptic to the dopamine cells may indirectly affect the activity of some dopamine neurons through long-loop feedback mechanisms.     

Excitation of type II caudate neurons by systemic administration of dopamine agonists

Using chloral hydrate anesthetized rats, dopamine (DA) agonists were evaluated for their systemic effects on firing rates of DA neurons in rat substantia nigra pars compacta (SNPC) and postsynaptic type 11 neurons in the anterior caudate nucleus (CN), the major projection area for SNPC DA neurons. Intravenous injections of the indirect DA agonistd-amphetamine, but notl-amphetamine, excited spontaneously active CN neurons by a haloperidol-sensitive mechanism. Doses to achieve CN excitation were similar to those required to inhibit SNPC firing. This data is consistent with the theory thatd-amphetamine inhibition of SNPC DA neurons is dependent upon neuronal negative feedback pathways originating in CN. Intravenous injections of direct agonists apomorphine, which stimulates all DA receptor subtypes, and quinpirole, which only stimulates D₂ receptor subtypes, increased firing rates of spontaneously active CN neurons, but only at doses above those inhibiting firing rates of SNPC neurons. SKF 38393, a selective D₁ agonist, had little or no effect on the firing rates of DA neurons in SNPC, on type II anterior CN neurons, or on the effects of quinpirole on anterior CN neurons. It is concluded that excitation of type II anterior CN neurons is mediated via receptors of the D₂ subfamily. These results are compared to those reported elsewhere for type I CN neurons, and the possible relevance of these results for the role of DA in motor function is discussed.     

Presynaptic and postsynaptic D1 dopamine receptors in the nigrostriatal system of the rat brain: a quantitative autoradiographic study using the selective D1 antagonist [H]SCH 23390

Ibotenic acid lesions of the caudate-putamen in rat brain resulted in dramatic reductions in [³H]SCH 23390 binding in both the ipsilateral caudate-putamen and substantia nigra reticulata as assessed by quantitative autoradiography. Nigral ibotenic acid and 6-hydroxydopamine lesions did not significantly alter the binding in either structure. This indicates that D₁ receptors in the caudate-putamen are postsynaptic on striatal neurons, while those in the substantia nigra reticulata are presynaptic on nerve terminals originating in the caudate-putamen.     

ERK1／2在左旋多巴诱导的异动症发生机制中的作用

目的研究细胞外调节激酶（ERK1／2）在左旋多巴诱导的异动症（LID）发生机制中的作用。方法将SD大鼠分为5组：正常对照组、帕金森病（PD）组、LID组、LID＋SCH23390组和非LID组，分别观察各组行为学变化，并用免疫组化方法测定大鼠纹状体区ERK1／2及其活化形式p—ERK1／2表达水平。结果多巴胺D1受体阻断剂SCH23390可以减轻LID大鼠行为学异常；LID组和非LID组ERK1／2的表达无显著性差异，而LID组p-ERK1／2的表达较非LID组和PD组明显增加，SCH23390使其表达下降。结论ERKI／2是LID大鼠纹状体内直接输出通路上的重要信号分子，其活化参与了异动症的发生。     

Lasting increase in D1 dopamine receptors in the lateral part of the substantia nigra pars reticulata after subchronic methamphetamine administration

To examine the possible involvement of D₁ dopamine receptors in behavioral sensitization induced by subchronic methamphetamine (MAP) administration, regional D₁ receptors labeled with [³H]SCH 23390 were examined using binding assay and quantitative autoradiography. Rats received 4 mg/kg/day MAP (i.p.) for 14 days, and were decapitated after an abstinence period of 24 h, 7 days or 21 days. In MAP-treated rats, a significant decrease in K_d in the mesolimbic area was observed 24 h but not 7 days after the last injection. Neither K_d nor B_max changed in the striatum or medial prefrontal cortex of MAP-treated rats after any period of abstinence. Autoradiography revealed a significant increase in specific [³H]SCH 22390 binding in the lateral part of the substantia nigra pars reticulata (SNr) of MAP-treated rats. Since this increase lasted up to 21 days after cessation of subchronic MAP administration, it is suggested that lasting increase in the nigral D₁ receptors may be associated with the biological changes underlying MAP-induced behavioral sensitization.     

The selective neurokinin (NK)(1) antagonist,GR205,171, stereospecifically enhances mesocortical dopaminergic transmission in the rat: a combined dialysis and electrophysiological study

Upon acute, systemic administration, the selective, non-peptidergic NK(1) receptor antagonist, GR205,171, dose-dependently enhanced the firing rate of ventrotegmental dopaminergic neurones. Dialysate levels of dopamine were increased in the frontal cortex, but not in the striatum and nucleus accumbens, of conscious rats. These actions were stereospecific in that its less-active isomer, GR226,206, was ineffective. Further, they were selective for dopaminergic pathways inasmuch as the firing rate of dorsal raphe serotonergic neurones and dialysate levels of serotonin were unaffected by GR205,171. Activation of mesocortical dopaminergic pathways may be involved in the influence of NK(1) antagonists upon mood.     

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.     

Intranigral GR-113808, a selective 5-HT4 receptor antagonist, attenuates morphine-stimulated dopamine release in the rat striatum

GR-113808, a potent and selective 5-HT₄ receptor antagonist, was infused through a microdialysis probe into the striatum and nucleus accumbens of awake rats, and basal and morphine-stimulated extracellular concentrations of dopamine (DA) were measured in these regions. At 1 and 10 μM GR-113808 did not effect the extracellular concentrations of DA in either region and 100 μM significantly reduced dialysate DA only in the striatum. A subcutaneous dose of 5 mg/kg morphine significantly raised extracellular concentrations of DA in the striatum and nucleus accumbens from 60 to 120 min after injection and the effect was not modified by 10 μM GR-113808 infused through the probe 20 min before and for 60 min after morphine. Bilateral injections of GR-113808 (1, 2.5 and 10 μg/0.5 μl) in the substantia nigra pars compacta did not affect dialysate DA in the striatum, except for a significant increase 120 min after the injection of 10 μg but the highest dose of GR-113808 prevented the increase of striatal DA caused by 5 mg/kg morphine s.c. The results suggest that 5-HT₄ receptors in the substantia nigra modulate the activity of the dopaminergic nigrostriatal system only when the neurons are activated.