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A marked rise in 5-S-cysteinyl-dopamine levels in guinea-pig striatum following reserpine treatment.

Reserpine administration (5 mg/kg, i.p.) to guinea pigs resulted in marked and long lasting dopamine (DA) depletion and a rapid, short lasting, increase of 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. A marked and sustained increase of the level of 5-S-cysteinyl-dopamine, which is an adduct presumably formed following autoxidation of DA, started 3-4 h following the DA and DOPAC changes. Only small changes in the levels of the 5-S-cysteinyl adducts of DOPAC and 3,4-dihydroxyphenylalanine (DOPA) were found.

3,4-Dihydroxyphenylacetic Acid↗

Inhibition of reserpine-induced PGO waves in the cat by ergot derivatives.

The number of reserpine-induced PGO waves in the cat is decreased by administration of ergot derivatives. The inhibition is dose-dependent and the various ergot derivatives show differing potencies. The action of the ergot derivatives may result from stimulation of central serotonin receptors. In addition, possible involvement of dopaminergic systems is discussed.

Animals↗

Impaired amylase release from the parotid gland of rats treated with reserpine.

Using an automated system for the analysis of amylase, the release of this enzyme was compared in superfused parotid gland segments from control and reserpine treated rats. Stimulant-evoked amylase release was delayed and of smaller magnitude in the glands of the treated animals and a reduction of the transmembrane K+ gradient caused a smaller and short lasting reduction in Ach-evoked release of amylase in the glands from these animals.

Acetylcholine↗

Electroconvulsive treatment attenuates behavioral response to SKF 38393 in reserpine-treated mice.

Electroconvulsive treatment (ECT) of mice, once daily for 7 days, significantly reduced the stimulation of motor activity induced by the selective dopamine (DA) D1-receptor agonist SKF 38393 (15 mg/kg IP), but significantly increased the motor stimulation by the unselective DA-receptor agonist apomorphine (1.5 mg/kg IP) in reserpine-treated (10 mg/kg IP) mice, when compared to control mice, receiving sham ECT. The results provide a functional correlate to previously observed ECT-induced down-regulation of D1 receptor sites in DA-rich regions of the rodent brain. Such an effect may be significant for clinical actions of ECT in affective disorders and, possibly, in Parkinson's disease.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

Role of D1 receptor mechanisms in the potentiation of motor responses to L-dopa and apomorphine by MK 801 in the reserpine-treated mouse.

In 24 h reserpine-treated akinetic mice, locomotion was induced by the D1-selective agonist SKF 38393 (30 mg/kg IP), or by the mixed D1/D2 agonists L-dopa (150 mg/kg IP, plus benserazide 100 mg/kg IP) and apomorphine (0.5 mg/kg SC). The non-competitive NMDA receptor antagonist MK 801 (0.01-1.6 mg/kg IP) did not induce motor activity by itself, but potentiated the motor responses to L-dopa and apomorphine at roughly 10-fold lower doses than those which facilitated D1 responding. These data cast doubt on the notion that glutamate antagonists enhance the antiparkinsonian efficacy of mixed D1/D2 agonists solely through a D1 receptor mechanism.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

Motor responses to dopamine D1 and D2 agonists in the reserpine-treated mouse are affected differentially by the NMDA receptor antagonist MK 801.

The akinesia induced by reserpine in mice was effectively reversed by the dopamine D1 receptor agonists SKF 38393 (5-30 mg/kg IP) and CY 208-243 (1-5 mg/kg IP), and by the mixed D1/D2 agonist pergolide (5 mg/kg SC), but less well by the D2 agonists lisuride, PHNO, LY 171555 and RU 24213 (each at 5 mg/kg SC) and not at all by the NMDA receptor antagonist MK 801 (0.1-10 mg/kg IP). MK 801 potentiated D1-dependent locomotion, but always suppressed rearing and grooming. D2-dependent locomotion was inhibited by MK 801. The D2 agonist RU 24213 was antagonised by as little as 6.25 micrograms/kg MK 801, while PHNO and LY 171555 were antagonised by 0.1 mg/kg MK 801. Lisuride was not inhibited by up to 1.6 mg/kg MK 801. Importantly, all animals showed signs of incapacitation with MK 801 in certain elements of their behaviour, most notably ataxia and hind limb abduction. Thus whilst NMDA receptor blockade can facilitate the restoration of movement by dopamine D1 (though not D2) agonists in monoamine-depleted mice, the fluency of the motor response is adversely affected.

Animals↗

Glutamate antagonists modify the motor stimulant actions of D1 and D2 agonists in reserpine-treated mice in complex ways that are not predictive of their interactions with the mixed D1/D2 agonist apomorphine.

In 24h reserpine-treated mice, the locomotion induced by the D1 dopamine agonist SKF 38393 (30 mg/kg IP) was facilitated by the NMDA antagonists MK 801 (0.4 mg/kg IP), CPP (1 mg/kg IP), CGP 40116 (1 mg/kg IP) and HA 966 (2 mg/kg IP), and by the AMPA antagonist NBQX (0.2 mg/kg IP). By contrast, CPP, CGP 40116 and NBQX had no effect on, while MK 801 and HA 966 suppressed, the locomotion elicited by the selective D2 agonist RU 24213 (5 mg/kg SC). When these same doses of glutamate antagonists were tested against the locomotion induced by a threshold (0.025 mg/kg SC), intermediate (0.1 mg/kg SC) or large dose (0.5 mg/kg SC) of the mixed D1/D2 agonist apomorphine, CPP, CGP 40116 and HA 966 were found to have no significant effect, whilst MK 801 was strongly inhibitory and NBQX potentiated the response to 0.1 mg/kg apomorphine only. It is evident from these data that the behavioural interaction profiles between glutamate antagonists and dopamine agonists are complex and depend on the receptor selectivities of the drugs concerned. The manner of the interaction between these glutamate antagonists and selective D1 or D2 agonists, is not predictive of the way that blockade of glutamate transmission interferes with the actions of drugs which have combined D1 and D2 motor stimulant properties.

Animals↗

Autonomic studies in hypertensive patient with unusual sexual dysfunction: response to reserpine.

The authors examined a 48-year-old man with a history of hypertension (6 years) and a history of erection and ejaculation during cold exposure and confrontation with fear (20 years). Exposing the foot to cold water induced ejaculation in 10 seconds. A variety of antihypertensive medications resulted in control of hypertension, without improvement in ejaculatory dysfunction. Similarly, prazosin controlled the blood pressure, but not the episodes of ejaculation. Treatment with reserpine resulted in gradual reduction in blood pressure and an improvement in ejaculatory dysfunction.

Autonomic Nervous System↗

Brainstem genesis of reserpine-induced ponto-geniculo-occipital waves: an electrophysiological and morphological investigation.

Several experimental results indicate that the peribrachial (PB) cholinergic area of the pedunculopontine nucleus is the final relay for the transfer of brainstem-generated pontogeniculo-occipital (PGO) waves to the thalamus. However, the mechanisms underlying the PGO-related activity of PB neurons remain unknown. In order to study these mechanisms, single unit recordings in the PB area were performed in reserpinized cats. Because PGO waves are closely related to rapid eye movements, our microelectrode explorations were also aimed to some structures of the preoculomotor network, namely, the superior colliculus (SC) and parts of the central tegmental field (FTC). We have found several classes of PGO-on cells in the PB area, most of them descharging 80 ms or less before the peak of PGO waves. These cell-classes comprised high-frequency bursting cells, slow-frequency bursting cells, and neurons discharging single spikes or doublets. Intracellular recordings showed that PGO-on single spikes arise from conventional excitatory postsynaptic potentials. Among PGO-related cells in structures outside the PB limits, it was found that most SC cells discharge during or after the PGO, whereas FTC cells increase their discharge rate several hundreds of ms before PGO waves, thus indicating that PGO waves are elaborated long before the activation of PB neurons. Massive retrograde labeling was found in FTC following horseradish peroxidase injections into the PB area. We suggest that long-lead FTC neurons provide an excitatory input to PGO-on PB neurons.

Animals↗

Effects of zinc-aspartate and zinc-glycinate in healthy rats and on reserpine-induced gastric lesions.

Experimental studies performed on 227 rats showed that Zn-aspartate and Zn-glycinate administered ip lowered the incidence, number, and severity of the reserpine-induced gastric lesions ensuring significant protection indices. Histochemical methods revealed increased amount of mucosal glycoproteins. The activity of dehydrogenases involved in energy metabolism that modulates acid secretion in the parietal cells was depressed. RNA content in the chief cells, as premises of pepsinogen synthesis, was decreased. ATPase reaction in the periglandular capillaries was uniform and stronger, showing an improvement of gastric mucosal microcirculation. Since these histochemical changes were also noted in healthy rats receiving Zn salts, it might be suggested that they are not the mere expression of an anti-ulcer protective effect of zinc, but rather reflect its mechanism of action, relating to the complex metabolic events induced by the trace element. Our results are in agreement with those previously reported concerning the noxious influence of Zn depletion, the accelerated healing of peptic ulcer patients after Zn treatment, and the protective effect of Zn against ulcerogenesis in several experimental models involving different pathomechanisms.

Animals↗

Further confirmation of heterogeneity of the rat striatum: different mosaic patterns of dopamine fibers after administration of methamphetamine or reserpine.

Heterogeneity of adult rat neostriatum has been studied by fluorescence histochemistry. The distribution of dopamine nerve fibers and terminals, known normally to be homogeneous, tended to become heterogeneous after administration of methamphetamine or reserpine. Both drugs caused mosaic formations of fluorescent dopamine axons and terminals, though a minor difference was present in the pattern of distribution. The results indicate that the striatum possesses at least two types of dopamine nerve terminals, sensitive and relatively insensitive for the two catecholamine depletors.

Animals↗

Protein kinase C subspecies in hippocampus and striatum of reserpinized rat brain.

Protein kinase C (PKC) (alpha) and (beta) immunoreactivities were determined in the cytosolic and particulate fractions of the hippocampus and striatum after single and repetitive, intraperitoneal administration of reserpine. Significant decrease of PKC(alpha) immunoreactivities was observed in the particulate fractions of both striatum and hippocampus. Compared with the alteration of PKC(alpha), the decreased immunoreactivity of PKC(beta) was only observed in the particulate fraction of the hippocampus, associated with the increase in the cytosolic fraction. These findings suggest a novel mechanism regulating the distribution of PKC. The topographical selectivity in the present study may indicate the importance of the alteration of PKC(beta) in the pathophysiological mechanism in Alzheimer's disease.

Animals↗

Anatomical organization of the phasic activity produced by reserpine at the level of the oculomotor system.

The organization of the pathways responsible for the transmission of phasic electrical activity at the level of the oculomotor system was studied in the encéphale isolé cat which was injected with reserpine or exhibited spontaneous phases of paradoxical sleep. At the level of the VIth nuclei there are both ipsilateral and contralateral connections deriving from each generator. The ipsilateral pathway transmits an "inhibiting" potential eliciting electromyographic inhibition of the ipsilateral rectus muscle, and the contralateral pathway, an "activating" potential eliciting activation of the corresponding lateral rectus muscle. A medial saggital section from frontal plane APO, extending caudally to the VIth nuclei at frontal plan P9 is necessary to suppress the bilateral synchronization of phasic activities recorded from the VIth nuclei and the activation of the lateral rectus muscles. The areas responsible for phasic activity recorded at the level of the central visual and oculomotor systems have been delimited through brain transections. The pathways responsible for the transmission of phasic activity at the level of the IIIrd and IVth nuclei are contiguous with the ponto-geniculate pathways. This was demonstrated by electrocoagulation.

Abducens Nerve↗

Modification of the L-DOPA reversal of reserpine akinesia by inhibitors of dopamine-beta-hydroxylase.

The effect of the dopamine-beta-hydroxylase inhibitors (DBHI) FLA-63 and U10,157 on the reversal of reserpine akinesia by L-DOPA in mice was investigated both behaviourally and by measurement of the cerebral amines dopamine and noradrenaline. Pretreatment of reserpinised animals with intraperitoneal, but not oral, FLA-63 produced hypermotility in the first hour after L-DOPA administration, compared to animals receiving L-DOPA alone. This enhanced activity was associated with an increase in dopamine, but no significant change in the noradrenaline content of whole brain. Pretreatment with both oral and intraperitoneal FLA-63 caused dose-dependent suppression of locomotor activity in the second and third hours after L-DOPA. This suppression was associated with a significant decrease in brain noradrenaline in the presence of a significant elevation in brain dopamine. Pretreatment of animals with U10,157 produced similar but less marked behavioural responses. The results do not appear to be due to stressful effects of DBHI's, causing release of corticosteroids; neither corticosterone nor beta-methasone had any significant effect on L-DOPA-induced locomotor activity in reserpinised animals, although they did increase spontaneous motor activity in normal animals. The data presented support the concept that both noradrenaline and dopamine are responsible for the gross motor activity induced by L-DOPA in the reserpinised mouse.

Adrenal Cortex Hormones↗

Effects of denervation and reserpine on nexuses in the rat vas deferens.

Permanganate-fixed vasa deferentia from rats were examined for the presence of nexal-like contacts by electron microscopy. There was a significantly greater incidence of nexuses (2X) in chronically denervated tissues (5-7 days) but not in tissues from reserpine-pretreated animals (1.0 mg/kg/day for 5-7 days). The results suggest that an increase in nexal regions may not be a general feature of postjunctional supersensitivity but rather may contribute to other denervation-induced changes in contractile response.

Animals↗