Dopamine agonists induce recovery from surgically-induced septal rage

Randomized, placebo-controlled, double-blind study of ropinirole in chronic stroke

BACKGROUND AND PURPOSE

Evidence suggests the potential to improve motor status in patients with stroke by modifying brain catecholaminergic tone. The current study hypothesized that increased dopaminergic tone via the dopamine agonist ropinirole, when combined with physiotherapy (PT), would significantly and safely increase gait velocity.

METHODS

Patients with moderate motor deficits due to stroke 1 to 12 months prior were randomized (double blinded) to 9 weeks of immediate-release ropinirole or placebo, each with PT, and followed up for 3 additional weeks. Drug dose (0.25 to 4 mg once daily) was titrated weekly, as tolerated. The primary end point was gait velocity during the 12 weeks of study participation.

RESULTS

Patients in the ropinirole+PT group averaged 2.4 mg/d by end of week 9, although the target dose was at least 3 mg/d. Ropinirole+PT was generally safe and well tolerated, including no drug-related serious adverse events. Across all 33 enrollees, significant gains were found over time for gait velocity and for most secondary end points. However, gains did not differ by treatment assignment. PT and occupational therapy were commonly prescribed outside of the trial, although the extent of these was not correlated with study outcomes.

CONCLUSIONS

At doses achieved in this trial, increased dopaminergic tone via ropinirole+PT was generally well tolerated but did not show any improvement over and above the effects of PT alone.

Dopamine Presynaptically Depresses Fast Inhibitory Synaptic Transmission via D4 Receptor-Protein Kinase A Pathway in the Rat Dorsolateral Septal Nucleus

The lateral septal nucleus receives a diffuse dopaminergic input originating from the ventral tegmental area of the brain stem. We examined whether dopamine (DA) modulates synaptic transmission in the slice preparation of the rat dorsolateral septal nucleus (DLSN). Bath application (10–15 min) of DA (30 μM) markedly depressed the amplitude of fast and slow inhibitory postsynaptic potentials (IPSPs) in DLSN neurons, while it produced only a minor depression of the amplitude of excitatory postsynaptic potentials (EPSPs) obtained in the presence of bicuculline. DA (30 μM) depressed the monosynaptic fast IPSP to ∼50% of control, but did not depress the inward current ( IGABA) induced by exogenous γ-aminobutyric acid (GABA). DA decreased the frequency of miniature fast IPSPs (m-fIPSPs) without significantly changing their amplitude. PD 168077, a selective D4 receptor agonist, depressed the fast and slow IPSPs but not the EPSP and decreased the frequency of m-fIPSPs. Both DA and PD 168077 increased the paired-pulse ratio of the monosynaptic fast IPSP. The inhibitory effect of DA on the fast IPSP was significantly attenuated by L-741,742, an antagonist at D4 receptors, but not by SCH 23390 and sulpiride, a D1-like and a D2-like receptor antagonist, respectively. N-ethylmaleimide, a blocker of pertussis toxin (PTX)-sensitive G protein ( Gi/o), attenuated the DA-induced depression of the fast IPSP. N-[2-((p-bromocinnamyl) amino)ethyl]-5-isoquinoline sulfonamide, a protein kinase A (PKA) inhibitor, attenuated the DA-induced depression of the fast IPSP. These results suggest that DA inhibits spontaneous and evoked release of GABA via the D4 receptor- Gi-protein-PKA system in DLSN neurons.

Drug treatments of dementia

Present drug treatments for the more common types of dementia are largely palliative or symptomatic, but the promise of drugs to prevent the development of dementia does not seem unrealistic. Neuropharmacological strategies that aim to improve behavioural or cognitive symptoms in dementia are subdivided into drugs that modify central cholinergic, serotonergic, dopaminergic, GABAnergic, and peptidergic transmission. There are no clear clinical guidelines for the management of demented patients who are also hypertensive. The early identification of patients with incipient dementia, the detection of slight but theoretically important beneficial effects, the optimum method of drug administration, more soundly based treatment of behavioural symptoms, and the evaluation of drug combinations are all identified as areas requiring further research.

Amantadine for the agitated head-injury patient

Traumatic brain injury may be associated with agitated aggressive behaviour and the potential for injury to the patient and staff. We report two cases of recovering brain injury patients with difficult-to-treat destructive behaviour, whose agitation and aggression responded to amantadine. Direct-acting dopamine agonists such as amantadine may be the preferred treatment for patients with behaviour problems in the acute stages of recovery from coma.

Pharmacotherapy and the neurobehavioural sequelae of traumatic brain injury

Recent advances in clinical neuropharmacology are likely to improve the treatment and rehabilitation of traumatic brain injury (TBI) patients. Treatment may be directed to alleviate specific symptoms, to improve function in certain areas, or even to enhance the cortical recovery process. The author reviews pertinent issues in clinical neuropharmacology for the following drug classes: stimulants, other dopamine agonists, antidepressants, lithium, cholinergics, neuroleptics, anticonvulsants, beta-blockers, calcium channel blockers, nootropes, opiates and neuropeptides. Since the relevant research literature in TBI is so sparse, information and recommendations are extrapolated from some other patient groups, especially developmentally handicapped children and adults, and patients with dementia.

Evidence that amphetamine with physical therapy promotes recovery of motor function in stroke patients

We conducted a double-blind pilot study of 8 patients with established cerebral infarction to evaluate the effect of a single dose of amphetamine on recovery of motor function using the Fugl-Meyer scale. Four patients received amphetamine; the rest were given placebo. All underwent a session of physical therapy. Patients treated with amphetamine obtained greater increments in motor scores than the controls. Along with animal studies, these findings may allow the development of a pharmacological approach to stroke rehabilitation.

Recovery of tactile placing after visual cortex ablation in cat: a behavioral and metabolic study of diaschisis

After bilateral visual cortex ablation, cats show a transient deficit in tactile placing and a permanent deficit in visual placing of both forelimbs. Amphetamine administration (four doses, 5 mg/kg, i.p., spaced at 4-day intervals beginning 10 days after surgery) accelerated the rate of recovery of tactile placing compared with saline controls whereas visual placing was not affected. The catecholamine antagonist, haloperidol (0.4 mg/kg, i.p.), blocked the amphetamine-enhanced recovery of tactile placing. Additionally, the visual cortex lesions produced a depression of oxidative metabolism, measured by cytochrome oxidase histochemistry, in subcortical regions remote from the injury. Animals treated with amphetamine exhibited an alleviation of this metabolic depression in the superior colliculus but not in other regions.

Inter-male aggressive signals in weakly electric fish are modulated by monoamines

Apteronotus leptorhynchus is a gymnotid fish producing a constant high frequency electric organ discharge (EOD). Males of this species use transient increases in EOD frequency (chirps) as aggressive signals. They will also shift the frequency of their EOD away from the similar frequency of a nearby conspecific in order to protect their ability to electrolocate (jamming avoidance response, JAR). Monoamines have been implicated as modulatory agents for various sensorimotor and affective systems, including aggressive behaviour. Since these monoamines are present in the brain of this fish (unpublished observation), we have used these simple and quantifiable behaviours to study the role of monoamines, with special emphasis on possible specific effects on aggressive signalling (chirps). When serotonin (0.1 microgram) is injected directly into the ventricle of these fish it briefly inhibits chirping (aggression) without inhibiting the JAR; this is consistent with the hypothesis that, in mammals, serotonin inhibits aggressive behaviour. Noradrenaline (0.1 microgram) enhances both chirping and the JAR. Dopamine (0.1 microgram) enhances the JAR; it has powerful but inconsistent effects on chirping (inhibition or excitation).

Activation, arousal, and neuropsychological rehabilitation

This paper addresses the concept of arousal and the role of the reticular system in producing the orienting response. For patients with deviant autonomic responses, the use of central neuropharmacological stimulants is considered. Their therapeutic value is discussed in relation to hyperactive children and individual adult cases of the posttraumatic syndrome consequent upon traffic accidents.

Dopamine agonists produce functional recovery from septal lesions which affect hypothalamic defensive attack in cats

Effects of lesions of the lateral septum and subsequent administration of methamphetamine (MAT, 1 mg/kg, i.p.) or apomorphine (APO, 1 mg/kg, i.p.) on thresholds for defensive attack elicited by electrical stimulation of the ventromedial hypothalamic nucleus (VM) were examined. Hissing and directed attack were selected for threshold determination. Thresholds were measured under two situations: one with provocation by a human and the other without it. Electrolytic lesions of the lateral septum enhanced the facilitative influences exerted by the provocation on the thresholds, however, subsequent administration of MAT or APO abolished or tended to abolish the enhancement. The rapid recovery of function was interpreted to have taken place due to excessive dopaminergic inputs to the spared tissue of the lateral septum, and a gating mechanism of neuronal information by dopamine was suggested.

Cerebral decortication reverses the effect of amphetamine on striatal D2 dopamine binding site density

Unilateral ablation of the cerebral cortex produces a decrease of approximately 38% in striatal D2 dopamine binding site density. Chronic d-amphetamine treatment also produces a decrease of about 22% in D2 binding site density. Paradoxically, when rats were hemidecorticated and treated chronically with d-amphetamine, the density of striatal D2 dopamine binding sites on the decorticated side was increased (by about 50%) rather than decreased. Evidently d-amphetamine-induced down-regulation of D2 dopamine binding sites depends on an intact corticostriatal pathway.

Recovery of function after brain damage: severe and chronic disruption by diazepam

Following unilateral damage to the anterior-medial region of the neocortex (AMC) in rats a sensory asymmetry appeared, but recovered within a week. In a separate group of rats with AMC lesions daily 3-week exposure to diazepam (Valium, 5 mg/kg) beginning 12 h after surgery caused recovery to be delayed indefinitely. The efficiency and speed (as opposed to symmetry) of behavior was not impaired. More than 9 weeks after discontinuation of diazepam (12 weeks postsurgery), recovery was still not apparent. Postmortem analysis ruled out lesion size as a contributing factor. In a second experiment undrugged animals with AMC lesions were allowed to recover for at least 3 weeks before being exposed to diazepam. These animals showed only a transient (2-day) reinstatement of asymmetry despite continuous drug treatment. We conclude that important mechanisms serving recovery of function may be vulnerable during a short period soon after brain damage.

Dopaminergic facilitation of recovery from amygdaloid lesions which affect hypothalamic defensive attack in cats

Influence of dopamine agonists, methamphetamine (MAT, 1 mg/kg, i.p.) and apomorphine (APO, 1 mg/kg, i.p.), on the effects of amygdaloid lesions on thresholds for the defensive attack behavior elicited by electrical stimulation of the ventromedial hypothalamic nucleus was studied in cats. The thresholds were measured in two situations, one with provocation by a human and the other without provocation. Electrolytic lesions of the basolateral part of the amygdala attenuated markedly facilitatory influences of the visual provocation on the thresholds, but subsequent administration of MAT or APO rapidly abolished the effects of the lesions. The effects of MAT lasted for at least 3.5 h while the effects of APO were of shorter duration. The results were discussed from the viewpoint of possible rapid compensation by the remaining intact tissue of the amygdala which was produced by excessive dopaminergic inputs to it.

Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation

In adult cats with bilateral visual cortex ablation the complete deficit in binocular depth perception, as measured on a visual cliff, was reversed by 4 doses of amphetamine. The amphetamine-induced recovery endured after the amphetamine treatment was discontinued. This enduring recovery of function was not obtained if the animals were housed in the dark during drug intoxication. Therefore, both amphetamine intoxication and visual experience are simultaneously required for recovery of binocular depth perception after visual cortex ablation.

An ACTH4-9 analog (ORG 2766) speeds recovery from septal hyperemotionality in the rat

The amount of hyperemotionality initially demonstrated after septal area lesions was reduced, and the rate at which the hyperemotionality attenuated over repeated testing, was enhanced by the administration of an ACTH4-9 analog, ORG 2766. This ACTH fragment was given for 4 consecutive days after surgery but terminated before testing began. Two weeks after the daily tests of emotionality, the animals were trained in a two-way active avoidance task. The typical increase in avoidance behavior seen in animals with septal lesions was observed in the lesioned animals tested with ORG 2766, but the usual high number of intertrial responses was greatly reduced in these animals. The results indicate that even after a brief series of ORG 2766 administration, there are changes in emotionality that may last for an extended period of time after the cessation of treatment.

Amphetamine, haloperidol, and experience interact to affect rate of recovery after motor cortex injury

Rats subjected to unilateral ablation of the motor cortex and placed on a narrow beam displayed transient contralateral paresis. An immediate and enduring acceleration of recovery was produced by a single dose of d-amphetamine given 24 hours after injury. This effect was blocked by haloperidol or by restraining the animals for 8 hours beginning immediately after amphetamine administration. A single dose of haloperidol given 24 hours after injury markedly slowed recovery. This effect was also blocked by restraining the animals.

Biochemical specificity of septal hyperreactivity: a behavioral discrimination

Intra-septal injections of specific monoamine and cell body neurotoxins were used to determine the anatomical and biochemical elements critical to both short and longer term changes in reactivity normally seen after septal lesions. A multivariate discrimination performed on the basis of tactile, foot-shock and heat responsiveness revealed that septal lesions have a unique effect not accounted for by specific monoamine induced degeneration. Injections of 6-hydroxydopa and monosodium glutamate had slight effects on heat and shock responsiveness not at all comparable in degree or kind to septal lesion effects. Decreased hippocampal, but not hypothalamic, levels of norepinephrine may be associated with the longer term increased responsiveness to shock and heat in animals with septal lesions.

The influence of dopamine on active sodium transport across frog skin measured as short circuit current

The influence of dopamine (DA) on short circuit current (SCC) across isolated Rana esculenta skin was studied to determine whethera a DA receptor system exists in that cell membrane model and what is the influence of DA on SCC. Experiments were carried out with both alpha- and beta-adrenergic blockers and cocaine present in the Ringer solution. DA in cumulative doses added to the inner Ringer solution stimulated SCC in a dose-dependent manner. Apomorphine (10(-5) M) shifted the DA dose--response curve to the left and increased the maximum DA response. Haloperidol (10(-9) M) antagonized the effects of the DA depressing maximum response as well. Imidazole (10(-8) M and 10(-9) M) antagonized the influence of DA in a manner similar to haloperidol. It appeared that there were DA receptors in frog skin and that haloperidol as well as imidazole were DA antagonists which acted non-competitively.

Endogenous norepinephrine and serotonin within the hippocampal formation during the development and recovery from septal hyperreactivity

Fluorometric analysis of serotonin (5-HT) and norepinephrine (NE) content of the hippocampal formation revealed that biogenic amines are distributed heterogeneously in the dorsoventral axis, and that NE also exhibits a heterogeneous distribution in the medial-lateral direction while 5-HT does not. Dissection of the hippocampus into its dorsal and ventral halves shows that both NE and 5-HT exhibit higher concentrations in the ventral hippocampus in comparison to its dorsal counterpart. A dissection which separated the cell fields CA 1 and 2 from CA 3 and 4 and the dentate gyrus showed NE to be the highest in the latter region, while 5-HT was uniformly distributed between the two regions. Taken together, these data indicate that NE is more highly concentrated in the CA 3 and 4 and dentate area of the ventral hippocampus while 5-HT concentration differences are apparent only in a dorsal-ventral dissection. Concentrations of NE and 5-HT in the dorsal and ventral hippocampus were also determined at 1, 3, 6, 11, 16, 24, and 30 days following a lesion to the septal nuclei. The results demonstrate that biogenic amine levels in the dorsal hippocampus achieve maximal depletion earlier than do their ventral counterparts, and that percent depletion is greater for 5-HT than NE in both dorsal and ventral areas. On the first day following septal lesions, 5-HT is increased above normal levels. Sixteen days after septal lesion, 5-HT is substantially depleted below normal levels. In addition, by 30 days, 5-HT shows significant return toward normal levels from its earlier depleted state. Behavioral changes related to sensory reactivity correlate with the relative decreases of NE and 5-HT following septal lesions.