Baclofen-impairment of memory retention in rats: possible interaction with adrenoceptor mechanism(s)

Long-term results on the suppression of secondary brain injury by early administered low-dose baclofen in a traumatic brain injury mouse model

Secondary injury from traumatic brain injury (TBI) perpetuates cerebral damages through varied ways. Attenuating neuroinflammation, which is a key feature of TBI, is important for long-term prognosis of its patients. Baclofen, a muscle relaxant, has shown promise in reducing excessive inflammation in other neurologic disorders. However, its effectiveness in TBI remains ambiguous. Thus, our study aimed to investigate whether early administration of baclofen could elicit potential therapeutic effects by diminishing exaggerated neuroinflammation in TBI mice. In this study, 80 C57BL/6 mice were used, of which 69 mice received controlled cortical impact. The mice were divided into six groups (11-16 mice each). Baclofen, administered at dose of 0.05, 0.2 and 1 mg/kg, was injected intraperitoneally a day after TBI for 3 consecutive weeks. 3 weeks after completing the treatments, the mice were assessed histologically. The results showed that mice treated with baclofen exhibited a significantly lower volume of lesion tissue than TBI mice with normal saline. Baclofen also reduced activated glial cells with neurotoxic immune molecules and inhibited apoptotic cells. Significant recovery was observed and sustained for 6 weeks at the 0.2 mg/kg dose in the modified neurological severity score. Furthermore, memory impairment was recovered with low-doses of baclofen in the Y-maze. Our findings demonstrate that early administration of low dose baclofen can regulate neuroinflammation, prevent cell death, and improve TBI motor and cognitive abnormalities.

Systemic and intrathecal baclofen produce bladder antinociception in rats

BACKGROUND

Baclofen, a clinically available GABAB receptor agonist, produces non-opioid analgesia in multiple models of pain but has not been tested for effects on bladder nociception.

METHODS

A series of experiments examined the effects of systemic and spinally administered baclofen on bladder nociception in female anesthetized rats. Models of bladder nociception included those which employed neonatal and adult bladder inflammation to produce bladder hypersensitivity.

RESULTS

Cumulative intraperitoneal dosing (1-8 mg/kg IP) and cumulative intrathecal dosing (10-160 ng IT) of baclofen led to dose-dependent inhibition of visceromotor responses (VMRs) to urinary bladder distension (UBD) in all tested models. There were no differences in the magnitude of the analgesic effects of baclofen as a function of inflammation versus no inflammation treatments. Hemodynamic (pressor) responses to UBD were similarly inhibited by IT baclofen as well as UBD-evoked excitatory responses of spinal dorsal horn neurons. The GABAB receptor antagonist, CGP 35,348, antagonized the antinociceptive effects of IT baclofen on VMRs in all tested models but did not affect the magnitude of the VMRs by itself suggesting no tonic GABAB activity was present in this preparation. Tolerance to a seven day continuous IT infusion of baclofen was not observed.

CONCLUSIONS

These data provide support for a clinical trial of baclofen as a non-opioid treatment of human bladder pain.

Improvement of Memory Functions in Chronic Spinal Cord Injury After Long-Term Intrathecal Baclofen Delivery for Spasticity Relief

BACKGROUND

Intrathecal baclofen (ITB) pump delivery systems are safe and effective in the treatment of generalized spasticity in chronic spinal cord injury (SCI). Despite its widespread use, few and discrepant data are available in animal studies on the effects of ITB on cognitive functions, such as memory. The effects of chronic administration of baclofen on humans have not been investigated to date. The aim of this study is to find out, whether a long-term administration of ITB has any effects on cognitive functions in SCI subjects.

MATERIALS AND METHODS

In 11 out of 22 subjects with chronic SCI, we performed comprehensive neuropsychological assessment carried out using specialized tests focused on memory and other higher cognitive domains and emotional state.

RESULTS

All patients receiving ITB treatment for spasticity relief improved significantly in RAVLT Trials 1-5 (p = 0.049), Logical memory-immediate recall (p = 0.019) and Logical memory-delayed recall (p = 0.008). Visual memory, long-term semantic memory, attention, executive, perceptual and spatial functions, and mood status remained stable.

CONCLUSION

No significant decline in memory functions were detected following one year of ITB delivery, creating an opportunity for careful prescription of this treatment in chronic SCI. Moreover, we have detected a significant increase in short-term auditory-verbal memory and logical memory performance.

Cognitive Dysfunction in Persons with Chronic Spinal Cord Injuries

Cognitive dysfunction (CD) is pervasive in individuals who have chronic spinal cord injuries (SCI). Although classically associated with concomitant traumatic brain injuries, many other causes have been proposed, including premorbid neuropsychological conditions, mood disorders, substance abuse, polypharmacy, chronic pain and fatigue, sleep apnea, autonomic dysregulation, post-intensive care unit syndrome, cortical reorganizations, and neuroinflammation. The consequences of CD are likely widespread, affecting rehabilitation and function. CD in those with SCI should be recognized, and potentially treated, in order to provide the best patient care.

Comparative effects of chronic administrations of gabapentin, pregabalin and baclofen on rat memory using object recognition test

Memory impairment is one of the greatest concerns when it comes to long-term CNS-affecting drug administration. Drugs like gabapentin, pregabalin and baclofen are administered in a long-term period in conditions such as epilepsy, neuropathic pain, spasticity associated with spinal cord injury or multiple sclerosis. Despite their wide spread use, few data are available on the effects of these drugs on cognitive functions, such as learning memory. In the present study, the effects of long-term administration of gabapentin, pregabalin and baclofen on memory were investigated in a comparative manner. Male Wistar rats received intraperitoneal (i.p.) injection of gabapentin (30 mg/kg), pregabalin (30 mg/kg), baclofen (3 mg/kg), combination of gabapentin/baclofen (30/3 mg/kg) and combination of pregabalin/baclofen (30/3 mg/kg) once a day for 3 weeks respective to their groups. After the end of treatments, rat memories were assessed using the object-recognition task. The discrimination and recognition indices (RI and DI) in the T2 trials were used as the memory indicating factors. The results showed that daily i.p. administrations of pregabalin but not gabapentin or baclofen significantly decreased DI and RI compared to saline group. In combination groups, either gabapentin or pregabalin impaired discrimination between new and familiar objects. Our findings suggested that pregabalin alone or in combination with baclofen significantly caused cognitive deficits.

Influence of intrathecal baclofen on the level of consciousness and mental functions after extremely severe traumatic brain injury: brief report

BACKGROUND

Whenever oral treatment or botulinum toxin injections fail to control severe spasticity, a trial with intrathecal baclofen is recommended no earlier than 1 year after brain injury. When irreversible contractures are to be avoided, such a trial might be done earlier. Some have briefly reported cognitive modifications with this treatment.

METHODS

During the trial period, intrathecal baclofen is continuously infused by a portable external pump through an intrathecal catheter. The daily dose is adjusted according to the clinical response. If the expected response is obtained by reduction of spasticity, a programmable pump is then implanted. Throughout the procedure, close neuropsychological follow-up is pursued.

RESULTS

Two persons with extremely severe brain injury and spasticity received a programmable pump less than 10 months after trauma. Unexpectedly, one emerged from the minimally conscious state and the other from post-traumatic amnesia.

CONCLUSIONS

Intrathecal baclofen should be considered within the first year after brain injury whenever spasticity does not respond to medication. ITB lessens the degree of spasticity which in turn facilitates care and, thus, has the potential to limit contractures. After severe brain injury, this treatment might trigger recovery from altered states of consciousness, improve cognition and facilitate rehabilitation.

Baclofen alters gustatory discrimination capabilities and induces a conditioned taste aversion (CTA)

Background

Studies intending to measure drug-induced changes in learning and memory are challenged to parse out the effects of drugs on sensory, motor, and associative systems in the brain. In the context of conditioned taste aversion (CTA), drugs that alter the sensorium of subjects and affect their ability to taste and/or feel malaise may limit the ability of investigators to make conclusions about associative effects of these substances. Since the GABAergic system is implicated in inhibition, the authors were hopeful to use the GABA agonist, baclofen (BAC), to enhance extinction of a CTA, but first a preliminary evaluation of BAC's peripheral effects on animals' sensorium had to be completed due to a lack of published literature in this area.

Findings

Our first experiment aimed to evaluate the extent to which the GABA_B agonist, BAC, altered the ability of rats to differentiate between 0.3% and 0.6% saccharin (SAC) in a two bottle preference test. Here we report that 2 or 3 mg/kg (i.p.) BAC, but not 1 mg/kg BAC, impaired animals' gustatory discrimination abilities in this task. Furthermore, when SAC consumption was preceded by 2 or 3 mg/kg (i.p.) BAC, rats depressed their subsequent SAC drinking.

A second experiment evaluated if the suppression of SAC and water drinking (revealed in Experiment 1) was mediated by amnesiac effects of BAC or whether BAC possessed US properties in the context of the CTA paradigm. The time necessary to reach an asymptotic level of CTA extinction was not significantly different in those animals that received the 3 mg/kg dose of BAC compared to more conventionally SAC + lithium chloride (LiCl, 81 mg/kg) conditioned animals.

Conclusions

Our findings were not consistent with a simple amnesia-of-neophobia explanation. Instead, results indicated that 2 and 3 mg/kg (i.p.) BAC were capable of inducing a CTA, which was extinguishable via repeated presentations of SAC only. Our data indicate that, depending on the dose, BAC can alter SAC taste discrimination and act as a potent US in the context of a CTA paradigm.

Effects of asiatic acid on passive and active avoidance task in male Spraque-Dawley rats

AIM OF THE STUDY

Centella asiatica has a reputation to restore declining cognitive function in traditional medicine. To date, only a few compounds that show enhancing learning and memory properties are available. Therefore, the present study investigates the effects of for acute administration of asiatic acid (A-A) isolated from Centella asiatica administration on memory and learning in male Spraque-Dawley rats.

MATERIALS AND METHODS

4-5 weeks Spraque-Dawley rats were administered with concentration 1, 3, 5, 10, 30 mg/kg of A-A, baclofen, scopolamine and saline intra peritoneally and were evaluated for passive avoidance (PA), active avoidance (AA) and changes in blood pressure (BP).

RESULTS

Treatment 30 mg/kg of A-A resulted in significantly dose-dependently improved memory, with increased retention latency to enter difference compartment in PA test compared to baclofen, saline and scopolamine. Furthermore, 30 mg/kg of A-A was significantly higher on learning abilities on 1st day but there was no significantly difference on avoidance memory ability after 7 days of retention. Low reading in blood pressure dose-dependent significantly difference was observed in the 30 mg/kg of A-A group compared to saline group.

CONCLUSIONS

Administration A-A facilitated PA and AA on memory and learning and but had no effect on active avoidance on memory. Hence, may serve useful memory and learning with less effect in blood pressure in promoting memory and learning increases.

Relationship between intrathecal baclofen and the central nervous system

The GABA(B) receptor agonists display a number of pharmacological effects including central muscle relaxation, decreased self-administration of cocaine and narcotic drugs, antinociception, cognitive impairment as well as enhancement of synaptic plasticity. The main relationships between intrathecal or intracerebral baclofen and the Central Nervous System (CNS) are reviewed with particular attention to actions on pain, epilepsy and basal ganglia regulation. Since baclofen may be involved in synaptic plasticity and the development of neuronal pathways, the main issues of this field are reviewed with particular attention to the effects of baclofen on the developing brain. The role of baclofen in the regulation of movement has not been clearly understood, but recent findings support its important involvement in globus pallidus and subthalamic nucleus. The neuroprotective action of baclofen in cerebral ischemia is a matter of debate. The effects of baclofen in cognition and attention are another important issue because patients with chronic intrathecal baclofen (ITB) administration often present with impairment of cognitive functions. Drug craving and its improvement after baclofen administration is also reviewed. Finally, the clinically interesting results on the regulation of food intake and blood pressure are highlighted. The preliminary experience on the effects in cortical neuron viability at different concentrations of ITB is reported.

Baclofen interactions with nicotine in rats: effects on memory

Nicotine has been shown in numerous previous studies to significantly improve memory on the radial-arm maze, yet the critical mechanisms underlying this effect are not fully characterized. Nicotine stimulates the release of a number of neurotransmitters important for memory function including (gamma-aminobutyric acid) GABA. The importance of nicotinic-GABA interactions regarding memory is currently unknown. The purpose of the current study was to determine the interactive effects of nicotine and the GABA agonist baclofen on working memory function as measured by choice accuracy in the radial-arm maze. Female Sprague-Dawley rats trained to asymptotic performance levels on a win-shift eight-arm radial maze task were used for assessment of nicotine-baclofen interactions. Low doses of baclofen improved memory performance while higher doses impaired it. Nicotine, as seen before, improved memory performance. Nicotine also significantly reversed the higher dose baclofen-induced deficit. These data show the importance of both nicotinic and GABA systems in working memory function and the interactions between these two transmitter receptor systems. This not only provides information concerning the neural bases of cognitive performance, it also lends insight into new combination treatments for memory impairment.

Influence of β-adrenoceptor agonists and antagonists on baclofen-induced memory impairment in mice

Post-training administration of different doses of baclofen (a GABAB agonist) has been shown to impair memory retention, in a step-down passive avoidance test in mice. We have studied the effects of beta-adrenergic agonists and antagonists on baclofen-induced memory impairment in mice. Dobutamine (a beta 1-agonist) or salbutamol (a beta 2-agonist) reversed the memory impairment induced by baclofen without exhibiting intrinsic actions on memory when administered alone. The administration of atenolol (a beta 1-antagonist) or propranolol (a beta-antagonist) produced a memory impairment. When co-administered with baclofen, both atenolol and propranolol exacerbated the memory impairment induced by the GABAB agonist. It is concluded that beta-adrenergic mechanisms may be involved in the modulation of memory via GABAB receptors.