Seizures produced by pilocarpine in mice: A behavioral, electroencephalographic and morphological analysis

Increasing doses of pilocarpine, 100-400 mg/kg, were given intraperitoneally to mice and the resulting behavioral, electroencephalographic and neuropathological alterations were studied. No behavioral phenomena were observed in mice treated with the lowest dose of pilocarpine. Occasional tremor and myoclonus of hindlimbs were found in animals which received pilocarpine in a dose of 200 mg/kg. At doses of 300, 325 and 350 mg/kg, pilocarpine produced a sequence of behavioral alterations including staring spells, limbic gustatory automatisms and motor limbic seizures that developed over 15-30 min and built up progressively into a limbic status epilepticus lasting for several hours. The highest dose of pilocarpine, 400 mg/kg, was generally lethal to mice. Pilocarpine produced both interictal and ictal epileptiform activity in the electroencephalogram (EEG). The earliest EEG alterations appeared in the hippocampus and then spread to cortical areas. EEG seizures started 10-15 min after injection of large doses of pilocarpine, 300-350 mg/kg. Ictal periods lasted for 1-2 min, recurred every 5-10 min and were followed by periods of depression of the EEG activity. By 30-45 min paroxysmal activity resulted in a status epilepticus. Examination of frontal forebrain sections with light microscopy revealed a widespread damage to several brain regions including the hippocampus, amygdala, thalamus, olfactory cortex, neocortex and substantia nigra. Scopolamine, 10 mg/kg, and diazepam, 10 mg/kg, prevented the development of convulsive activity and brain damage produced by pilocarpine. The results emphasize that excessive and sustained stimulation of cholinergic receptors can lead to seizures and seizure-related brain damage in mice. It is proposed that systemic pilocarpine in mice provides a useful animal model for studying mechanisms of and therapeutic approaches to temporal lobe epilepsy.     

Headaches as the main presenting symptom of subacute angle closure glaucoma

The diagnosis of subacute angle closure glaucoma is suspected in patients with narrow angles of the anterior chamber of the eye, presenting with periodic ocular, or periocular pain. However, some patients may present with headaches in the absence of significant ocular discomfort, which often leads to misdiagnosis and delay in specific therapy. The clinical features of 9 such patients are described. Subacute angle closure glaucoma should always be considered in the differential diagnosis of adult-onset headaches.     

Congenital Mydriasis: Diagnostic Challenge in a Case with Accompanying Neurologic Symptoms

A 34-year-old woman was hospitalised with acute onset nausea, vomiting, ataxia, nystagmus, blurred vision, and bilateral mydriasis. Toxicologic investigations and serologic tests for infectious aetiologies were negative. Demyelinating disease was suspected based on magnetic resonance imaging (MRI) findings but there were no lesions at the midbrain explaining bilateral mydriasis. Direct light, consensual light, and near responses for pupil were all negative. Biomicroscopic examination of the iris did not show any sphincter damage or tonic movements. Pupils didn’t respond to pilocarpine (0.1% and 2%) and remained unresponsive during the follow-up period. Congenital mydriasis was diagnosed because old photographs revealed that pupils were dilated previously.     

Skin pretreatment with microneedles prior to pilocarpine iontophoresis increases sweat production

Collection of sweat via pilocarpine iontophoresis is commonly used to diagnose cystic fibrosis (CF), with thousands of tests performed each day. The main source of resistance to the passage of pilocarpine ions to the sweat glands is the electrical resistance of the stratum corneum. It was hypothesized that pretreating the skin with 0·5 mm‐long microneedles would significantly decrease this resistance, thus increasing pilocarpine's permeation into the skin. Improved permeation should result in significantly reduced time to sweat initiation, time to collection of a clinically meaningful amount of sweat, and increased total amount of sweat produced in 15 min. Subjects (n = 12) had two 5 cm² areas on the forearm measured, marked and randomized to experimental (microneedles + iontophoresis) or control (iontophoresis alone). Microneedle pretreatment was conducted using a 35‐needle microneedle stamp in a manner that 20 applications completely covered the 5 cm² treatment area. This was repeated five times for a total of 100 applications. Both experimental and control sites were placed under iontophoresis (1·5 mA) for 5 min. Microneedle pretreatment significantly decreased mean skin resistance (260 ± 27 kΩ versus 160 ± 19 kΩ, P = 0·006), while significantly increasing mean sweat rate (0·76 ± 0·35 versus 0·54 ± 0·19 μl cm² min^?1, P = 0·007). No significant difference was found concerning pain (P = 0·059), number of active sweat glands (P = 0·627) or the osmolality of the collected sweat (P = 0·636). The results of this study suggest that microneedle pretreatment prior to pilocarpine iontophoresis significantly increases sweat production. Such results have the potential to improve the methodology currently used to diagnose cystic fibrosis and, more broadly, to administer drugs via the skin.     

Morphometry of hilar ectopic granule cells in the rat

Granule cell (GC) neurogenesis in the dentate gyrus (DG) does not always proceed normally. After severe seizures (e.g., status epilepticus [SE]) and some other conditions, newborn GCs appear in the hilus. Hilar ectopic GCs (EGCs) can potentially provide insight into the effects of abnormal location and seizures on GC development. Additionally, hilar EGCs that develop after SE may contribute to epileptogenesis and cognitive impairments that follow SE. Thus, it is critical to understand how EGCs differ from normal GCs. Relatively little morphometric information is available on EGCs, especially those restricted to the hilus. This study quantitatively analyzed the structural morphology of hilar EGCs from adult male rats several months after pilocarpine-induced SE, when they are considered to have chronic epilepsy. Hilar EGCs were physiologically identified in slices, intracellularly labeled, processed for light microscopic reconstruction, and compared to GC layer GCs, from both the same post-SE tissue and the NeuroMorpho database (normal GCs). Consistently, hilar EGC and GC layer GCs had similar dendritic lengths and field sizes, and identifiable apical dendrites. However, hilar EGC dendrites were topologically more complex, with more branch points and tortuous dendritic paths. Three-dimensional analysis revealed that, remarkably, hilar EGC dendrites often extended along the longitudinal DG axis, suggesting increased capacity for septotemporal integration. Axonal reconstruction demonstrated that hilar EGCs contributed to mossy fiber sprouting. This combination of preserved and aberrant morphological features, potentially supporting convergent afferent input to EGCs and broad, divergent efferent output, could help explain why the hilar EGC population could impair DG function.     

Inflammation triggers constitutive activity and agonist-induced negative responses at M(3) muscarinic receptor in dental pulp

The purpose of this study was to investigate whether the inflammation of rat dental pulp induces the muscarinic acetylcholine receptor (mAChR) constitutive receptor activity. Pulpitis was induced with bacterial lipolysaccharide in rat incisors dental pulp. Saturation assay with [³H]-quinuclidinyl benzilate ([³H] QNB), competitive binding with different mAChR antagonist subtypes, and nitric oxide synthase (NOS) activity were performed. A drastic change in expression and response to mAChR subtypes was observed in pulpitis. Inflamed pulp expressed high number of M₃ mAChR of high affinity, whereas the M₁ mAChR is the main subtype displayed in normal pulp. Consistent with the identification of the affinity constant (Ki) of M₃ and Ki of M₁ in both pulpitis and in normal pulps are the differences in the subtype functionality of these cells. In pulpitis, pilocarpine (1 × 10⁻¹¹ mol/L to 5 × 10⁻⁹ mol/L) exerted an inhibitory action on NOS activity that was blocked by J 104129 fumarate (highest selective affinity to M₃ mAChR). In normal pulps, pilocarpine (1 × 10⁻¹¹ mol/L to 5 × 10⁻⁹ mol/L) has no effect. NOS basal activity was 5.9 times as high in pulpitis as in the normal pulp as a result of the activation of inducible NOS. The irreversible pulpitis could induce a mAChR alteration, increasing the high-affinity receptor density and transduction-coupling efficiency of inducible NOS activity, leading to a spontaneously active conformation of the receptor. Pilocarpine acting as an inverse agonist might be useful therapeutically to prevent necrosis and subsequent loss of dental pulp.     

Changes in glucose metabolism and metabolites during the epileptogenic process in the lithium-pilocarpine model of epilepsy

Purpose: The metabolic and biochemical changes that occur during epileptogenesis remain to be determined. ¹⁸F‐Fluorodeoxyglucose positron emission tomography (FDG‐PET) and proton magnetic resonance spectroscopy (¹H MRS) are noninvasive techniques that provide indirect information on ongoing pathologic changes. We, therefore, utilized these methods to assess changes in glucose metabolism and metabolites in the rat lithium‐pilocarpine model of epilepsy as markers of epileptogenesis from baseline to chronic spontaneous recurrent seizures (SRS). Methods: PET and MRS were performed at baseline, and during the acute, subacute, silent, and chronic periods after lithium‐pilocarpine induced status epilepticus (SE). Sequential changes in glucose metabolism on ¹⁸F‐FDG PET using SPM2 and the ratios of percent injected dose per gram (%ID)/g of regions of interest (ROIs) in the bilateral amygdala, hippocampus, basal ganglia with the thalamus, cortex, and hypothalamus normalized to the pons were determined. Voxels of interest (VOIs) on ¹H MRS were obtained at the right hippocampus and the basal ganglia. NAA/Cr levels and Cho/Cr at various time points were compared to baseline values. Key Findings: Of 81 male Sprague‐Dawley rats, 30 progressed to SRS. ¹⁸F‐FDG PET showed widespread global hypometabolism during the acute period, returning to baseline level during the subacute period. Glucose metabolism, however, declined in part of the hippocampus during the silent period, with the hypometabolic area progressively expanding to the entire limbic area during the chronic period. ¹H MRS showed that the NAA/Cr levels in the hippocampus and basal ganglia were reduced during the acute period and were not restored subsequently from the subacute to the chronic period without any significant change in the Cho/Cr ratio throughout the entire experiment. Significance: Serial metabolic and biochemical changes in the lithium‐pilocarpine model of epilepsy indirectly represent the process of human epileptogenesis. Following initial irreversible neural damage by SE, global glucose metabolism transiently recovered during the subacute period without neuronal recovery. Progressive glucose hypometabolism in the limbic area during the silent and chronic periods may reflect the important role of the hippocampus in the formation of ongoing epileptic network during epileptogenesis.     

匹鲁卡品对Wistar大鼠心律失常的影响

目的观察匹罗卡品对Wistar大鼠心律失常的作用。方法分别以乌头碱、氯化钡制作Wistar大鼠心律失常模型,观察0.2 mg.kg-1匹罗卡品舌下静脉注射对心律失常的作用。结果匹罗卡品可明显延迟乌头碱引起Wistar大鼠室性心律失常的出现(P<0.05)、延长其出现心律失常后的存活时间(P<0.05);匹罗卡品能明显延迟氯化钡引起Wistar大鼠双相室性心律失常的出现(P<0.01)、缩短其心律失常的持续时间(P<0.01);但上述作用可被M3受体阻滞剂4-DAMP完全逆转。结论匹罗卡品通过激动Wistar大鼠心肌M3受体而产生对抗乌头碱和氯化钡诱发Wistar大鼠心律失常的作用。     

HPLC法测定硝酸毛果芸香碱注射液的含量与有关物质

目的:建立高效液相色谱法测定硝酸毛果芸香碱注射液的含量及有关物质。方法:采用C18柱,流动相为甲醇-含0.002mol.L-1磷酸二氢铵和0.0018 mol.L-1四丁基氢氧化铵的水溶液(30∶70),检测波长220 nm。用外标法测定含量,不加校正因子的自身对照法测定有关物质。结果:有关物质浓度在0.510～153.1μg.mL-1,含量测定浓度在51.58～515.8μg.mL-1范围内与峰面积呈良好的线性关系。硝酸毛果芸香碱主成分峰与有关物质峰的分离度均符合要求,硝酸毛果芸香碱的检出限为4 ng。结论:本方法简便、准确,灵敏度高,适用于该制剂的含量及有关物质测定。     

褪黑素对匹罗卡品致痫模型鼠行为改变的影响

目的　探讨褪黑素在匹罗卡品致痫大鼠模型中的抗癫痫作用及其机制。方法　采用匹罗卡品癫痫模型,观 察长期给予褪黑素对匹罗卡品致痫大鼠原发性癫痫反复发作、海马神经元丢失,苔癣纤维轴突发芽的影响。结果　给予 褪黑素后匹罗卡品致痫大鼠原发性癫痫反复发作出现的潜伏期延长,发作程度和频率均降低(P<0.01);给予褪黑素治疗 的大鼠海马CA1区Nissl染色和Timms染色评分均明显低于未用褪黑素处理的致痫大鼠(P<0.01)。结论　褪黑素能明显 降低匹罗卡品致痫大鼠原发性癫痫反复发作的频率和程度,该作用可能与褪黑素对海马神经元损伤的保护及对苔癣纤维 轴突发芽的抑制作用有关。