Toshihisa Tajima

Immobilization stress-induced increase of hippocampal acetylcholine and of plasma epinephrine, norepinephrine and glucose in rats

We investigated the role of the hippocampal cholinergic neurons during immobilization stress in rats using a microdialysis technique. Blood levels of glucose, epinephrine and norepinephrine during immobilization stress were also determined. Acetylcholine release was initially increased by immobilization stress, then gradually decreased. Plasma level of epinephrine increased gradually and reached significance at 30 min after the start of immobilization and remained at the elevated level during immobilization. Plasma level of norepinephrine initially increased and reached significance at 30 min after the start of immobilization and remained at the elevated level during immobilization. Plasma level of glucose increased gradually and reached maximum and significance 45 min after the start of immobilization, then decreased. Fifteen min after immobilization, acetylcholine release increased again, while concentrations of epinephrine and norepinephrine were still elevated. Thus the response of acetylcholine and the other responses to immobilization stress were not parallel.

Swimming stress that causes hyperglycemia increases in vivo release of noradrenaline, but not acetylcholine, from the hypothalamus of conscious rats.

The effects of acute swimming stress (10 min) on noradrenaline release from the medial basal hypothalamus (MBH; consisting of the ventromedial and dorsomedial hypothalamus) and acetylcholine release from the lateral hypothalamic area (LHA) were investigated in freely moving rats by using in vivo microdialysis techniques. Serum glucose, noradrenaline and adrenaline concentrations were also determined. Acute swimming stress produced significant hyperglycemia, with increases in serum noradrenaline and adrenaline concentrations. The release of noradrenaline from the MBH was significantly stimulated during the swimming stress. On the other hand, the swimming stress has no significant effect on the release of acetylcholine from the LHA. These findings support the idea that hypothalamic noradrenergic neurons play an important role in the sympathoadrenal hyperglycemic response to stressful stimuli. Moreover, it is suggested that hypothalamic cholinergic neurons are not involved in the responses of serum glucose, noradrenaline and adrenaline concentrations to swimming stress.

Dietary restriction of choline reduces hippocampal acetylcholine release in rats: in vivo microdialysis study.

We fed rats with a diet deficient in choline for 12 weeks and studied how dietary choline deficiency affected their behavior and their ability to release acetylcholine in discrete regions of rat brain using step-through passive avoidance task and in vivo microdialysis. In comparison with the control, rats fed the choline-deficient diet showed poorer retention of nociceptive memory in the passive avoidance task. Average choline level in cerebrospinal fluid in the choline-deficient group was significantly less (33.1%) than that of control rats. In vivo microdialysis showed no difference in the pattern of acetylcholine release enhanced by intraperitoneal administration of scopolamine hydrochloride (2 mg/kg) in the striatum between the two groups, whereas in the hippocampus, the maximum and subsequent increase of acetylcholine from the baseline by scopolamine injection was significantly lower in the choline-deficient group than in the control. From the results of our study, we speculate that long-term dietary restriction of choline can affect extra- and intracellular sources of substrates required for acetylcholine synthesis, and eventually limit the ability to release acetylcholine in the hippocampus. Reduced capacity to release acetylcholine in the hippocampus implies that the mechanism, maintaining acetylcholine synthesis on increased neuronal demand, may vary in discrete regions of the brain in response to dietary manipulation. The vulnerability of the mechanism in the hippocampus to dietary choline restriction is indicated by impaired mnemonic performance we observed.

Starvation reduces norepinephrine activities in both hypothalamus and heart in rats

Norepinephrine (NE) activities in both hypothalamus and heart were simultaneously assessed in rats after food-deprivation for 2 days. The technique of gas chromatography-mass spectrometry was employed for the analysis of NE and its primary neuronal metabolite, 3,4-dehydroxyphenylethylene glycol (DHPG), and the ratio of DHPG to NE was used as an index of NE activity. Hypothalamic DHPG/NE ratio was significantly decreased by fasting and was completely reversed by a single day of refeeding. These changes in hypothalamic DHPG/NE ratio were parallel to those in cardiac DHPG/NE ratio. Supporting the concept in which hypothalamic NE neurons play an important role in modulating the sympathetic outflow, it is suggested the decrease in hypothalamic NE activity contributes to the reduction in cardiac NE activity during fasting.

Pharmacokinetic study of aniracetam in elderly patients with cerebrovascular disease

The clinical pharmacokinetics of the cognitive enhancer, aniracetam (200 mg), was studied in elderly patients with cerebrovascular disease (CVD) and compared with those of young healthy volunteers. Six female hospitalized patients (mean age 84.5 years) were used in this study. The serum level of anisic acid and p-methoxyhippuric acid, major metabolites of aniracetam, reached a peak at 2 h after oral administration, and returned to basal level by 6 h. Mean creatinine clearance was 20-30 ml/min. The t1/2 of metabolites was increased by 4- to 7-fold in the elderly patients compared with young volunteers. This study showed that tmax, t1/2, and AUC were enlarged in the elderly; however, no clinical side effects were observed.

Adrenocorticotropin and growth hormone secretions after intracerebroventricular administration of neostigmine in rats: their relationships to hypothalamic monoaminergic neuronal activities

Serum adrenocorticotropic hormone (ACTH) and growth hormone (GH) concentrations were assessed simultaneously with hypothalamic neuronal activities of norepinephrine (NE), dopamine (DA), and serotonin (5-HT) 60 min after the third cerebroventricular administration of neostigmine (a cholinesterase inhibitor) in awake rats. Serum ACTH and GH concentrations were significantly increased and decreased, respectively. Neostigmine caused significant increases in hypothalamic NE and DA activities and a significant decrease in hypothalamic 5-HT activity. The reciprocal changes of serum ACTH and GH concentrations were similar to those of hypothalamic NE and 5-HT activities. Multiple regression analyses with stepwise procedure revealed that hypothalamic NE and 5-HT activities were respectively significant determinants of serum ACTH and GH concentrations. Apart from the direct influence of neostigmine on ACTH and GH secretions, it is suggested that the changes in hypothalamic monoaminergic activities play an important role in modulating ACTH and GH secretions following the administration of neostigmine.

Some Effects of CNS Cholinergic Neurons on Memory and ACh Release

The aim of this study is to observe the relationship between the impairment in passive avoidance task induced in rats by the i.p. administration of muscarinic antagonists, scopolamine and methyl-scopolamine, and the changes in acetylcholine (ACh), monoamines output induced by these drugs. Initially we studied the effects of these drugs on the animals’ performance of a step-through passive avoidance task. We then measured the change in ACh and monoamines levels after administration of these drugs using an in vivo brain dialysis technique. Scopolamine was effective in impairing the performance of the passive avoidance task, while methyl-scopolamine did not have clear effects on the performance of the task. With regard to ACh output, scopolamine increased ACh dose-dependently and methyl-scopolamine also affected ACh release. Scopolamine did not affect monoamines release except serotonin.

Therapeutic outcome of onabotulinum toxin type A in patients with upper limb spasticity

Onabotulinum toxin type A treatment for post-stroke upper limb spasticity was investigated to contribute to establishing a standard dosage for Japanese patients. A total of 100 patients participated in the study. The outcome one month (33.6±6.5 days) after the treatment was assessed by the Modified Ashworth Scale (MAS) to estimate the mean effect with a 10-unit injection and the standard dosage expected to improve MAS 1 degree. Average improvement of 263 muscles treated with a higher concentration of 10 units diluted in 0.2 ml was 0.207±0.414 degrees, and that of 231 muscles treated with a lower concentration of 10 units in 0.4 ml was 0.149±0.244 degrees without significant difference among diluted concentrations. To improve MAS 1 degree, 64.6±31.1 units were required for the pectoralis major, 51.2±21.3 units for the teres major, 111.7±48.0 units for the biceps brachii, 51.6±26.8 units for the brachioradialis, 54.1±23.2 units for the brachialis, 34.4±10.7 units for the pronator teres, 64.6±27.9 units for the flexor carpi radialis, 62.4±26.8 units for the flexor carpi ulnalis, 58.5±31.1 units for the flexor digitorum profundus, 69.7±35.1 units for the flexor digitorum superficialis, 24.6±13.4 units for the flexor pollicis longus, and 15.6±11.3 units for the adductor pollicis. Although the results shown here had no significant differences among concentrations, increasing the volume would disturb injection into small muscles, so we considered that a lower volume with a higher concentration should assure larger benefits. It is difficult to make effective injections into all spastic muscles within the officially permitted health insurance dosage of 240 units. Hence, it is advisable to increase the applicable upper limit based on safely achieved cumulative experience.