On the mode of action of diazepam on brain catecholamine metabolism

Intraperitoneal injection of diazepam in moderate dosage (1--10mg/kg) to rats caused a decrease in dopa and 5-hydroxytryptophan (5-HTP) formation, measured as the accumulation of these intermediates induced by inhibition of the aromatic L-aminoacid decarboxylase by means of NSD 1015 (3-hydroxybenzylhydrazine (HCl), in limbic forebrain, striatum and the remaining hemisphere portion. These effects are opposite to those induced by gamma-aminobutyric acid (gaba) and gamma-butyrolactone (100 and 750 mg/kg i.p. respectively), and the effects of the latter agents were significantly counteracted by diazepam. The effect of diazepam on dopa formation persisted after the acute transection of dopaminergic axons (transverse cerebral hemisection at the level of the caudal hypothalamus). The elevation of dopamine following hemisection was also significantly counteracted on the hemisected side of the brain, the intact side remaining unchanged. The data do not support the hypothesis that benzodiazepines act by enhancing gabaergic transmission. They rather suggest that these agents exert an inhibitory action on transmitter synthesis and utilization at the synaptic level, i.e. an action not necessarily bearing any direct relationship to gaba.

The effect of intracerebroventricularly administered GABA on brain monoamine metabolism

Intracerebroventricular injection of gamma-aminobutyric acid (GABA) was performed in male rats and the brain monoamines, 5-hydroxyindoleacetic acid (5-HIAA), tyrosine and tryptophan levels were measured. GABA induced within 30 min a marked dose-dependent increase in the brain contents of dopamine (DA), serotonin (5-HT), tyrosine and tryptophan, while noradrenaline (NA) was lowered. Large doses of GABA, i.e. 1.5-3 mg/rat, were required for these effects. Aminooxyacetic acid (AOAA), an inhibitor of GABA-transaminase, when given alone in a dose of 25 mg/kg i.p. caused a significant rise of DA, 5-HT and tryptophan. The combination of GABA and AOAA raised these levels more than either agent alone. Picrotoxin (4 mg/kg, i.p.) a claimed GABA receptor antagonist partially counteracted the GABA-induced DA rise. Monoamine synthesis was studied in different parts of the brain by measuring the accumulated dopa and 5-hydroxytryptophan (5-HTP), 30 min after NSD 1015 (3-hydroxybenzylhydrazine HCl, 100 mg/kg) an inhibitor of aromatic L-amino-acid decarboxylase, given i.p. 5 min after GABA. GABA caused a marked rise in dopa formation both in DA- and NA-predominated brain regions. Also 5-HTP formation was enhanced. The effects on both dopa and 5-HTP formation showed marked regional differences. The data suggest that GABA, by activating specific receptors, causes inhibition of firing of dopaminergic neurones and the opposite effect on the noradrenergic neurones. The nature of the effect on 5-HT metabolism needs further investigation.

The effect of intraperitoneally administered GABA on brain monoamine metabolism

GABA was injected intraperitoneally to rats in single doses of 2.5 to 1500 mg/kg. Thirty minutes after injection a dose-dependent increase in dopamine (DA) and a decrease in noradrenaline (NA) content were observed in the brain. However, in the lowest dose range these levels showed small but significant changes in the opposite direction. The accumulation of dopa after inhibition of the aromatic L-aminoacid decarboxylase was enhanced by i.p. GABA both in DA- and in NA-predominated brain regions, the dose-response relations being complex. Increased levels of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and tryptophan as well as enhanced accumulation of 5-hydroxytryptophan, induced by decarboxylase inhibition were also observed. The general pattern of effects was similar to that previously observed after intracerebroventricular injection of GABA, although the intraperitoneal doses required were higher. It is suggested that a certain penetration of GABA from the blood into the brain can occur, leading to changes in the physiological activity of monoaminergic neurons.

Adrenocortical changes in rats during acute and chronic administration of delta-9-tetrahydrocannabinol

Acute intraperitoneal administration of delta-9-THC (at doses of 10 mg/kg and 50 mg/kg) to adult male albino rats showed characteristic stimulating effect on adrenocortical tissues with marked depletion of ascorbic acid, cholesterol containing neutral lipids and significant increase in the delta5-3 beta -hydroxysteroid dehydrogenase and glucose-6-phosphate dehydrogenase activities in the zona fasciculata and zona reticularis regions. Adrenal weights and the histometric measurements of the adrenocortical areas showed no significant changes. Chronic intraperitoneal administration of delta-9-THC (at doses of 10 mg/kg per day for 15 days) produced marked accumulation of cholesterol containing neutral lipids, with increase in ascorbic acid and delta5-3 beta-hydroxysteroid dehydrogenase and glucose 6-phosphate dehydrogenase activities in the fasciculata-reticularis regions. Adrenal weights and histometric measurements revealed marked hypertrophy of the adrenal glands.

Quantitative study of uterine curettage in the menstrual cycle

The histological appearances in 114 endometrial curettings from cases of dysfunctional bleeding have been analysed quantitatively by the method of Dunnill and Whitehead (1972) and Risdon and Keeling (1974). As applied to this type of specimen, the technique provides indices of both tubular volume and tubular surface to volume ratio. The histological diagnosis of endometrial hyperplasia is made from the increase in stromal and epithelial elements and the change in the pattern of the glands. These changes, on some occasions, can be difficult to detect. Quantitative analysis can be used to distinguish minor degrees of abnormal endometrial hyperplasia, in comparing serial endometrial changes in a given patient, and in comparing different menstrual cycles in dysfunctional uterine bleeding. Endometrial biopsies were collected and put in categories according to the clinical diagnosis. These biopsies were then examined morphometrically to find the volume/glandular surface and glandular/volume ratio. A significant change in these ratios was found.

Changes in rat adrenal medulla following delta9-tetrahydrocannabinol treatment. A histochemical study

The effects of acute (10 mg/kg) and chronic 10 mg/kg for 30 days) administration of delta-9-tetrahydrocannabinol (delta9-THC) have been studied histochemically in the rat adrenal medulla, which include total catecholamines, noradrenaline, histometric measurements of adrenal medullary areas, calcium content of the medullary cells along with adenosine triphosphatase (ATPase), acetyl cholinesterase (AChE) and butyryl cholinesterase (BChE) activities. Acute delta9-THC treatment reduced the total catecholamine content (including noradrenaline) of the gland, was accompanied by increased ATP-ase, AChE, BChE activities and increased calcium distribution in the gland. Chronic delta9-THC treatment caused significant hypertrophy of the chromaffin tissue, with decreased total catecholamine content, although noradrenaline containing areas exhibited no notable change. The calcium content and ATPase activity were increased along with a concomitant increase in AChE and BChE activities. Although the changes in adrenal medullary enzyme activities following both acute and chronic delta9-THC treatment are qualitatively similar, marked quantitative increase is noted in the chronically treated groups. The results indicate an increased total catecholamine releasing activity of the adrenal medulla following acute delta9-THC treatment, while chronic delta9-THC administration produces a preferential release of adrenaline.