Biomedical subjects

H Cramer

Publications and source records attributed to H Cramer.

At least 127 records · Page 7Linked to original sources

PubMed1976

[Effects of levodopa and piribedil on cyclic AMP levels in cerebrospinal fluid in rats (author's transl)].

30 min after injection of levodopa (200 mg/kg) into rats the cAMP levels in the cisternal fluid were significantly elevated by 60% over controls. When dopamine-beta-hydroxylase was inhibited by bis-(4-methyl-1-homopiperazinyl-thiocarbonyl)-disulfide (Fla 63) the levodopa induced increase of cAMP levels was less marked, it was suppressed by propranolol (10 mg/kg), a beta-adrenergic blocking agent. Piribedil (10 mg/kg) failed to influence cisternal cAMP concentrations. The findings do not support the concept of a dopamine-sensitive adenylate cyclase in vivo, and suggest a beta-adrenergic stimulation of cerebral adenylate cyclase by metabolites of levodopa.

Animals↗

PubMed1976

Effects of compound 48/80, a histamine-releasing agent, on accumulation and release of cyclic AMP in various regions of rat brain in vitro.

The effect of compound 48/80 in various rat brain regions - by means of incubating brain sclices with compound 48/80 - on cyclic AMP accumulation and release of the nucleotide into the incubation medium was studied. In all regions tested, accumulation of cyclic AMP occurred within at least 10 min. In the cortex, brain stem and cerebellar regions these increases of cyclic AMP could be blocked by propranolol, a beta-adrenergic antagonist. Diphenhydramin, an antihistaminic agent, was without effect in these regions, but could partially block the compound 48/80-induced rise of cyclic AMP in the hypothalamus. Propranolol had in this region only a moderate blocking effect. Release of cyclic AMP, induced by compound 48/80, occurred in all regions tested and could not be effectively blocked by propranolol or diphenhydramin.

Adenylyl Cyclases↗

PubMed1976

[Liberation of growth hormone and melanocyte-stimulating hormone in natural and melatonin-induced human sleep (author's transl)].

As in the early period of night sleep, plasma levels of human growth (HGH) are markedly elevated in afternoon sleep in healthy young males. Melatonin (50 mg i.v.) induces marked secretion of HGH when sleep is prevented. It decreases latencies for sleep onset and deep sleep significantly, and markedly enhances peak secretion of HGH during slow-wave sleep. Plasma melanocyte-stimulating hormone (betal-MSH) levels were influenced neither by melatonin nor by sleep.

Growth Hormone↗

PubMed1975

Cyclic adenosinemonophosphate in cerebrospinal fluid. Effects of theophylline, L-dopa and a dopamine receptor stimulant in rats.

The effects of L-Dopa and the dopamine receptor stimulant ET-495 on cisternal cAMP levels were studied in rats. L-dopa (100-200 mg/kg) increased cisternal cAMP levels by 60 to 80% of controls. When peripheral Dopa-decarboxylase was inhibited, smaller doses of L-Dopa were effective. Fla-63, an inhibitor of dopamine-beta-hydroxylase lowered the increase induced by L-Dopa which was completely suppressed by propranolol, not by phentolamine, suggesting that the cAMP increase is mediated through a central beta-adrenoceptor stimulation. ET-495 failed to influence cAMP levels which argues against a dopamine-sensitive adenylate cyclase involved in the L-Dopa effect. Moreover, large increases of cisternal cAMP were observed after treatment with theophylline , not papaverine which suggests different effects of these "phosphodiesterase inhibitors" on the cyclic AMP systems in the central nervous system or on transport mechanisms.

Animals↗

PubMed1975