Correlation between in vitro and in vivo models of proconvulsive activity with the carbapenem antibiotics, biapenem, imipenem/cilastatin and meropenem.

The present study evaluated the proconvulsant liability of biapenem, a novel carbapenem antibiotic, in in vitro and in vivo experiments, in comparison with the carbapenems, imipenem/cilastatin and meropenem. Imipenem/cilastatin is a carbapenem antibiotic with known proconvulsive liability in man and in animal experiments. In in vivo studies imipenem/cilastatin, at doses of 400/400 mg/kg i.v., significantly lowered the convulsive threshold of pentylenetetrazol (PTZ) in mice and shifted the dose-response curve of PTZ. The effects of biapenem (400 mg/kg i.v.) and another reference carbapenem, meropenem (400 mg/kg i.v.), in the mouse PTZ model were not significantly different from control. In in vitro experiments the carbapenems were tested for their ability to inhibit [3H]muscimol (1.3 mM) binding to rat brain homogenates at concentrations of 1-10 mM. Similar to in vivo results, when compared to imipenem/cilastatin, biapenem and meropenem did not inhibit [3H]muscimol binding to the GABAA receptor complex in brain homogenates while imipenem/cilastatin exhibited significant inhibition (IC50 = 4.6 mM). These results further confirm the correlation between in vitro GABAA binding and in vivo PTZ convulsive testing with carbapenem antibiotics, and suggest that biapenem possesses a low proconvulsive liability.

The effect of microwave irradiation on vasopressin in plasma and hypothalamo-neurohypophyseal system.

Radioimmunoreactive vasopressin was measured in plasma, neurohypophysis and hypothalamus of the rats after different procedures of killing: a) microwave irradiation; b) decapitation; c) decapitation following a stress induced by immobilization in a restrainer. Vasopressin content in the neurohypophysis and hypothalamus was much lower in microwave irradiated than in both decapitated and stressed decapitated rats. In addition, the data from microwave technique were inconsistent with a large scatter. Plasma vasopressin concentration was elevated in both the microwave irradiated and stressed decapitated rats, demonstrating that restraining of the animals induced an excessive stress. Microwave irradiation technique including the necessary manipulation of the animal proved to be less suitable than decapitation technique for the measurement of vasopressin. It is likely that vasopressin in the hypothalamus and neurohypophysis is relatively resistant against post-mortem proteolysis.

Thiophene systems. 5. Thieno[3,4-b][1,5]benzoxazepines, thieno[3,4-b][1,5]benzothiazepines, and thieno[3,4-b][1,4]benzodiazepines as potential central nervous system agents.

10-(Alkylamino)thieno[3,4-b][1,5]benzoxazepines (3) and 10-(alkylamino)thieno[3,4-b][1,5]benzothiazepines (4) were prepared by derivatization of the respective lactams (7 and 8) via phosphorus pentachloride and subsequent condensation with the appropriate alkylamines. 9-(Alkylamino)-4H-thieno[3,4-b][1,4]benzodiazepines (5) were prepared by titanium tetrachloride catalyzed condensation of the lactam 11 with alkylamines. 9-(Alkylamino)-4-methylthieno[3,4-b][1,4]benzodiazepines (6) were prepared by reductive alkylation of 5. The compounds were tested for potential neuroleptic activity by means of the blockade of d-amphetamine lethality in aggregated mice and/or effects on locomotor activity in rats. Antidepressant activity was examined using inhibition of tetrabenazine-induced depression in mice. Most of the title compounds 3-6 were found to have neuroleptic activity. In addition, introduction of a 3-chloro substituent in the oxygen and sulfur systems (3p and 4c), as well as introduction of an N-alkyl in the dinitrogen system (6), was found to produce antidepressant effects. Structure-activity relationships are discussed.

Derivatives of 11-(1-piperazinyl)-5H-pyrrolo[2,1-c][1,4]benzodiazepine as central nervous system agents.

Four 11-(1-piperazinyl)-5H-pyrrolo[2,1-c][1,4]benzodiazepines were prepared and evaluated as central nervous system agents. All were active psychotropic agents as determined by animal screening tests. The most interesting compound, 11-(1-piperazinyl)-5H-pyrrolo[2,1-c][1,4]benzodiazepine, showed dual activity as an antidepressant against tetrabenazine depression and as a neuroleptic as measured by protection vs. amphetamine lethality in grouped mice.

10-(Alkylamino)-4H-thieno[3,4-b][1,5]benzodiazepines. A novel class of potential neuroleptic agents.

An investigation of the structural requirements for CNS activity of the title compounds was undertaken. A synthesis of the precursor dihydro-10H-thieno[3,4-b][1,5]benzodiazepin-10-ones was achieved and three routes for their conversion to the title compounds were developed. The compounds were tested for neuroleptic activity by means of the blockade or d-amphetamine lethality in aggregated mice and/or effects on locomotor activity in rats. Antidepressant activity was examined using inhibition of tetrabenazine-induced depression in mice. Most of the compounds were found to be potent neuroleptic agents with several exhibiting additional antidepressant activity.

Derivatives of 1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H)-dione as anxiolytic agents.

A study of the pharmacological properties of pyrrolo[2,1-c][1,4]benzodiazepine derivatives led to the choice of (+)-1,2,3,11a-tetrahydro-10-methyl-5H-pyrrolol[2,1-c][1,4]benzodiazepine-5,11)10H)-dione as a candidate for anxiolytic evaluation in a limited clinical trial in man. Metabolism studies in laboratory animals have pointed to rapid hydroxylation, possibly in the 3 and 11a positions. A series of compouds containing methyl groups in one or more of these positions has been prepared in an effort to block metabolism and thereby obtain more active or longer acting compounds. All of these derivatives were less active than the parent compound.