Pharmacological testing methods for drugs acting on the peripheral nervous system

The use of trabeculectomy to study the pharmacological modulation of ophthalmic wound healing

A trabeculectomy model was developed to test the efficacy of a putative interleukin-1 blocker on the modulation of ophthalmic wound healing in the pigmented rabbit. The corticosteroid, methylprednisolone acetate, was used as a positive control and was effective in prolonging the time to failure of the trabeculectomy. The experimental compound CK-103A was found to be more efficacious than methyl prednisolone acetate. CK-103A increased the time of failure by 79%, with no side effects at the doses tested to date.

Pressor responses to central injection of H2 antagonists not caused by GABA blockade

In awake rats, ranitidine was more effective than cimetidine in elevating blood pressure following intracerebroventricular (i.c.v.) injection, yet neither drug affected the hypotensive response to subsequent injections of muscimol (8.8 nmol i.c.v.). Bicuculline (0.01 nmol) microinjected into the inferior colliculus of rats caused clonic seizures whereas cimetidine (100 nmol) had no effect. The antihistamines did not prevent GABAB receptor-mediated inhibition of twitch responses in transmurally stimulated guinea-pig ileum. Ranitidine potentiated rather than inhibited GABAA receptor-mediated contractions of ileum longitudinal muscle. Cimetidine had no effect on these responses except at high concentrations (3 X 10(-4) M) which caused a slight dextral shift in the contractile response curve for GABA that may be attributed to antimuscarinic actions of cimetidine. Taken together, these data do not support the concept that the centrally mediated pressor effects of H2 antagonists are caused by GABA receptor blockade.

Ranitidine potentiates ileum contractions caused by GABA and electrical stimulation

GABA-evoked contractions of the guinea pig ileum were significantly potentiated by the histamine H2-receptor antagonist ranitidine in concentrations above 10 microM. To help define the mechanism of this interaction, the present study compared the effects of ranitidine on contractile responses of the guinea pig ileum to GABA, acetylcholine (A Ch) and electrical stimulation of intrinsic cholinergic neurons. Ranitidine, at concentrations that potentiated responses to GABA, also potentiated contractions induced by transmural electrical stimulation. The ability of ranitidine to amplify these latter responses was antagonized by atropine. Contractile responses to exogenous A Ch, however, were unaffected by ranitidine at any concentration. These results suggest that prejunctional, rather than postjunctional mechanisms, are of primary importance in the interaction between ranitidine and GABA.

A multi-chemical death involving caffeine, nicotine and malathion

Death of a 21-year-old man who was found in a shower stall in his residence is described in the study. At the scene, a 3/4 filled blue glass bottle labeled "Black Leaf 40" (an insecticide containing nicotine), a white plastic pitcher 1/3 full of thick white fluid, a beer mug 1/4 full of thick white fluid, and an empty carton of milk were found. In addition, a can of malathion and an empty bottle labeled caffeine also were found in the vicinity. Autopsy was performed, and the gross examinations of organs revealed no specific findings to account for the death. However, marked congestion in lung, liver, spleen and kidney were noted at microscopic level. Autolytic degenerative changes were also observed in stomach, small bowel and colon. Toxicological analyses of the autopsy samples (blood, urine, liver and gastric contents) revealed the presence of caffeine and nicotine in each sample. Malathion was found to be present only in gastric content. Caffeine and nicotine were analyzed by utilizing gas liquid chromatography-nitrogen phosphorus detector, while malathion was by gas liquid chromatography-flame photometric detector. Analyses of the fluids from the bottle, pitcher and mug disclosed the presence of nicotine in the concentrations of 17.8%, 3.7% and 5.7% (w/w), respectively. The fluids from the pitcher and mug also contained 2.7-2.9% malathion. Results conclude the death was associated with caffeine, nicotine and malathion.

The pharmacological evaluation of natural products--general and specific approaches to screening ethnopharmaceuticals

Natural product research is most efficiently conducted in a systematic fashion concentrating on ten critical questions which must be answered in sequential fashion by thoroughly trained professionals experienced in such research. The minimum ethnopharmacology research team should consist of a botanist, a chemist and a pharmacologist with each carrying the responsibility for answering certain of the critical questions. The screening procedures used for the evaluation of synthetic medicinals generally are not appropriate for guiding the extraction of active principles from crude drugs and establishing extraction efficiency; therefore, specialized techniques unique to ethnopharmacology must be used.

Vasodilator activity of adenosine analogs

Various adenosine analogs were evaluated as smooth muscle vasodilators. The compounds were screened ititially using a dog hindlimb preparation. Most analogs were less potent than adenosine. The three most potent compounds were tested for coronary vasodilator effects and duration of action on the isolated rabbit heart. 5'-Deoxy-5'-chloroadenosine and 5'-deoxy-5'-bromoadenosine were equipotent with adenosine but possessed a longer duration of action 2',3',5'-Trideoxy-3',5'-dichloroadenosine, an analog lacking both the 2'- and 3'-hydroxyl groups, had significant vasodilator activity.

In vivo effects of some tertiary alkylaminoethyl esters with choline acetyltransferase inhibitory properties

The tertiary nitrogen derivatives of two choline esters, chloroacetylcholine and acrylcholine, known to inhibit choline acetyltransferase (ChAc) in vitro, were tested for their effects in the whole animal, including peripheral and central cholinergic systems. These esters are N,N-dimethylaminoethyl chloroacetate (Cl-DMA) and N,N-dimethylaminoethyl acrylate (acryl-DMA). The peripheral preparations studied included a neuromuscular junction, a sympathetic ganglion and a postganglionic parasympathetic exocrine preparation. Both Cl-DMA and acryl-DMA blocked responses in these preparations when injected intravenously. The LD50 values for Cl-DMA and acryl-DMA were 640 mg/kg and 183 mg/kg, respectively. Cl-DMA and acryl-DMA were also able to inhibit brain ChAc when injected intravenously by 32% and 18.5%, respectively. The brain levels of acetylcholine (ACh) were significantly reduced by about 25% with Cl-DMA but not significantly with acryl-DMA when the animals were forced to exercise after injection. It is obvious that ChAc inhibition is not effective in decreasing ACh levels significantly under normal conditions.

Pharmacology of nadolol (SQ 11725), a beta-adrenergic antagonist lacking direct myocardial depression

SQ 11725 was approximately 1/3 as potent as propranolol in blocking the stimulant effects of isoproterenol in vitro, but was 2-4 times more potent than propranolol in blocking the diastolic blood-pressure and heart-rate responses, respectively, to isoproterenol in vivo. SQ 11725 had no depressant effects on contractile force of isolated guinea pig atrial muscle at the largest bath concentration studied (1000 mug/ml), whereas propranolol caused significant depression at a concentration of 1-10 mug/ml. Propranolol was at least 20-30 times more depressant than SQ 11725 to canine myocardium in vivo. SQ 11725 was more effective then propranolol in inhibiting tachycardic responses to treadmill exercise in unanesthetized dogs. The duration of blockade of the heart-rate response to exercise or to isoproterenol administration in the unanesthetized dog was approximately 5 times greater with SQ 11725 than with propranolol.

Mouse caecum as a selective -adrenoceptor tissue

The mouse isolated caecum has been found to contain β-adrenoceptors and 5-hydroxytryptamine receptors. Conditions for optimum function of the tissue in an isolated environment are described. The preparation is sturdy, lasting, economic and dependable for the screening of potential drugs, possessing agonistic or antagonistic activity on the extra-cardiac β-adrenoceptors.