The effects of nicotine receptor agonists on the release of [3H]acetylcholine from the phrenic nerve, the small intestine and the trachea were investigated to characterize neuronal nicotine receptors within the peripheral nervous system. Contraction of the indirectly-stimulated hemidiaphragm was recorded to investigate desensitization of the postsynaptic muscular nicotine receptors. Nicotine, cytisine, 1,1-dimethyl-4-phenylpiperazinium and 2-(4-aminophenyl)-ethyl-trimethyl-ammoniumiodide caused a concentration-dependent (0.1-30 microM) increase in evoked [3H]acetylcholine release from the phrenic nerve, whereby bell-shaped concentration-response curves were obtained. The rank order of decreasing potency was: nicotine greater than cytisine greater than 1,1-dimethyl-4-phenylpiperazinium greater than 2-(4-aminophenyl)-ethyl-trimethyl-ammoniumiodide. The presynaptic effects of nicotine depended strongly on the exposure time: facilitation occurred after a short 20 s exposure and inhibition after a 3 min exposure, whereas nicotine no longer affected evoked [3H]acetylcholine release after a 15 min exposure. Pre-exposure (40 min) of the phrenic nerve to 0.3 microM nicotine prevented any subsequent modulatory effect of a high nicotine concentration. In contrast, the contraction of the indirectly-stimulated hemidiaphragm remained unaffected in the presence of 0.3-30 microM nicotine, but a concentration of 1 mM nicotine abolished skeletal muscle contraction. Nicotine (10 microM) produced a substantial release of [3H]acetylcholine in the small intestine but not in the isolated trachea. The present experiments show presynaptic nicotine receptors at the phrenic nerve, which, under appropriate conditions, can mediate facilitation of evoked transmitter release. These neuronal receptors appear more sensitive to desensitizing conditions than the postsynaptic muscular nicotine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMedDate not supplied

The effect of chronic vs. acute injection of vasopressin on animal learning and memory.

The effect of chronic and acute treatment with DDAVP, a vasopressin analog, was studied in 2 month old male rats, using an active avoidance test in a shuttle box. The experiment lasted 6 weeks: an acquisition period of 4 weeks and an extinction period of 2 weeks. Rats were treated one hour before behavioral testing 3 times a week for 6 weeks with either DDAVP 20 micrograms/rat/day for the whole period (chronic group) or with DDAVP for the first week and again once only on the first day of the extinction period (acute group) or with saline. Chronic treatment with DDAVP resulted in better acquisition and in a marked retardation of extinction compared with the acute treatment group. These results were obtained both in normal rats and in rats pretreated at age 5 days of life with intracisternal 6-OH dopamine.

Animals↗

PubMedDate not supplied

Effects of nimodipine and other calcium channel antagonists in alcohol-preferring AA rats.

Several lines of evidence suggest that L-type calcium (CA2+) channels play a role in excessive ethanol (EtOH) intake. In accordance with this, a considerable amount of antagonists for these ion channels has been found to suppress EtOH intake and preference in various animal models of alcoholism. The aim of the present study was to examine antialcohol effects of L-type Ca2+ channel antagonists in alcohol-preferring AA rats. These rats, a Wistar line selectively bred for a high 10% v/v EtOH preference in a free-choice situation, have thus far not been subjected to systematic investigations with Ca2+ channel antagonists. Therefore, effects on EtOH preference and intake, as well as on food and total fluid intake, were evaluated for the 1,4-dihydropyridine (DHP) derivatives nimodipine, felodipine, isradipine, nicardipine, nifedipine, and nitrendipine, as well as for the phenylalkylamine verapamil and the benzothiazepine diltiazem, utilizing a limited access, free-choice procedure. All DHPs were found to be highly effective in reducing both EtOH intake and preference, without affecting total fluid intake. Irrespective of route of application (IP or PO), the effective dose ranges were found to be very similar across compounds (10-30 mg/kg). Nevertheless, because food intake was also reduced, the effects were not completely selective. For nimodipine, the (-)-enantiomer seemed to be more effective as its (+)-enantiomer, possibly reflecting stereoselectivity at central binding sites. Compared to the DHPs, verapamil produced a similar profile of activity, but diltiazem was found to be ineffective. These results confirm and extend previous findings with L-type Ca2+ channel antagonists obtained in other models of alcoholism and suggest that this class of compounds offers an interesting approach for the pharmacotherapy of alcoholism.

Alcohol Drinking↗

PubMedDate not supplied

Intrahepatic, extramedullary hematopoiesis mimicking hemangioma on technetium-99m red blood cell SPECT examination.

Cavernous hemangiomas are the most common lesion of the liver. Because of the risk of hemorrhage inherent in percutaneous biopsy of such lesions, noninterventional modalities (such as CT, ultrasound, MRI and Technetium-99m red blood cell imaging) have been utilized for differentiating them from other lesions. The sensitivities and specificities of these techniques vary greatly. Technetium-99m red blood cell imaging with planar and SPECT imaging has been shown to have an overall sensitivity of 89%, a specificity of 100%, and an overall accuracy of 92%. Despite its high accuracy, rare false positives have been reported with Technetium-99m red blood cell imaging with SPECT. Review of the literature indicates four cases of hepatocellular carcinoma, one case of hepatic angiosarcoma, and one case of hepatic metastases from colorectal carcinoma as having an appearance identical to hemangioma with this modality. We present an additional false positive of a focal region of intrahepatic extramedullary hematopoiesis in a patient with Gaucher's disease as having an appearance on Technetium-99m red blood cell imaging with SPECT identical to that of hemangioma.

Animals↗

PubMedDate not supplied

The stability of bacteriophages in long term storage at liquid nitrogen temperatures.

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Bacteriophages↗