Transmucosal transport of tobramycin incorporated in solid lipid nanoparticles (SLN) after duodenal administration to rats. Part II--tissue distribution.

Tobramycin-loaded solid lipid nanoparticles (SLN) were prepared and administered by duodenal and intravenous (i.v.) routes to rats and the tissue distributions were determined successively at fixed times (30 min, 4 h and 24 h) and compared to those of the tobramycin solution after i.v. administration. The tissue distribution between tobramycin-loaded SLN administered duodenally and i.v. was different. A marked difference between tobramycin-loaded SLN administered duodenally and tobramycin solution administered i.v. was also evidenced. In particular, the amounts of tobramycin in the kidneys after tobramycin-loaded SLN administration either duodenally or i.v. were lower than after administration of i.v. solution. Tobramycin-loaded SLN were able to pass across the blood-brain barrier in rats to a greater extent after i.v. injection than after duodenal administration.

Transmucosal transport of tobramycin incorporated in SLN after duodenal administration to rats. Part I--a pharmacokinetic study.

Tobramycin-loaded solid lipid nanospheres (SLN) were prepared and administered to rats into the duodenum; their behaviour was compared to that of tobramycin-loaded SLN administered intravenously (i.v.). A tobramycin control solution was also administered to rats. Tobramycin in solution is not absorbed by the gastrointestinal route, while tobramycin incorporated in the SLN is absorbed. A high concentration of tobramycin is still present in plasma 24 hours after the duodenal administration of tobramycin-loaded SLN. Tobramycin-loaded SLN administered i.v. showed a prolonged circulation time compared to the i.v. administered tobramycin solution. The AUC of tobramycin in SLN administered duodenally is higher than those of tobramycin in SLN and in solution administered i.v.

Non-stealth and stealth solid lipid nanoparticles (SLN) carrying doxorubicin: pharmacokinetics and tissue distribution after i.v. administration to rats.

Non-stealth and stealth solid lipid nanoparticles (SLN) carrying doxorubicin were prepared as drug delivery systems. The pharmacokinetics and tissue distribution of doxorubicin in these SLN were studied after i.v. administration to conscious rats and were compared to the commercial solution of doxorubicin. The same dose of each formulation (6 mg kg(-1)of body weight) of doxorubicin was injected in the rat jugular vein. Blood samples were collected after 1, 15, 30, 45, 60 min and 2, 3, 6, 12, and 24 h after the injection. Rats were sacrificed after intervals of 30 min, 4 h, and 24 h and samples of liver, spleen, heart, lung, kidney, and brain were collected. In all samples, the concentration of doxorubicin and of the metabolite, doxorubicinol, were determined. Doxorubicin and doxorubicinol were still present in the blood 24 h after injection of stealth and non-stealth SLN, while they were not detectable after the injection of the commercial solution. The results confirmed the prolonged circulation time of the SLN compared to the doxorubicin solution. In all rat tissues, except the brain, the amount of doxorubicin was always lower after the injection of the two types of SLN than after the injection of the commercial solution. In particular, SLN significantly decreased the heart concentration of doxorubicin.

Pharmacokinetics of doxorubicin incorporated in solid lipid nanospheres (SLN).

The pharmacokinetics of doxorubicin incorporated as ion-pair into solid lipid nanospheres (SLN) was compared with that of the commercial solution of the drug. Male albino rats (Wistar-derived strain) were treated i.v. with equivalent doses (6 mg kg(-1)) of two different doxorubicin formulations: an aqueous dispersion of SLN carrying doxorubicin and a commercial doxorubicin solution (Adriablastina). These formulations were injected, under general anaesthesia, through a cannula into the jugular vein and blood samples were collected at 1, 15, 30, 45, 60, 120 and 180 min after administration. After 180 min rats were killed and samples of liver, heart, lung, kidney, spleen and brain were collected. Blood and tissue samples were analysed by a spectrofluorimetric method. The anthracycline concentration in the blood was markedly higher at each point times with the SLN than with the commercial solution. The drug concentration was also higher in the lung, spleen and brain. SLN-treated rats showed a lower doxorubicin concentration in liver, heart and kidney. The results showed that SLN increased the area under the curve (0-180 min) of doxorubicin compared to conventional doxorubicin solution and led to a different body distribution profile.

Solid lipid nanoparticles in lymph and plasma after duodenal administration to rats.

PURPOSE: To evaluate the uptake and transport of solid lipid nanoparticles (SLN), which have been proposed as alternative drug carriers, into the lymph and blood after duodenal administration in rats. METHODS: Single doses of two different concentrations of aqueous dispersions of unlabelled and labelled SLN (average diameter 80 nm) were administered intraduodenally to rats. At different times, samples of lymph were withdrawn by cannulating the thoracic duct and blood was sampled from the jugular vein. Monitoring continued for 45 and 180 minutes, for unlabelled and labelled SLN respectively. The biological samples were analysed by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and gamma-counting. RESULTS: TEM analysis evidenced SLN in lymph and blood after duodenal administration to rats: the size of SLN in lymph did not change markedly compared to that before administration. The labelled SLN confirmed the presence of SLN in lymph and blood. CONCLUSIONS: The uptake and transport of SLN in the lymph, and to a lesser extent in the blood, were evidenced. The in vivo physical stability of SLN may have important implications in designing drug-carrying SLN.

Pinch-induced catalepsy in mice: a useful model to investigate antidepressant or anxiolytic drugs.

1. Repeated pinching at the scruff produces, in experimental test/retest sessions, prolonged cataleptic-like immobility in mice that may mimic immobilities seen in some natural situations. 2. In the first experiment, on male mice, imipramine and amitriptiline (20 and 30 mg/kg i.p.) augmented the number of pinches necessary to reach the criterion of induced catalepsy and reduced the total time of catalepsy. 3. In the second experiment, on female mice, compounds that modulate the central 5-HT transmission, like fluvoxamine, fluoxetine (20 mg/kg i.p.) and ondansetron (0.1 and 1 mg/kg i.p.), retarded the occurrence and shortened the duration of pinch induced catalepsy at doses that did not modify the open field performances. Maprotiline (a selective inhibitor of the NA reuptake) did not modify the mice's performances in respect to controls. 4. Female mice presented a more rapid occurrence and a prolonged duration of pinch-induced catalepsy in respect to male controls. The present behavioral test may become a simple experimental model to detect new antidepressant or anxiolytic compounds and the significant sex difference could make the test a more useful tool in investigating anxiety behaviour in rodents.

Chronic nimodipine and yawning behavior in grouped or individually housed rats.

1. The effects of a chronic administration (around 30 mg/ kg/day) of the dihydropyridine calcium antagonist nimodipine, on apomorphine induced yawning behaviour of grouped or individual housed rats, were studied. 2. Nimodipine treatment had no effect in grouped rats. 3. Individually housed animals gave a significant lower number of yawns in respect to grouped controls: this difference disappeared in isolated, nimodipine treated, group. 4. The results show the ability of nimodipine to restore a depressed behavioural performance.

Dietary choline manipulations and behavioural modifications in rats in the early stages of aging.

1. Behavioural effects of chronic manipulations of dietary choline in rats in the early stages of aging are reported. Rats were maintained on choline-deficient, low-choline and high-choline enriched diets. Two schedules of operant conditioning, representing "learning'h situations, plus an open field session were studied. 2. In the "temporal discrimination" test, the low-choline enriched group performed significantly better than controls while the deficient-choline group worse. The high-choline enriched group performed better than controls only in the second part of the test (where there was a stabilisation in behaviour). 3. In the "extinction" trials the high-choline enriched group retarded, while deficient-choline accelerated the extinction. In the open field sessions only the deficient-choline group, for the number of squares crossed, significantly differed from controls. 4. These observations lead us to suggest a general depressive effect in the rats on a choline-deficient diet, whereas with dietary choline supplements the effects on "learning" situations can be variable depending, on a large measure, on the test chosen.

Behavioural effects of chronic manipulations of dietary choline in senescent rats.

1. Senescent rats were maintained on choline-deficient and choline-enriched diets. The modifications in rat behaviour caused by the chronic manipulations of dietary choline were studied in two schedules of operant conditioning. 2. In the "periodic conditioning" test, the schedule of reinforcement, in a 100 min trial, was changed from a fixed ratio to a fixed interval schedule. In the "reversal" test the contingency for food delivery was switched four times from one lever to the other in a two lever Skinner box. 3. In the "periodic conditioning" test, the choline enriched group (430 mg/Kg/day) showed the same reduction of responses/reinforcement as controls, from the beginning to the end of trial; in the same group the time course reduction of responses/reinforcement became significant earlier than in the control group. The deficient-choline group in the last 40 min of "periodic conditioning" trial gave a reduction of responses/reinforcement greater than controls and one rat in the group did not learn the change of experimental schedule and extinguished its operant behaviour. 4. In the "reversal" test, the choline-enriched diet (320 mg/Kg/day) improved the reinforced responses in the IV reversal; one rat of the deficient-choline group could not learn the new operant schedule since the first reversal and continued to respond on the same lever during the whole of the test.

The effect of chronic atropine administration on mouse motility and on ACh levels in the central nervous system.

Changes in mouse motility and CNS cortical and subcortical ACh levels were studied after chronic (20 days) administration of 30, 40 and 60 mg/kg/day atropine. An increase in motility similar to that induced by acute atropine administration was observed, whereas the ACh levels reduction caused by acute administration was not repeated. These results suggest that changes in mouse motility caused by atropine are not correlated to its modification of ACh levels in the CNS.

Behavioral modifications in relation to hypothyroidism and hyperthyroidism in adult rats.

1. Behavioural experiments were carried out on adult rats made hypothyroid and hyperthyroid. The hypothyroid rats in an "open field" situation reduced the number of squares crossed and boluses defecated, the hyperthyroid rats reduced the number of squares crossed. A swimming endurance was conducted to evaluate the physical resistance of the rats: only hypothyroidism affected the performance. 2. Two operant tests were studied: a) an "extinction" trial (60 min), in which the rats trained in a fixed ratio schedule (FR 1:10), were no longer rewarded with pellets of food and b) the "reversal" test in which the contingency for food delivery was switched four times from one lever, where responses were previously reinforced, to the other lever where responses had no programmed consequences. 3. Both hypo and hyperthyroid conditions caused a lower rate of responses during the "extinction" trial, while in the "reversal" test only hyperthyroid rats showed improved performances. 4. Our data clearly demonstrate behavioural changes in adult hypothyroid and hyperthyroid rats.

Action of a chronic arecoline administration on mouse motility and on acetylcholine concentrations in the CNS.

The modifications of mouse motility and of the levels of acetylcholine (ACh) in two sections of the CNS caused by a chronic administration of 4.5; 9.5; 28.5 and 60 mg kg-1 day-1 of arecoline for 20 days have been studied. At low doses (4.5 and 9.5 mg kg-1 day-1), arecoline caused no modification of the ACh levels and of the motility. The higher doses (28.5 and 60 mg kg-1 day-1) caused a reduction of the mouse motility and an increase of the ACh levels in the subcortical structures of the CNS of the mouse.

Effects of chronic manipulations of dietary choline on dynamic behavioural situations.

1. The modifications in rat behaviour caused by chronic manipulations of dietary choline were studied in two schedules of operant conditioning. Adult rats were maintained on choline-deficient, low-choline and high-choline enriched diets. 2. In the "periodic conditioning" test, the schedule of reinforcement was changed from a fixed ratio to a fixed interval schedule. In the "reversal" test the contingency for food delivery was switched four times from one lever to the other in a two lever Skinner box. 3. In the "periodic conditioning" test, control and treated groups showed the same reduction of responses/reinforcement from the beginning to the end of trial. The time-course reduction of responses/reinforcement became significant in the high-choline (331 mg/kg/day) and deficient-choline groups earlier than in the low-choline (75 mg/kg/day) enriched and control groups. 4. In the "reversal" test, the low-choline (110 mg/kg/day) enriched diet improved the reinforced responses in the IV reversal; the high-choline (330 mg/kg/day) diet gave a significant impairment of the reinforced responses in the III and IV reversals. The deficient-choline diet caused a reduced number of the total responses and a worsening of the reinforced responses in the II, III and IV reversals.

Action of a chronic administration of mescaline in dynamic behavioural situations.

The modifications of the rat behaviour caused by a chronic administration of mescaline were studied in two schedules of operant conditioning. In the "periodic conditioning" test, the schedule of reinforcement was changed from a fixed ratio to a fixed interval schedule. Mescaline (4 mg/kg/day and 10 mg/kg/day) caused no modification of the ability of the rat to adapt its behaviour to the new experimental situation. In the "reversal test" the contingency for food delivery was switched from one lever, where responses were previously reinforced to the other lever where responses had no programmed consequences. A chronic administration of mescaline (4 mg/kg/day) caused a total incapacity of the rat to switch to the lever which became reinforced in the reversal trial. A chronic administration of 9 mg/kg/day of mescaline had an excitatory effect and the number of reinforced responses in the II and III reversals exceeded the unreinforced responses in a measure greater than in the controls.

The transition from a fixed ratio to a fixed interval schedule of reinforcement in hypo and hyperthyroid rats.

The modification of behavior caused by hypo and hyperthyroidism were studied when the schedule of reinforcement was changed from a fixed ratio to a fixed interval. The conditions of hypo and hyperthyroidism were obtained with a chronic administration of methimazole and of 1-thyroxine. The level of the modifications of thyroid activity was determined by evaluation of the basal metabolic rate and of the plasma levels of T4. Hyperthyroidism caused no modification of the rat behaviour. A difficulty in adapting to the new experimental situation (learning) was found in hypothyroidism. This effect is evident in high hypothyroidism. In low hypothyroidism a depression of the rat behaviour may interfere with the modification of the learning process.

Action of caffeine, d-amphetamine, diazepam and imipramine in a dynamic behavioural situation.

A study has been made of how the chronic administration of caffeine, d-amphetamine, imipramine and diazepam affect rat behaviour in four successive trials in which the contingency for food delivery was switched from one lever where responses were previously reinforced to the other lever where responses had no programmed consequences (reversal). A complete extinction in the first reversal was obtained with diazepam 0.3 mg/kg/day. Caffeine (6 and 18 mg/kg/day) had no effect in the first reversal and damaged rat performance in the successive reversals. Imipramine (0.6 and 4 mg/kg/day) had the same effect but only in the fourth reversal. Amphetamine (0.16 and 0.7 mg/kg/day) caused a clear damage of rat performance only in the third and fourth reversals.

Action of antidepressants, stimulants and depressants in the transition from a fixed ratio to a fixed interval schedule of reinforcement.

1. The modifications of rat behaviour caused by imipramine, amitriptyline, doxepin, amphetamine, chlorpromazine, caffeine and diazepam were studied. 2. The schedule of reinforcement was changed from a fixed ratio to a fixed interval schedule. 3. All the studied drugs caused a depression of the rat behaviour but only tricyclic antidepressants and caffeine caused virtually no damage to the ability of the animal to adapt its behaviour to the new experimental situation.