Differential responses of citrus calli and protoplasts to culture filtrate and toxin of Phoma tracheiphila.

Nucellar calli from two citrus cultivars with known tolerance to mal secco disease were chosen as experimental material, to test the pathogen's response to culture filtrate (CF) and partially purified toxin (PPT). The response of the two calli to the CF was in reverse order to the known response of the two cultivars to natural and artificial inoculations with Phoma tracheiphila. HPLC analysis of P. tracheiphila CF indicated the presence of a relatively high level of indole acetic acid (IAA). The response of the two calli and protoplasts derived from these calli to increasing amounts of IAA in the culture media was in the same order as that of calli and protoplasts to CF. In contrast, the responses to PPT of calli and protoplasts from these two types confirmed the relative tolerance of 'Femminello' lemon and 'Tarocco' orange trees to mal secco disease.

Neonatal administration of oxytocin increases novelty-induced grooming in the adult rat.

Three-day-old Sprague-Dawley rat pups were intracisternally infused with a single dose of oxytocin (1 microgram/2 microliters) or saline, or were untreated. As adults, these animals were observed for novelty-induced grooming, analgesia measured by the hot-plate test, and behavior in the open field. Oxytocin treatment during infancy resulted in an elevation of novelty-induced grooming when compared to saline and untreated animals. There were no significant oxytocin treatment effects on analgesia response or open-field behaviors. Oxytocin given early in life may have permanent effects on certain behavioral responses to stress.

Pyroglutamic acid improves learning and memory capacities in old rats.

The effects of the arginine salt of pyroglutamic acid (2-oxo-pyrrolidone carboxylic acid, PCA) on learning and memory capacities of old rats were studied in a subchronic treatment schedule (i.p. injection of 0.1 and 1 g/kg/day for 15 days). The acquisition and extinction of active avoidance behaviour were studied in a pole-jumping test situation. The retention of passive avoidance response was examined in a step-through passive avoidance task. PCA facilitated the rate of acquisition of pole-jumping response, and inhibited the extinction of the response. The dose of 1 g/kg was more potent than 0.1 g/kg in this respect. Also in the passive avoidance task, the treatment with PCA was followed by an improvement of avoidance retention. These results indicate that PCA is a behaviourally active compound in that it improves learning and memory capacities in old rat.

Dopamine neurotransmission in the nucleus accumbens may be involved in oxytocin-enhanced grooming behavior of the rat.

Intracerebroventricular (ICV) infusion of a low dose of oxytocin enhanced novelty-induced grooming in male rats. The present experiments were undertaken to investigate whether dopamine neurotransmission in the nucleus accumbens is involved in this effect. Bilateral lesions of the nucleus accumbens by microinjections of 6-hydroxydopamine (6-OHDA) totally prevented the enhancement of grooming behavior after subsequent ICV infusion of oxytocin. Furthermore, bilateral injections of the dopamine receptor antagonist, haloperidol, into the nucleus accumbens completely suppressed grooming behavior of rats infused ICV with oxytocin. These results suggest that dopamine neurotransmission in the nucleus accumbens is involved in the behavioral response enhanced by the peptide.

Behavioral effects of acetyl-l-carnitine in the male rat.

The behavioral activity of carnitine acetylate derivative, acetyl-l-carnitine has been studied in the male rat. Intraperitoneal (IP) injection of acetyl-l-carnitine was followed by an increase in ambulation and rearing items in the open field behavior. Both the number of conditioned avoidance response (CARs) and the percentage of learners in the acquisition of shuttle-box active avoidance behavior appeared to be increased by IP or intracerebroventricular (ICV) injection of the drug at different doses. Subchronic administration of the drug mimicked the effects found after acute injection. The number of CARs in the extinction of shuttle-box active avoidance behavior appeared to be increased after acute IP or ICV injection, and after subchronic administration of acetyl-l-carnitine. The retention of passive avoidance behavior was facilitated by IP injection of the substance. The behavioral effects of acetyl-l-carnitine may involve central mechanisms, e.g., cholinergic neurotransmission in the brain.

Behavioral effects of deprenyl in aged rats.

The effects of an inhibitor of MAO-B, deprenyl, have been studied in aged male rats. Subcutaneous (s.c.) injection of deprenyl was followed by a facilitated acquisition of active avoidance behavior and a facilitated retention of passive avoidance response in a dose-dependent manner. Ambulation and rearing of aged rats in an open field were increased by deprenyl. No effect was found on grooming behavior. Apomorphine-induced stereotypies were potentiated and haloperidol-induced catalepsy was inhibited by deprenyl. Some elements of sexual behavior, i.e. latency to mounting and intromission and frequency of mounts and intromissions, were improved by deprenyl. Furthermore, deprenyl reduced the immobility of aged rats in a "despair" test, suggesting an antidepressant activity. Deprenyl seems to be effective in correcting some of the behavioral deficits of aged animals. Its behavioral effects can be related to the inhibition of cerebral MAO-B.

Quantitative alteration of grooming behavior in aged male rats.

Novelty-induced grooming was studied in aged male rats (24 months old) compared to young animals (3 months old). When put in a novel environment, aged rats exhibited a grooming activity markedly higher than that shown by young rats. Such an excessive grooming did not disappear over a 30 min observation. Furthermore, no significant difference between old and young rats was found in ambulation, rearing and defecation, as observed in an open field. It may be suggested that increased grooming activity in aged rats involves a disability to adapt to a novel environmental situation.

Somatic growth in hypophysectomized pituitary-homografted rats is promoted by prolactin.

Hypophysectomized male rats bearing a homograft of two adenopituitaries under the kidney capsule showed a significant increase in b.wt as compared to hypophysectomized non-homografted animals. Radioimmunoassay of growth hormone (GH), ACTH, alpha-MSH, beta-endorphin and prolactin (PRL) revealed that only the latter was highly increased in the plasma of hypophysectomized homografted rats. These animals showed also increased levels of plasma corticosterone. However, daily injection of corticosterone failed to promote somatic growth in hypophysectomized non-homografted rats. These results suggest that PRL, and not other hormonal factors, promotes somatic growth in hypophysectomized homografted rats, and stress the concept that only PRL is secreted in significant amounts by pituitary homografts.

Behavioral effects of perinatal administration of antidepressant drugs in the rat.

The monoamine reuptake blockers, imipramine, desipramine, and chlorimipramine, and the monoamine-oxidase inhibitors, iproniazid and isocarboxazid, were administered to pregnant rats (acutely at day 15 of pregnancy, or subchronically from day 10 of pregnancy to the delivery) or to newborn pups (from day 1 to day 5 of life). Prenatal acute injection of the antidepressant drugs failed to modify the development of neonatal reflexes of the rat pups and their adult behavior. Prenatal subchronic administration of the antidepressant drugs was followed by an increase in the number of pups showing neonatal reflexes, but also by an inhibition of the open field behavior and the acquisition of active avoidance responses tested in adulthood. In this respect, monoamine-oxidase inhibitors appeared to be more potent than monoamine reuptake blockers. Furthermore, neonatal administration of all the antidepressant drugs caused an inhibition of the acquisition of active avoidance responses tested in adulthood, but only the monoamine-oxidase inhibitor, isocarboxazid, significantly inhibited also the open field behavior of adult rats. Neither prenatal nor neonatal administration of the antidepressant drugs affected sexual activity of adult rats. The present results suggest that only a prolonged treatment with antidepressant drugs can affect neonatal or adult behavior of the rat, probably through an interference with central monoamine neurotransmission.

Phospholipid liposomes potentiate the inhibitory effect of antidepressant drugs on immobility of rats in a despair test (constrained swim).

Male rats forced to swim in a cylinder assumed an immobile posture. Immobility was reduced by antidepressant drugs, such as imipramine, desimipramine, iproniazid and mianserin injected 24, 5 and again 1 h prior to behavioral testing. Subchronic (4, 7 and 10 days) treatment with sonicated preparations of bovine hypothalamic phospholipid liposomes potentiated the inhibitory effect of all antidepressant drugs in the despair test. Acute administration of phospholipid liposomes failed to influence the drug effect. Furthermore, neither subchronic nor acute administration of phospholipid liposomes per se modified the immobility in the despair test. It is possible that the action of phospholipid liposomes on the inhibitory effect of antidepressant drugs on immobility of rats in the despair test may depend on potentiation of antidepressant-induced change in the sensitivity of monoamine receptors in the brain.

Neuroendocrine and behavioral effects of flunarizine in young and old rats.

Neuroendocrine and behavioral effects following an acute or chronic treatment with the calcium antagonist, flunarizine, have been studied in young and old rats. Both in young and old rats, acute administration of flunarizine (2 mg/kg) failed to modify plasma prolactin (PRL) levels, as measured at 8.00 a.m., 4.00 p.m. and 12.00 p.m. A chronic treatment with flunarizine (0.5 mg/kg/day, for 20 days) in young rats was followed by a relevant, albeit statistically not significant, increase in plasma PRL levels, as measured at 8.00 a.m. and 4.00 p.m., and by a significant decrease at 12.00 p.m. A shift of nocturnal peak of plasma PRL levels from 12.00 p.m. to 4.00 a.m. was observed in these animals. A chronic treatment with flunarizine in old rats was followed by a significant increase in plasma PRL levels, as measured at 12.00 p.m. The acquisition of active avoidance behavior was studied in a shuttle-box test. Acute administration of flunarizine failed to change the performance of young and old rats in acquiring the behavioral response, as measured by the total number of conditioned avoidance responses (CARs) and the percentage of learners. When flunarizine was administered chronically, a decrease in CARs and learners was observed both in young and old rats. This was accompanied by a significant increase in the percentage of animals that froze during the acquisition session. No significant effect was found in young and old rats tested in a "despair" test after a chronic treatment with flunarizine.

Prolactin inhibits the development of stress-induced ulcers in the rat.

Hyperprolactinaemia, as induced by pituitary homografts under the kidney capsule, was accompanied by an inhibition of development of gastric ulcers following the application of cold-plus-restraint stress in male rats. This effect was mimicked by intracisternal administration of a low dose of the hormone. Peripheral injection of the dopamine receptor antagonist, domperidone, also inhibited the development of stress-induced ulcers. However, no effect was found after peripheral injection of another dopamine receptor antagonist, haloperidol. This latter drug appeared to antagonize the cytoprotective effect of prolactin (PRL) on stress-induced ulcers. Furthermore, peripheral injection of the prostaglandin synthesis inhibitor, indomethacin, increased the incidence of gastric ulcers in hyperprolactinaemic rats subjected to cold -plus-restraint stress. These data suggest that the cytoprotective effect of PRL on development of gastric ulcers in stressed animals may involve both central (i.e. dopamine transmission) and peripheral (i.e. prostaglandin synthesis) mechanisms.

Behavioral effects of arginine in male rats.

The effects of aminoacid arginine on conditioned and unconditioned behavior were studied in male rats. Arginine was administered orally at different dose levels. Both acute and subchronic (7 days) treatment schedule was performed. Exploratory behavior of the rats was studied in an open field. Acquisition of active avoidance behavior was studied in the shuttle-box test situation, and retention of passive avoidance reaction was studied in a step-through type of passive avoidance behavior. Acute administration of arginine failed to affect the acquisition and the retention of avoidance responses, and exploratory behavior of the rats. A 7-day treatment with the aminoacid caused an increase in ambulation of rats of Wistar strain, and a facilitation of acquisition and retention of avoidance responses in rats of CDR strain with poor learning capacity. It is possible that behavioral effects or arginine depend on its involvement in nucleic acid synthesis.

Effects of mastectomy and vagotomy on grooming behavior of the rat: possible involvement of prolactin.

Surgical interventions such as unilateral mastectomy or vagotomy affect plasma prolactin (PRL) levels. Right-side mastectomized rats exhibiting high levels of plasma PRL showed increased grooming behavior. Left-side mastectomized rats with low levels of plasma PRL performed poor grooming activity. Bilateral mastectomy that caused a slight increase in plasma PRL levels was followed by enhanced grooming behavior. Both left and right vagotomy resulted in a significant increase in plasma PRL levels. However, only left-side vagotomized rats exhibited increased levels of grooming behavior, while no difference between right-side vagotomized rats and controls occurred. It is possible that changes in plasma PRL levels induced by surgical interventions affect grooming activity of the rat. However, the hypothesis that the integrity of peripheral organs is important for the display of grooming behavior cannot be ruled out.

Effects of valproic acid derivatives on the acquisition of active avoidance behavior in the rat.

The effects of valproic acid derivatives on the acquisition of active avoidance behavior have been studied in the rat. Sodium valproate (50 and 100 mg/kg), magnesium valproate (100 mg/kg) and dipropylacetamide (100 mg/kg) were administered intraperitoneally 1 hr prior to the behavioral test (shuttle-box, single session). Acquisition of active avoidance behavior was facilitated by sodium valproate, unaffected by magnesium valproate, and inhibited by dipropylacetamide. These findings suggest that behavioral effects of valproic acid derivatives cannot be explained only in terms of a general inhibitory action on the central nervous system.

Amphetamine-induced analgesia does not involve brain opioids.

The intrinsic analgesic properties of amphetamine were studied in rats. Subcutaneous injection of amphetamine exerted an additive effect on morphine-induced analgesia in the hot-plate test. Amphetamine itself showed intrinsic analgesic activity in a dose-dependent manner. Administration of naloxone failed to affect the analgesia induced by amphetamine. However, injection of haloperidol totally suppressed the amphetamine-induced change in pain response latency. Both naloxone and haloperidol failed to affect the pain threshold when injected alone, but inhibited morphine-induced analgesia. It is concluded that amphetamine possesses intrinsic analgesic properties which involve catecholamine but not opioid transmission in the brain.

Behavioral activity of a short chain ACTH analog.

The behavioral activity of ACTH1-17 analog (beta-Ala1, Lys17) ACTH1-17-4 -amino-n-butilamide (Ala1-Lys17-ACTH1-17) has been studied in the rat. Acquisition of shuttle-box active avoidance behavior was facilitated by Ala1-Lys17-ACTH1-17 administered both subcutaneously (SC) and intracerebroventricularly (ICV), and this effect was suppressed by peripheral administration of haloperidol or naltrexone. Extinction of pole jumping active avoidance behavior was delayed by SC administration of the peptide in a dose-dependent manner. Retention of a step-through passive avoidance behavior was facilitated SC or ICV injection of Ala1-Lys17-ACTH1-17. Adrenalectomy failed to modify the effects of the peptide on the retention of passive avoidance behavior. Furthermore, ICV injection of graded doses of Ala1-Lys17-ACTH1-17 induced excessive grooming, and this effect was totally prevented by intraperitoneal (IP) injection of haloperidol or naltrexone SC administration of Ala1-Lys17-ACTH1-17 induced a slight but significant increase in negative responses in a test for behavioral responsiveness to electrical footshock. This effect was totally prevented by IP injection of naltrexone. It is concluded that Ala-Lys17-ACTH1-17 shares some of the behavioral effects of ACTH4-10 and some ACTH1-24, but it seems to be more potent than the latter peptides. Both dopamine and opioid transmission seem to be involved in the behavioral activity of Ala1-Lys17-ACTH1-17.

Behavioral effects of phosphatidylserine after perinatal administration in rats.

Behavioral effects of the acidic phospholipid phosphatidylserine (PS) were studied in rats after perinatal (prenatal or neonatal) administration. PS was administered to pregnant rats from day 5 of pregnancy. PS liposomes were also injected i.p. to offspring from postnatal days 1-5. PS-treated rats showed a more precocious onset of neonatal behaviors, and a significant improvement in acquiring avoidance responses when tested at 60 days of age. Behavioral effects of PS may be related to a possible influence on dendritic arborization during perinatal period.