Effects of simultaneous exposure to stress and nicotine on nicotine-induced locomotor activation in adolescent and adult rats

Preclinical studies have shown that repeated stress experiences can result in an increase in the locomotor response to the subsequent administration of drugs of abuse, a phenomenon that has been termed behavioral cross-sensitization. Behavioral sensitization reflects neuroadaptive processes associated with drug addiction and drug-induced psychosis. Although cross-sensitization between stress- and drug-induced locomotor activity has been clearly demonstrated in adult rats, few studies have evaluated this phenomenon in adolescent rats. In the present study, we determined if the simultaneous exposure to stress and nicotine was capable of inducing behavioral sensitization to nicotine in adolescent and adult rats. To this end, adolescent (postnatal day (P) 28-37) and adult (P60-67) rats received nicotine (0.4 mg/kg, sc) or saline (0.9 percent NaCl, sc) and were immediately subjected to restraint stress for 2 h once a day for 7 days. The control group for stress was undisturbed following nicotine or saline injections. Three days after the last exposure to stress and nicotine, rats were challenged with a single dose of nicotine (0.4 mg/kg, sc) or saline and nicotine-induced locomotion was then recorded for 30 min. In adolescent rats, nicotine caused behavioral sensitization only in animals that were simultaneously exposed to stress, while in adult rats nicotine promoted sensitization independently of stress exposure. These findings demonstrate that adolescent rats are more vulnerable to the effects of stress on behavioral sensitization to nicotine than adult rats.

Repeated exposure of adolescent rats to oral methylphenidate does not induce behavioral sensitization or cross-sensitization to nicotine

Several lines of evidence indicate that the use of stimulant drugs, including methylphenidate (MPD), increases tobacco smoking. This has raised concerns that MPD use during adolescence could facilitate nicotine abuse. Preclinical studies have shown that repeated treatment with an addictive drug produces sensitization to that drug and usually cross-sensitization to other drugs. Behavioral sensitization has been implicated in the development of drug addiction. We examined whether repeated oral MPD administration during adolescence could induce behavioral sensitization to MPD and long-lasting cross-sensitization to nicotine. Adolescent male Wistar rats were treated orally with 10 mg/kg MPD or saline (SAL) from postnatal day (PND) 27 to 33. To evaluate behavioral sensitization to MPD in adolescent rats (PND 39), the SAL pretreated group was subdivided into two groups that received intragastric SAL (1.0 mL/kg) or MPD (10 mg/kg); MPD pretreated rats received MPD (10 mg/kg). Cross-sensitization was evaluated on PND 39 or PND 70 (adulthood). To this end, SAL- and MPD-pretreated groups received subcutaneous injections of SAL (1.0 mL/kg) or nicotine (0.4 mg/kg). All groups had 8 animals. Immediately after injections, locomotor activity was determined. The locomotor response to MPD challenge of MPD-pretreated rats was not significantly different from that of the SAL-pretreated group. Moreover, the locomotor response of MPD-pretreated rats to nicotine challenge was not significantly different from that of the SAL-pretreated group. This lack of sensitization and cross-sensitization suggests that MPD treatment during adolescence does not induce short- or long-term neuroadaptation in rats that could increase sensitivity to MPD or nicotine.

Frugivory in Lacistema hasslerianum Chodat (Lacistemaceae), a gallery forest understory treelet in Central Brazil / Frugivoria em Lacistema hasslerianum Chodat (Lacistemaceae), uma arvoreta de subbosque de Mata de Galeria no Brasil Central

The objectives of this study were to know and to characterize the behavioural patterns of frugivorous birds in Lacistema hasslerianum. The study was carried out in the Panga Ecological Station (Uberlândia, Minas Gerais State). During the frutification time (September-October), L. hasslerianum was observed for 31.25 hours and received 58 visits by five species of birds. Tyrannidae was the best represented family (2 species). Pipridae was the most frequent visitor in L. hasslerianum (68.97 percent of visits). The number of consumed fruits was correlated with the time of permanence on the plant. The main foraging tactic was "Stalling" (58.62 percent) and the most frequent fruit consumption strategy was "swallower" (45.25 percent), which indicates a high seed dispersal potential. Antilophia galeata (Pipridae), although a territorial bird, presented the best dispersal efficiency for Lacistema hasslerianum, because of its consumption rate (2.82 whole fruits consumed/minute).

Os objetivos deste estudo foram conhecer e caracterizar o padrão comportamental das aves frugívoras em Lacistema hasslerianum. O estudo foi realizado na Estação Ecológica do Panga (Uberlândia-MG). Durante a época de frutificação (setembro-outubro), L. hasslerianum foi observada por 31 horas e 15 minutos e recebeu 58 visitas de cinco espécies de aves. Tyrannidae foi a família mais representativa (2 espécies), Pipridae, a família mais frequente (68,97 por cento). O número de frutos consumidos foi correlacionado com o tempo de permanência na planta. A principal tática de forrageamento utilizada pelos visitantes de L. hasslerianum foi "vôo" (58,62 por cento) e a estratégia de consumo do fruto predominante foi "engolidor" (45,25 por cento), o que indica um elevado potencial de dispersão. Antilophia galeata (Pipridae), apesar de territorialista, apresentou a maior eficiência de dispersão para L. hasslerianum devido à sua taxa de consumo (2,82 frutos consumidos inteiros/minuto).

Frugivory and dispersal of Faramea cyanea (Rubiaceae) in Cerrado woody plant formations

The objective of this study was to observe and compare the community of birds that utilize the tree species Faramea cyanea, in contiguous areas of cerradäo and gallery forest, and also to characterize the behavioral patterns of the birds. The study was carried out in the Panga Ecological Station (Uberlândia, Minas Gerais State), in April and May 2001. Nine individuals of F. cyanea were observed in periods between 06:45-11:30 h for a total of 44.5 hours. There were 204 visits by 13 bird species. Tyrannidae was the most represented family (five species) and Turdidae, the most frequent (72.1 percent of visits). The number of consumed fruits was correlated with the permanence time on the plant. There was no significant difference between the two forests habitats, in terms of foraging tactics or fruit consumption strategies. In spite of the predominance of omnivorous birds (89.5 percent) in both habitats, the swallower strategy (84.2 percent) indicates high seed dispersal potential. Antilophia galeata, a frugivorous bird, presented the greatest rate of consumed fruits per minute in both gallery forest (2.15) and cerradäo (1.06)