The present study aimed to characterize the phenomenon of behavioral sensitization to cocaine and to identify neuroanatomical structures involved in the induction and expression phases of this phenomenon. For this, in experiment 1 (induction phase), mice were treated with saline or cocaine every second day for 15 days (conditioning period), in the open-field or in their home-cages. In experiment 2 (expression phase), the same protocol was followed, except that after the conditioning period the animals were not manipulated for 10 days, and after this interval, animals were challenged with cocaine. Neuroanatomical structures involved in the induction and expression phases were identified by stereological quantification of c-Fos staining in the dorsomedial prefrontal cortex (dmPFC), nucleus accumbens core (NAc core and shell (NAc shell), basolateral amygdala (BLA), and ventral tegmental area (VTA). Neuroanatomical analysis indicated that in the induction phase, cocaine-conditioned animals had higher expression of c-Fos in the dmPFC, NAc core, BLA, and VTA, whereas in the expression phase, almost all areas had higher expression except for the VTA. Therefore, environmental context plays a major role in the induction and expression of behavioral sensitization, although not all structures that compose the mesolimbic system contribute to this phenomenon.

Males of Proechimys guyannensis, a rodent living in the Amazon rainforest are studied in biomedical research because of their antiepileptogenic mechanism. Females are usually taken from experimental designs, because of limited data of this sex. This study aimed to characterize the estrous cycle to include females together with males in research in a more balanced approach. The estrous cycle of P. guyannensis based through exfoliative cytology, determination of the vaginal occlusion membrane state, and hormonal analysis. In this study, cytological analyses of vaginal smears were performed for three months, three times a day. The observed length of the estrous cycle was 247 ± 81 h (mean ± SD) with a reproductive phase of 27.08 ± 17.39 h (estrus stage). We observed a frequent presence of both the open and closed states of the vaginal membrane in the estrus stage (fertile period) although only the open stage is a prerequisite for successful copulation. High levels of progesterone and estradiol were detected in proestrus. Levels of follicle-stimulating hormone peaked at the estrus stage. These data will establish the parameters and subsidies to set the grounds for future research either for investigating the biology of this species or to use P. guyannensis in research that previously excluded females. Information regarding female Proechimys is relevant to not only describe the species but also explain the interaction between sex hormones and physiological responses. Moreover, the present results will enhance rigor and reproducibility in preclinical studies. In conclusion, P. guyannensis reproductive cycles can occur spontaneously and cyclically independent of mating stimulation and the high levels of FSH in the estrus stage, suggest that ovulation occurs in the late phase of the estrus.

In addition to the classic motor symptoms of Parkinson’s disease (PD), patients also present with non-motor symptoms, such as autonomic dysfunction, which is present in almost 90% of patients with PD, affecting the quality of life and mortality. ...

Traumatic brain injury (TBI) is a major global health concern. The lateral fluid percussion injury (LFPI) model, widely used in rodents to simulate nonpenetrating TBI, has limited translational applicability due to anatomical differences between rodent and human brains. The common marmoset (Callithrix jacchus), a New World primate with a quasi-gyrencephalic brain, offers a promising alternative. This study aimed to standardize the LFPI model in marmosets by comparing trauma responses across parietal and temporal lobes. Ten adult marmosets underwent LFPI in these regions. Lesion volume was measured using Nissl staining; astrocytic and microglial responses were assessed via GFAP and Iba-1 immunofluorescence, and degenerating neurons were identified with Fluoro-Jade B. Righting reflex time and hemorrhage presence were evaluated as injury markers. Percussion aiming at the temporal lobe injury resulted in the most prominent lesions, epidural and subdural hematomas, and significant neuronal degeneration. Astrocytes showed longer processes after temporal trauma in the cortex and fewer branches in the hippocampal region CA1 than in the naive group. In contrast, hippocampal microglia showed fewer elongated branches in CA1 and dentate gyrus (DG), indicative of a reactive phenotype. Our results highlighted region-specific vulnerability, with temporal injury triggering the most pronounced inflammatory and degenerative responses. The marmoset LFPI model effectively mirrored key aspects of human TBI, supporting its translational relevance.

The Amazon rodent Proechimys guyannensis is widely studied for hosting various pathogens, though rarely getting sick. Previous studies on male Proechimys have revealed an endogenous resistance to epilepsy. Here, we assess in female Proechimys, whether sex hormones and biochemical aspects can interfere with the induction of status epilepticus (SE). The lithium-pilocarpine ramp-up protocol was used to induce SE, and blood sera were collected at 30 and 90 min after SE, alongside brains, for biochemical, western blot and immunohistochemical analyses. Results from non-ovariectomised (NOVX) Proechimys were compared to ovariectomised (OVX) animals. Data from female Wistars were used as a positive control of SE inductions. SE latency was similar in NOVX, OVX, and female Wistars groups. However, the pilocarpine dose required to induce SE in Proechimys was higher (25- to 50-folds more). Despite a higher dose, Proechimys did not show strong SE like Wistars; they only reached stage 2 of the Racine scale. These data suggest that female Proechimys are resistant to SE induction. Glucose and progesterone levels increased at 30 min and returned to normal at 90 min after SE. A relevant fact because in humans and rodents, SE leads to hypoglycaemia after 30 min of SE and does not return to normal levels in a short time, a typical adverse effect of SE. In OVX animals, a decrease in GABAergic receptors within 90 min of SE may suggest that ovariectomy produces changes in the hippocampus, including a certain vulnerability to seizures. We speculate that progesterone and glucose increases form part of the compensatory mechanisms that provide resistance in Proechimys against SE induction.