Effects of BNST lesions in female rats on forced swimming and navigational learning.

The bed nucleus of the stria terminalis (BNST) in the forebrain shows sexual dimorphism in its neuroanatomical connectivity and neurochemical characteristics. The structure is involved in many behavioral and motivational phenomena particularly related to coping with stress. Female rats differ from males in responding to stressful situations such as forced swimming and navigational learning in the water maze. It was previously shown that bilateral damage to the BNST in male Wistar rats aggravated depression as measured by forced swim tests, but did not impair navigational learning in the water maze. The present study extended the findings to female rats demonstrating that bilateral electrolytic lesions of the BNST increased immobility and decreased climbing compared to sham-operated controls, but failed to affect performance in the water maze. Additionally, lesions did not alter behavior in the open field and the elevated plus-maze tests suggesting not only that the modulation of depression by BNST lesions is specific, but also providing support for the view that the BNST may not necessarily be critically involved in anxiety.

BNST lesions aggravate behavioral despair but do not impair navigational learning in rats.

The bed nucleus of the stria terminalis (BNST) is a basal forebrain structure involved in many motivational processes closely linked to stress regulation. The present study investigated the effect of bilateral lesions of the BNST in male Wistar rats on behavioral despair and navigational learning in the Morris water maze both of which present stressful challenges. Compared to controls, BNST-lesioned animals displayed longer duration of immobility in the second of two forced swim tests used to assess behavioral despair but performed similarly in the water maze task. The present results indicate strongly that the BNST is involved in the modulation of behavioral despair. Experimentally induced depression by BNST lesions does not impair learning and memory in the water maze suggesting a possible dissociation between BNST-mediated depression and cognitive performance.

Effect of lesioning the suprachiasmatic nuclei on behavioral despair in rats.

The suprachiasmatic nucleus (SCN) is involved in regulating many biological rhythms. Several lines of research implicate the SCN in affective behavior. The SCN is directly involved in regulating the daily rhythms of the hypothalamo-pituitary-adrenal (HPA) axis hormones involved in stress. Bilateral lesions of the SCN disrupt both the rhythms and the basal levels of the HPA axis hormones involved in coping with stress. Moreover, stress can affect the biological rhythms regulated by the SCN, and disruption of biological rhythms in turn can cause stress. The present study assessed the effect of bilateral destruction of the SCN on behavioral despair, an animal model of depression sensitive to antidepressant treatment. The results indicate that bilateral destruction of the SCN results in reduced immobility in the second forced swimming test (FST) compared to sham controls and animals with incomplete lesions. These results indicate that bilateral destruction of the SCN has a protective effect in the induction of behavioral despair which may arise out of disruption of the secretion of the HPA axis hormones and/or of the neural connections between the SCN and the limbic structures that modulate the response to swim stress.

A single day of constant light (L/L) provides immunity to behavioral despair in female rats maintained on an L/D cycle.

The present experiment investigated the potentially ameliorative effect of exposure to light in the dark phase of an 12:12 h daily lighting schedule (12L/12D cycle) on behavioral despair, an animal model of depression based on two forced swim tests separated by 24 h. Experimental groups of female Wistar rats were maintained on the 12L/12D cycle except for a single exposure to 12 h of light treatment in the dark phase of the 12L/12D cycle. Control animals were treated similarly except for light treatment. Animals then underwent one of two sets of behavioral tests starting on either the day light (or control) treatment ended (No Delay groups) or 24 h thereafter (Delay groups). The treatment for subgroups of light-treated and control animals tested with or without delay consisted of either two forced swim tests separated by 24 h or testing in the open field and elevated plus maze. Results indicated that a single exposure to a 12-h light treatment has protective effect on behavioral despair in groups tested with or without delay as measured by shorter duration of immobility in the second swim test compared to the controls. Light-treated and control animals behaved similarly in the open field and elevated plus-maze tests.

The 980-nm diode laser for brain surgery: histopathology and recovery period.

The 980-nm diode laser has been under investigation for neurosurgery because of a local peak in the absorption spectra of water around this wavelength. This work was carried out to examine the extent of thermal changes and the recovery process of laser-induced brain lesions. In order to study the quality of the lesions, a conventional monopolar electrocoagulation technique was applied comparatively. An in vivo stereotaxic neurosurgical procedure was performed on Wistar rats. Bilateral brain lesions of the same size (2-3 mm diameter) were created with a diode laser and via electrocoagulation. Subjects were sacrificed 0, 2 and 7 days after surgery in order to observe the healing process of the necrotic tissue. The surgical after-effects of both types of lesions were identified through immunohistochemical staining with CD68 macrophage marker and haematoxylin eosin (H&E). CD68 was found to be more efficient than H&E in determining the thermally altered areas. Histological examinations showed that the 980-nm diode laser system has a remarkable ablating ability with minimal thermal damage of nearby tissue.