Foot shock facilitates reward seeking in an experience-dependent manner.

Animals organize reward seeking around aversive events. An abundance of research shows that foot shock, as well as a shock-associated cue, can elicit freezing and suppress reward seeking. Yet, there is evidence that experience can flip the effect of foot shock to facilitate reward seeking. Here we examined cue suppression, foot shock suppression and foot shock facilitation of reward seeking in a single behavioural setting. Male Long Evans rats received fear discrimination consisting of danger, uncertainty, and safety cues. Discrimination took place over a baseline of rewarded nose poking. With limited experience (1-2 sessions), all cues and foot shock suppressed reward seeking. With continued experience (10-16 sessions), suppression became specific to shock-associated cues, foot shock briefly suppressed, then facilitated reward seeking. Our results provide a means of assessing positive properties of foot shock, and may provide insight into maladaptive behaviour around aversive events.

Targeting Corticotropin-Releasing Factor Projections from the Oval Nucleus of the Bed Nucleus of the Stria Terminalis Using Cell-Type Specific Neuronal Tracing Studies in Mouse and Rat Brain.

The bed nucleus of the stria terminalis (BNST) is known to play a critical role in mediating the behavioural and autonomic responses to stressors. The oval nucleus of the BNST (BNSTov) contains cell bodies that synthesise the stress hormone corticotropin-releasing factor (CRF). Although afferent fibres originating from the BNSTov have been shown to innervate several key structures of the neuroendocrine and central autonomic system, the question remains as to whether some of these fibres are CRF-positive. To directly address this question, we injected a 'floxed' anterograde tracer (rAAV5/EF1a-DIO-mCherry) into the BNSTov of CRFp3.0CreGFP transgenic mice, which express a green fluorescent protein (GFP) under the control of the CRF promoter. Serial sections were then analysed for the presence of double-labelled fibres in potential projection sites. To determine whether CRF neurons in the rat BNSTov send comparable projections, we infused rat BNSTov with an adeno-associated viral vector (AAV) in which the human synapsin promoter drives enhanced GFP expression. We then used CRF immunoreactivity to examine double-labelled fluorescent fibres and axon terminals in projection sites from brain sections of the AAV-infused rats. We have observed several terminal fields in the mouse and rat brain with double-labelled fibres in the Dorsal raphe nucleus (DRD), the paraventricular nucleus of the hypothalamus and, to a lesser extent, in the ventral tegmental area. We found double-labelled terminal boutons in the nucleus accumbens shell, prelimbic cortex and posterior basolateral nucleus of the amygdala. The most intense double-labelling was found in midbrain, including substantia nigra pars compacta, red nucleus, periaqueductal grey and pontine nuclei, as well as DRD. The results of the present study indicate that CRF neurons are the output neurons of the BNSTov and they send projections not only to the centres of neuroendocrine and autonomic regulation, but also regions modulating reward and motivation, vigilance and motor function, as well as affective behaviour.

Temporomandibular joint: computed tomographic three-dimensional reconstruction.

Computed tomography represents an effective and highly automated method to display biomedical data from many sources. It has a number of advantages over previous reconstruction methods, particularly the ability to automatically locate object-boundary outlines and produce shaded three-dimensional images of reconstructed data. A three-dimensional reconstruction of the temporomandibular joint was performed successfully on five cadaver heads using the Phillips Tomoscan and IP5000 image processor. The program used in this study of the temporomandibular joint is divided into five distinct steps: data gathering, rotation and projection, filtering, smoothing, and shading. Comparison of this type of data is important in the study of the normal and abnormal anatomy of the temporomandibular joint. Similarly, quantitative data obtained from reconstructed computed tomograms can be used to study normal anatomy in vivo and to examine the effects of various treatment modalities on the size and morphologic characteristics of tumors and other pathologic entities.