A spring loaded carrier for transection of fornix and other large fiber bundles

A comparison of taste reactivity changes induced by ventromedial hypothalamic lesions and stria terminalis transections

A hyperreactivity to the sensory qualities of a food, i.e., finickiness, is a defining feature of the ventromedial hypothalamic (VMH) lesion syndrome. The precise anatomical locus mediating this disturbance has not been determined. This study examines the hypothesis that interruption of amygdalo-hypothalamic connections (either ascending or descending) via the stria terminalis (ST) is involved in VMH lesion-induced finickiness. Taste reactivity was assessed in animals with VMH lesions, ST knife cuts, combined VMH/ST damage, and controls. In sham feeding tests of taste reactivity, ST and VMH rats were equally hyperreactive compared to controls. Rats with combined VMH and ST damage, however, were more reactive than both these groups. None of the brain lesions resulted in an overreactivity to quinine adulteration of the diet. In contrast to sham feeding, ST rats were not hyperphagic when feeding normally, although VMH rats were. In fact, ST damage attenuated VMH-induced hyperphagia and weight gain. We conclude that the taste reactivity changes induced by VMH lesions and ST transections are independent and additive indicating that VMH finickiness does not involve disruption of amygdalo-hypothalamic connections. Nonetheless, disruption of the ST produces a dramatic change in taste reactivity and the properties and origins of this disturbance are discussed.

A simpler retractable wire knife

A detailed description is presented for the construction of a simple and inexpensive retractable wire knife and holder/adjuster for stereotaxically placed transections of neural pathways. The accuracy and reliability of the knife are supported by experimental data demonstrating the ability of bilateral parasagittal hypothalamic knife cuts to induce excessive food intake and body weight gain in female rats.

Effects of hypothalamic knife cuts on feeding induced by paraventricular norepinephrine injections

The relationship between the fiber systems involved in the hypothalamic noradrenergic feeding response and the medial hypothalamic (MH) hyperphagia syndrome was appraised in male rats using knife cuts. Parasagittal knife cuts in the perifornical hypothalamus produced hyperphagia and excessive weight gain but failed to disrupt feeding in response to paraventricular hypothalamic injections of norepinephrine (NE). Coronal knife cuts in the posterior hypothalamus which extended from the midline to the lateral perifornical region also failed to disrupt NE feeding. These findings indicate that the output of the noradrenergic feeding system does not follow the feeding pathway implicated in the MH hyperphagia syndrome. They also suggest that the output of the noradrenergic feeding system is not directed laterally beyond the level of the fornix nor caudally into the lower brainstem over the medial forebrain bundle.

A retracting wire knife for cutting fiber bundles and making sheet lesions of brain tissue

A retracting knife which has two cutting wires for the transection of fiber bundles is described. The knife holds the fiber bundles of the stria terminalis between the two cutting wires and transects them by a shearing movement as the wires close. In addition, the feasability of such a knife producing a sheet lesion around the n. caudatus is also described.