Granule cells in the ventral, but not dorsal, dentate gyrus are essential for kainic acid-induced wet dog shakes.

Intrahippocampal injections of colchicine selectively destroy dentate granule cells. Wet dog shaking elicited by systemic administration of kainic acid is eliminated by bilateral destruction of ventral dentate granule cells but unaffected by bilateral destruction of dorsal dentate granule cells. This implies that ventral dentate granule cells are essential for the generation of kainic acid-induced wet dog shakes.

Granule cells in the ventral dentate gyrus are essential for kainic acid-induced wet dog shakes but not those induced by precipitated abstinence in morphine-dependent rats.

Wet dog shaking elicited by systemic administration of kainic acid is eliminated by bilateral destruction of ventral dentate granule cells. In contrast, wet dog shaking induced by naltrexone precipitated abstinence in morphine-dependent rats is unaffected by destruction of ventral dentate granule cells. It is concluded that at least two anatomically distinct brain regions modulate wet dog shaking behavior.

Diethyldithiocarbamate and dithizone augment the toxicity of kainic acid.

Male Fischer-344 rats were injected i.p. with diethyldithiocarbamate or dithizone 15 min after kainic acid (KA), s.c. Diethyldithiocarbamate and dithizone reduced both the number of wet dog shakes and the latency to onset of seizures induced by KA. Moreover, they increased the severity of seizures. These compounds may be useful tools for investigating the role of zinc in central nervous system excitatory transmission and/or convulsive phenomena.

Administration of kainic acid and colchicine alters mu and lambda opiate binding in rat hippocampus.

Quantitative in vitro autoradiography was used to assess the effects of kainic acid (KA) and colchicine (COL) on mu and lambda opiate binding in the rat hippocampus. Rats were treated with either systemic KA, a neurotoxin that damages CA3 pyramidal cells and causes seizures and wet-dog shakes, or intrahippocampal COL to destroy dentate granule cells and their mossy fibers, or both toxins. Moderate levels of mu binding were detected in the pyramidal layer and in the stratum lacunosum-moleculare; binding was greater in the ventral hippocampus. Levels of mu binding were markedly increased in all regions 48 h after treatment with KA. Two weeks after COL treatment, there was a modest decrease in mu binding; COL plus KA gave results similar to COL alone. Dense lambda binding was present over the mossy fibers in the stratum lucidum, but was absent over the pyramidal layer. In contrast to mu binding, lambda binding was greater in the dorsal hippocampus. KA alone had little effect on lambda binding, whereas COL alone caused large decreases. KA plus COL caused even larger decreases in lambda binding, to as much as 85% below control. These results demonstrate that mu and lambda binding are localized to different parts of the hippocampus, respond differently to neurotoxin lesions, and likely serve different roles in this brain region. The number of mu sites is responsive to the release of enkephalin; these receptors appear to be linked to opiate-induced hippocampal seizure activity, especially wet-dog shakes. Lambda sites may serve as autoreceptors on mossy fibers.

Assessment of neuromedin B polyclonal antibodies as molecular probes in neural tissue.

Five unique, high affinity rabbit polyclonal antibodies against neuromedin B were characterized in a radioimmunoassay in terms of the following parameters: pH and type of buffer, ionic strength, and non-ionic detergents in order to optimize immunoglobulin-peptide interaction; specificity using peptides of the bombesin family, in addition to the tachykinin substance P; and affinity to neuromedin B. Optimum conditions included acidic pH (5.25), high ionic strength (greater than 0.1 M) and absence of non-ionic detergents, which inhibited the assay. Affinities for the 5 antibodies ranged from 10 to 48 fmol neuromedin B with titers from 1:1,000 to 1:10,000 and the sequence-specificity covered the entire peptide; cross-reactivity towards substance P was negligible. As a model tissue, rat spinal cord was homogenized with 5 different extraction solvents, including acetone, methanol, acid and alkaline conditions, and assayed by each polyclonal antiserum; neuromedin B immunoreactivity levels were highest in acid and alkaline extracts and reflected the specificity of the antibody used. Applying these antisera to rat brain extracts, the posterior pituitary gland contained the highest concentration of immunoreactive equivalents of neuromedin B followed by the anterior pituitary, hypothalamus, and hippocampus. The immunoreactive content in the pituitary and hypothalamus, however, depended on the particular antisera used with significant (P less than 0.01) differences existing between them. Further application of these polyclonal antibodies to a spinal cord extract analyzed by isocratic reverse-phase HPLC conditions also revealed differences in their cross-reactivity with the immunoreactive peptides. These antisera may now be used as molecular probes for the determination of extractable immunoreactive neuromedin B from neural tissue and in situ localization by immunohistochemical techniques.

Unrecognized errors due to analog filtering of the brain-stem auditory evoked response.

Analog filtering of the brain-stem auditory evoked response (BAER) and synthetic wave forms using steeply sloped filters are shown to produce significant distortion even when filter cut-off frequencies are well removed from the wave form spectrum. The degree of distortion is such that it may result in erroneous identification of peaks in the BAER. Reversal of the order of peaks may occur with high pass settings at only 1/4 the lowest constituent frequency. Filter effects were identified as a major source of cross-laboratory differences in BAERs recorded from laboratory rats. Filter transfer functions of a typical analog filter set were derived for both gain and phase as a function of frequency. Filtering of synthetic wave forms was used to elucidate and highlight distortion effects. A typical Long-Evans rat BAER wave form was spectrum analyzed and conclusions were drawn with respect to appropriate bandpass frequencies.