Reserpine enhances amphetamine stereotypies without increasing amphetamine-induced changes in striatal dialysate dopamine

Indirect evidence suggests that amphetamine (AMPH) releases dopamine (DA) from an extravesicular, cytoplasmic pool. Disruption of vesicular DA storage by reserpine has been hypothesized to increase the concentration of extravesicular DA available for release by AMPH, which is consistent with the observation that reserpine does not prevent but augments the behavioral response to AMPH. In order to more directly test this hypothesis, the in vivo microdialysis technique was used to concurrently examine the behavioral and striatal dopaminergic response to AMPH (1.25 or 2.5 mg/kg) 24 h following reserpine pretreatment (2.5 mg/kg). Reserpine decreased tissue levels of DA by approximately 90% and reduced baseline dialysate DA concentrations by approximately 80%. Reserpine augmented the behavioural effects of AMPH, particularly increasing the occurrence and intensity of stereotypies. In contrast, reserpine did not alter the amount or duration of AMPH-induced DA release. This observation confirms that DA release by AMPH does not depend on vesicular stores but is inconsistent with the hypothesis that augmentation or behaviour by reserpine results from increased striatal DA release.     

Co-localization of SCPB-like and FMRFamide-like immunoreactivities in crustacean nervous systems

A monoclonal antibody to the molluscan small cardioactive peptide SCPB and a polyclonal antibody to FMRFamide were used to localize antigens in the stomatogastric nervous system and brain of two species of Cancer. Both antibodies labeled cell bodies, axons, and neuropilar processes in the brain and in the stomatogastric nervous system. All of the SCPB immunoreactive neurons were co-labeled with antibody to FMRFamide. However, antibody to FMRFamide labeled additional neurons of the commissural ganglion and the brain that were not immunoreactive to the monoclonal SCPB antibody.     

Differential loss of neuromuscular connections according to activity level and spinal position of neonatal rabbit soleus motor neurons

We have tested whether the ability of synapses to compete for occupancy of endplates during neuromuscular synapse elimination is affected by differences in the spinal position or in the activity level of the parent motor neuron. To test the role of spinal position, the relative sizes of motor units for motor neurons from middle and extreme (rostral/caudal) positions in the rabbit soleus motor pool were determined at 3 postnatal ages: 4-5 d ("early" ages, when the soleus is heavily polyinnervated), 8-9 d ("intermediate"), and 11-15 d ("late," when the soleus has just reached singly innervated state). Average motor unit sizes from extreme ventral roots were similar to those from middle ventral roots in early-aged soleus muscles but were significantly smaller (by 18-27%) for both intermediate and late muscles. Thus, motor neurons from extreme positions evidently compete less effectively for retention of synapses than those from middle positions. To test the role of differential activity, inactive and active synapses were pitted directly against one another by implanting Silastic plugs laden with tetrodotoxin (TTX) into one of the spinal nerves containing a minority of the soleus motor axons. Differential activity was maintained during a period of extensive synapse loss, from the time of the implant at day 4 or 5 until the intermediate age (day 8-9). Motor unit twitch tensions were subsequently measured to determine the relative number of synapses retained by individual active and inactive motor neurons. The inactivated motor units were on average significantly larger (by more than 50%) than the corresponding group from normal and control-implanted animals. The abnormally large size of inactivated motor units persisted in animals allowed to recover from the TTX block and examined after multiple innervation had disappeared. Hence, the effect of the TTX block cannot be attributed to a simple slowing of synapse elimination specifically among the inactive motor neurons. We conclude that complete presynaptic inactivity improves the chances of survival relative to that for normal activity during synapse elimination in the neonatal rabbit soleus muscle. This difference in competitive ability may contribute to the development of an important characteristic of adult muscles, the correlation between motor unit size and recruitment threshold.     

The effects of clonidine and yohimbine on human information processing

The effects of clonidine and yohimbine on human information processing were tested in six normal volunteers ages 18–30 years. Subjects were tested in a pre-post design with sessions conducted at weekly intervals. Three drug conditions were: Placebo (lactose), 0.2 mg clonidine, and 30 mg yohimbine. Two choice reaction time (RT) tasks were used. One was a stimulus evaluation-response selection task (SERS) that has been shown to be sensitive tod-amphetamine, methylphenidate and scopolamine. The other task was to assess stimulus pre-processing and used spatial frequency as a discriminative stimulus. The principle finding was that clonidine slowed RT; this effect was significant for both tasks. In contrast, yohimbine tended to speed RT, but the effects were significant only for the spatial frequency task on some analyses while not for others. RTs to high spatial frequency stimuli were speeded more than for low spatial frequency. The effects of these two NE drugs were compared with findings withd-amphetamine and scopolamine and interpreted within the framework of a serial information processing model proposed by Callaway (1983). Specifically, it is suggested that yohimbine and clonidine affect an early pre-processing stage.     

HLA typing used with cultured amniotic and chorionic villus cells for early prenatal diagnosis or parentage testing without one parent's availability

Like fetal fibroblasts and amniotic fluid cells, cultured chorionic villus cells can also be HLA typed with selected typing sera after preincubation with gamma interferon to promote better antigen expression. A modified procedure now in use would also allow any of these cell types to be tested for the presence or absence of all known HLA A,B,C, and DR antigens with standard preplated typing trays. This procedure was used to confirm that an on-going pregnancy had resulted from the successful in vitro fertilization and implantation of an anonymous donor's ovum and could also be of major use in rape or artificial insemination cases when the identity of the possible father(s) is not known.     

Removal of GABAergic inhibition alters subthreshold input in neurons in forepaw barrel subfield (FBS) in rat first somatosensory cortex (SI) after digit stimulation

Our objective was to test the hypothesis that suppression of GABAergic inhibition results in an enhancement of responses to stimulation of the surround receptive field. Neurons in the forepaw barrel subfield (FBS) in rat first somatosensory cortex (SI) receive short latency suprathreshold input from a principal location on the forepaw and longer latency subthreshold input from surrounding forepaw skin regions. Input from principal and surround receptive field sites was examined before, during, and after administration of the GABA(A) receptor blocker bicuculline methiodide (BMI) (in 165 mM NaCl at pH 3.3-3.5). In vivo extracellular recording was used to first identify the location of the glabrous forepaw digit representation within the FBS. In vivo intracellular recording and labeling techniques were then used to impale single FBS neurons in layer IV as well as neurons in layers III and V, determine the receptive field of the cell, and fill the cell with biocytin for subsequent morphological identification. The intracellular recording electrode was fastened with dental wax to a double-barrel pipette for BMI iontophoresis and current balance. A stimulating probe, placed on the glabrous forepaw skin surface, was used to identify principal and surround components of the receptive field. Once a cell was impaled and a stable recording was obtained, a stimulating probe was placed at a selected site within the surround receptive field. Single-pulse stimulation (1 Hz) was then delivered through the skin probe and the percentage of spikes occurring in 1-min intervals before BMI onset was used as a baseline measure. BMI was then iontophoresed while the periphery was simultaneously stimulated, and spike percentage measured during and after BMI ejection was compared with the pre-BMI baseline. The major findings are: (1) suppression of GABAergic inhibition enhanced evoked responses to firing level from sites in surround receptive fields in 65% of the cells ( n=17); (2) evoked responses were rapidly elevated (within 1 min) to suprathreshold firing in the presence of BMI in 31% of the cells; (3) GABAergic inhibition was reversible [suprathreshold spiking gradually reversed to subthreshold excitatory postsynaptic potentials (EPSPs) in 45% of the cells tested]; (4) BMI altered the stimulus-evoked and non-stimulus-evoked firing pattern in SI neurons from single spikes to burst patterns in all tested cells; and (5) iontophoresis of NaCl (165 mM) without BMI was ineffective in altering evoked responses in control cells ( n=4). The present findings support the notion that subthreshold input from surround receptive fields is one possible mechanism for rapid cortical reorganization in barrel cortex and that GABAergic inhibition may regulate its expression. Possible corticocortical and thalamocortical substrates for subthreshold input to reach barrel neurons are discussed.     

Evaluation of the Du Pont HERPCHEK herpes simplex virus antigen test with clinical specimens.

The HERPCHEK herpes simplex virus (HSV) antigen test (Du Pont, Billerica, Mass.) is a biotinstreptavidin-amplified enzyme-linked immunoassay for the detection of HSV antigen directly in clinical specimens. In a total of 200 mucocutaneous specimens, predominantly lesions from nongenital sites, HERPCHEK had a sensitivity of 90% and a specificity of 99% compared with the shell vial tissue culture method which uses primary rabbit kidney cells. Five false-negative results by HERPCHEK were found with specimens that contained a low percentage of positive cells by the direct immunoperoxidase stain used in a tissue culture method (1 to 9%). The absorbance values of the clinical specimens by the HERPCHEK test do not correlate well with the percentage of positive cells. Our results indicate that the HERPCHEK HSV antigen test, when performed with specimens from lesions, is a sensitive and specific test as compared with shell vial culture.