Automatic temperature controller for maintaining body temperature in experimental animals

Striatal modulation of the jaw opening reflex

The effect of striatal electrical and chemical conditioning stimulation (L-glutamate 80-160 nmoles/0.5 microl) on the jaw opening reflex (JOR) was studied in Sprague-Dawley male rats anesthetized with urethane. The JOR was evoked by stimulation of the tooth pulp of lower incisors. This response was suppressed by transection of the dental root, which indicates according with the bibliography, a specific activation of the pulp nerves. Three type of responses were obtained on the evoked JOR by conditioning stimulation of the striatum; being the main one the suppression of the reflex elicited by tooth pulp activation. A second type of response was an increase of the tooth-JOR amplitude. This effect was observed more frequently with glutamate stimulation rather than with electrical activation of the striatum. A third response was observed with chemical stimulation but not by electrical stimulation of the striatum. This was a triphasic response which consisted in an increase followed by an inhibition and a late increase of the tooth-JOR amplitude. A biphasic effect, an increase prior to a decrease of the JOR amplitude, was also recorded with a minor frequency. The distribution of effective sites for electrical and chemical stimulation within the striatum are mainly similar located in the rostral aspect of the nucleus, with the inhibitory sites in the middle of the nucleus and intermingled with the excitatory ones. The complex responses (tri/biphasic) were observed ventrally and caudally in the nucleus. On the basis of the results mentioned above, one could assume that the striatum is related to the modulation of the JOR evoked probably by nociceptive stimulation. However, activation of other type of fibers could not be ruled out.

Substantia nigra pars reticulata single unit activity in normal and 60HDA-lesioned rats: effects of intrastriatal apomorphine and subthalamic lesions

The spontaneous activity and the response to intrastriatal application of apomorphine of substantia nigra pars reticulata (SNpr) single units was studied in four experimental groups of rats: (1) normal rats; (2) subthalamic nucleus (STN) lesioned rats; (3) rats bearing a 6-hydroxydopamine (60HDA) lesion; and (4) 60HDA-lesioned animals with an additional STN lesion. Thirty-eight percent of units from 60HDA-lesioned rats showed a bursting pattern of spontaneous activity, which was never found in normal rats. STN lesions had no effect on the spontaneous activity of SNpr units from normal rats, but reduced the percentage of burst units in 60HDA-lesioned animals. Intrastriatal apomorphine produced responses in 62% of SNpr units from normal rats and 85% of units from 60HDA-lesioned animals (P < 0.05). In addition, the modifications in the firing rate and in the coefficient of variation of the interspike intervals induced by intrastriatal apomorphine were significantly greater for the units isolated from 60HDA-lesioned rats. In particular, it was noted that all the burst units responded to apomorphine, showing the highest changes in firing rate and coefficient of variation. However, intrastriatal apomorphine did not always turn the activity of burst units into a more physiological pattern. STN lesions reduced the percentage of units responding to intrastriatal apomorphine in normal rats. In 60HDA-lesioned rats, STN lesions reduced the number of responsive units, and their change in mean firing rate and coefficient of variation. Our results show that the STN participates in the genesis of the bursting pattern of activity of SNpr units in 60HDA-lesioned rats, and that STN lesions can partially revert the abnormal spontaneous and apomorphine-induced responses of SNpr units in these animals.

Spontaneous and evoked activity of the caudate neurons to central and peripheral stimuli after brain lesions

The involvement of the cerebral cortex, commissural fibers and thalamus on caudate-caudate relations was studied in locally anesthetized, paralysed and artificially ventilated cats. This type of experimental preparation was necessary since a complete suppression of spontaneous and evoked activity is produced by subanesthetic doses of general anesthesia. Two types of caudate action potentials were encountered on the basis of their waveform characteristics: biphasic and triphasic spikes, the former being the largest population (80%). These waveforms were independent of the microelectrode resistance and the distance to recorded neurons. However, their responses were very similar to both central and peripheral stimuli. Caudate stimulation depressed the spontaneous discharges of the majority of the responsive units recorded within the opposite nucleus, while striatal neurons were activated by stimulation of the contralateral cortex. Decortication, thalamic lesion (motor nuclei and massa intermedia) and section of the corpus callosum decrease the firing rates of caudate neurons with biphasic spikes, while the discharges of the neurons with triphasic action potentials remained unchanged. Bilateral ablation of the cerebral cortex decreased the responsiveness of striatal neurons to contralateral nucleus and sciatic nerve and reduced the number of spontaneously active cells per recording tract. Section of the commissural fibers also depressed the caudate responses to the contralateral nucleus, and to the opposite precruciate cortex, although thalamic lesion did not affect the responsiveness of caudate cells to both central and peripheral stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of central and peripheral inputs on single pineal cell activity in the rat

The influences exerted by central and peripheral afferents to the pineal gland have been studied in rats anesthetized with urethane (1.2 g/kg, i.p.). Spontaneous action potentials arising from the pinealocytes were recorded by means of glass micropipettes filled with 3 M NaCl containing a dye. The electrical stimulation of suprachiasmatic nucleus, superior cervical ganglia, sciatic nerve and retina evoked discharge changes in a significant number of pineal cells. However, a relatively higher proportion of pinealocytes failed to respond to these afferents. Three types of responses could be observed. Inhibitions were the predominant response patterns to suprachiasmatic nucleus, superior cervical ganglia and sciatic nerve, while excitations were mainly elicited following photic stimulation, whereas the remaining evoked activity was biphasic responses, which were observed in a small number of cells after stimulation of suprachiasmatic nucleus, superior cervical ganglia and retina. These data confirm some previous neural inputs to the pineal and demonstrate the existence of a modulatory effect of the suprachiasmatic nucleus on pinealocyte discharges as well as somatosensory afferents to the gland by way of the sciatic nerve.