Hypothermia produced by chloralose acting on the hypothalamus

Stability of the acetic acid-induced bladder irritation model in alpha chloralose-anesthetized female cats

Time- and vehicle-related variability of bladder and urethral rhabdosphincter (URS) activity as well as cardiorespiratory and blood chemistry values were examined in the acetic acid-induced bladder irritation model in α-chloralose-anesthetized female cats. Additionally, bladder and urethra were evaluated histologically using Mason trichrome and toluidine blue staining. Urodynamic, cardiovascular and respiratory parameters were collected during intravesical saline infusion followed by acetic acid (0.5%) to irritate the bladder. One hour after starting acetic acid infusion, a protocol consisting of a cystometrogram, continuous infusion-induced rhythmic voiding contractions, and a 5 min "quiet period" (bladder emptied without infusion) was precisely repeated every 30 minutes. Administration of vehicle (saline i.v.) occurred 15 minutes after starting each of the first 7 cystometrograms and duloxetine (1mg/kg i.v.) after the 8(th). Acetic acid infusion into the bladder increased URS-EMG activity, bladder contraction frequency, and decreased contraction amplitude and capacity, compared to saline. Bladder activity and URS activity stabilized within 1 and 2 hours, respectively. Duloxetine administration significantly decreased bladder contraction frequency and increased URS-EMG activity to levels similar to previous reports. Cardiorespiratory parameters and blood gas levels remained consistent throughout the experiment. The epithelium of the bladder and urethra were greatly damaged and edema and infiltration of neutrophils in the lamina propria of urethra were observed. These data provide an ample evaluation of the health of the animals, stability of voiding function and appropriateness of the model for testing drugs designed to evaluate lower urinary tract as well as cardiovascular and respiratory systems function.

Thermal stimulation of hypothalamic neurones in unanaesthetized rabbits

1. A technique has been devised for recording unit activity in the anterior hypothalamus of conscious rabbits during the controlled displacement of local temperature by 1-2 degrees C. The region at 1 and 2 mm from the mid line was explored.2. All the units studied showed spontaneous activity before thermal stimulation with a mean rate of 9 impulses/sec (range 1/16 sec to 65/sec).3. Twenty-seven (10%) of the recorded neurones showed a change in firing rate which could be related to the temperature changes. Twenty-one of the cells were ;warm-sensitive' and were excited when temperature was raised or inhibited when it was lowered. The other six units were ;cold-sensitive' and showed the opposite type of response.4. Apart from this directional grouping, it was possible to classify the responses into four categories: A, five cells whose firing rate was always proportional to local temperature over a range from 2 degrees C below to 2 degrees C above body temperature; B, six cells whose average level of firing changed during the period of observation, but whose sensitivity to temperature was not affected; C, eight cells which showed a threshold and were only affected by temperature above or below a certain level; D, four cells whose changes in frequency either led or lagged behind the temperature changes.5. The positions of these sensitive units in the hypothalamus did not show any apparent pattern, except that 75% of them were found 1 mm lateral to the mid line; the remaining 25% were 2 mm lateral.