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Biomedical subjects

J M Lipton

Publications and source records attributed to J M Lipton.

At least 199 records · Page 11Linked to original sources
PubMed1973

Central and peripheral temperatures and EEG changes during behavioural thermoregulation in pigs.

Pigs aged about 8 weeks will learn to operate infra-red heaters at ambient temperatures of 20 degree Celsius but not at 25 degree Celsius. Hypothalamic temperature, cortical EEG and skin temperatures have been recorded in pigs exposed to ambient temperatures of 0, +10 or +20 degree Celsius in both heat reinforcement and heat escape situations. The amount of heating received decreased with increasing ambient temperature but at any given ambient temperature there was no significant difference between the duration of heating obtained in the heat reinforcement or heat escape situations. At O degree Celsius, in both situations, the pigs tended to maintain the temperature of their skin which was nearest the heaters at higher levels than they did at +10 degree Celsius. Skin temperatures rarely exceeded 45 degree Celsius. The temperature of the preoptic region was variable but did not change systematically with respect to the behaviour. Observation of the pigs and cortical EEG revealed that during periods of infra-red heating the pigs often became drowsy, but "post reinforcement synchrony" was not seen in the EEG. Cooling the preoptic region by means of an implanted thermode increased the duration of heating in a heat reinforcement situation at 0 degree Celsius and resulted in skin temperatures reaching levels of 45-47 degree Celsius.

Animals↗
PubMedDate not supplied

Effects of sodium salicylate, aminopyrine and chlorpromazine on behavioral temperature regulation.

To characterize drug actions on thermoregulatory processes it is necessary to know whether compounds which alter body temperature also cause changes in thermoregulatory motivation. In the present experiments the effects of sodium salicylate, aminopyrine and chlorpromazine (CPZ) on rectal temperature (Tre) and behavior were measured in rats trained to escape heat and obtain cooling. All three drugs produced hypothermia in a 23 degree C environment but the effects upon behavior suggest that the compounds have different actions. Sodium salicylate (60-300 mg/kg) increased the amount of time spent responding to escape heat and obtain cooling so that Tre was held below control levels. Aminopyrine (12.5-75 mg/kg) did not alter thermoregulatory motivation even though it caused marked hypothemia. The time spent responding decreased after CPZ (2 and 3 mg/kg) so that drug-induced hypothermias were compensated. The results suggest that sodium salicylate influences the central mechanisms of physiological and behavioral temperature control whereas CPZ affects either peripheral thermoeffectors or central effector pathways without disrupting thermoregulatory motivation. Aminopyrine is presumed to act on central temperature controls to lower body temperature and, at the same time, to reduce the significance of the low body temperature to behavior.

Aminopyrine↗
PubMedDate not supplied

Peripheral administration of alpha-MSH reduces fever in older and younger rabbits.

In these experiments IV, ICV and intra-gastric administration of alpha-MSH reduced fever caused by injections of leukocytic pyrogen (LP). 2.5 micrograms alpha-MSH injected IV reduced fever caused by IV LP, more so in rabbits over 3 yrs old than in those under 2 yrs of age; 5 mg of acetaminophen given IV had no antipyretic effect in either age group. ICV administration of 25 ng alpha-MSH reduced fever caused by IV LP injection in the older but not in the younger rabbits, alpha-MSH given IV (2.5 micrograms) also lowered fever induced by ICV injection of LP in older but not in younger animals. Both older and younger rabbits showed reductions in fever evoked by IV LP after 2.5 mg alpha-MSH was given by gastric tube. The results indicate that this peptide which occurs naturally within the brain has potent antipyretic properties when given systemically, presumably as a result of a central antipyretic action. Greater sensitivity to central alpha-MSH in the older rabbits may account for the reduced febrile response seen in the aged. The findings support previous data which suggest that central alpha-MSH has a physiological role in the limitation of fever.

Acetaminophen↗
PubMedDate not supplied

Intracerebroventricular and septal injections of arginine vasopressin are not antipyretic in the rabbit.

Arginine vasopressin (AVP) has been reported to have an antipyretic effect in the ewe and guinea pig near term. Perfusions with AVP of sites in the septal region also reduced fever in non-pregnant sheep. In the present experiments adult rabbits with third cerebral ventricular or septal cannulas were restrained in a 23 degree C environment, and rectal temperature was recorded every 10 min. Fever induced by IV administration of leukocytic pyrogen was not reduced by AVP (25-100 ng) given intraventricularly 20 min later. Doses of 1-5 micrograms AVP injected into the septum likewise were not antipyretic but actually caused an increase in fever. This augmentation of the febrile response is consistent with results of previous studies in this laboratory in which AVP increased hyperthermia in a hot environment and enhanced hyperthermic responses to PGE2. The data from these experiments provide no evidence that central AVP is an endogenous antipyretic in rabbits; rather, it may be that central AVP augments fever in this species.

Animals↗