Biomedical subjects

N R Marshall

Publications and source records attributed to N R Marshall.

14 recordsLinked to original sources

PubMed1990

Behavioural thermoregulation in mice: effects of low doses of general anaesthetics of different potency.

Chloroform, monochlorodifluoromethane and nitrous oxide produced dose-related decreases in the rectal temperatures of mice allowed to choose between a warm and a cool environment. The doses used were subanaesthetic, respectively 0.0013-0.004, 0.028-0.085 and 0.25-0.5 atm. The hypothermia (up to 3.6 degrees C) was usually associated with significant reductions in time spent in the warm. The log dose-hypothermic response plots were approximately parallel and there was a marked correlation between anaesthetic potency, as measured by the abolition of the righting response, and hypothermic potency.

Anesthetics↗

PubMed1989

Behavioral thermoregulation in mice subjected to high pressure.

Mice exposed to normoxic He and Ne at increased pressure and allowed to choose between a neutral and a cool environment showed a preference for the cooler environment. This behavior was apparent at 5.7 but not at 2.5 atm He. At 11.3 atm He and Ne, the behavior was associated with a similar reduction in the deep body temperature to a new steady level. The reduction in body temperature increased with pressure, up to 35 atm He, the maximum studied. Since the heat transfer of the He and Ne gas mixtures is different and both gases exert negligible anesthetic effects, the hydrostatic pressure most likely affects behavioral thermoregulation by affecting neuronal function.

Animals↗

PubMed1986

Effects of subanesthetic doses of inert gases on behavioral thermoregulation in mice.

Mice exposed to subanesthetic partial pressures of N2O (0.25 to 0.75 atm) or N2 (5.7 or 11.33 atm) and allowed to choose between a warm and a cool environment showed a marked preference for the cooler environment. This behavior was associated with the onset of hypothermia, with deep body temperature falling by up to about 3 degrees C, usually to a new, steady level. Both the length of time spent in the cooler environment and the degree of the hypothermia produced increased with the partial pressure of N2O or N2 used. The effects of N2O on behavioral thermoregulation and body temperature were reversible. There was a correlation between anesthetic potency and the ability of both gases to alter thermoregulation, suggesting that the effect of these agents on thermoregulation was caused by the same molecular interactions as those which underlie anesthesia. Since both gases elicited changes in behavioral thermoregulation promoting rather than opposing the onset of hypothermia, it is concluded that they may have acted to lower the level at which deep body temperature was being regulated.

Anesthetics↗

PubMed1984

Forskolin and the release of noradrenaline in cerebrocortical slices.

The role of adenosine 3',5'-cyclic monophosphate (cAMP) in the release of noradrenaline from central neurones has been investigated by examining the effects of forskolin, 3-isobutyl-l-methylxanthine (IBMX), cis-6-(p-acetamidophenyl)-1,2,3,4,4a, 10b-hexahydro-8,9-dimethoxy-2-methyl-benzo[c] [1,6]-naphthyridine bis (+ +hydrogenmaleinate) (AH21-132; a new phosphodiesterase inhibitor) and N6,O2'-dibutyryl-adenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP) on the outflow of tritiated compounds from rat and rabbit cerebral cortex slices preincubated with [3H]-noradrenaline. Forskolin, IBMX, AH21-132 and dibutyryl-cAMP produced a concentration-dependent increase in both basal and electrically-evoked efflux of tritium from rat and rabbit cortex slices. The increase in basal tritium efflux from rabbit cortex slices elicited by forskolin and IBMX could be attributed mainly to an increase in [3H]-DOPEG although a small increase in [3H]-noradrenaline was also observed. Forskolin and (when combined with noradrenaline) IBMX and AH21-132 increased the cAMP content of rat cortex slices at similar or somewhat higher concentrations that they increased tritium efflux. Neither forskolin nor IBMX or AH21-132 had any effect on the cocaine-sensitive uptake of [3H]-noradrenaline into synaptosomes prepared from rat or rabbit cortex. The effects of forskolin, IBMX and dibutyryl-cAMP on electrically-evoked overflow of tritium from rat and rabbit cortex slices were reduced when cocaine (10 microM) was present in the superfusion medium, although forskolin produced a similar increase in cAMP in the absence or presence of cocaine. It is suggested that cAMP may facilitate the normal process of noradrenaline release by nerve stimulation.

1-Methyl-3-isobutylxanthine↗

PubMed1973