Acute white noise exposure affects the concentration of benzodiazepine receptors in the brain of the rat

Rats were acutely (45 min) exposed to 100-dB white noise, and benzodiazepine receptors in the cerebral cortex, hippocampus, and cerebellum were studied immediately after exposure by the receptor-binding assay using 3H-flunitrazepam as the ligand. An increase in the concentration of receptors was observed in the cerebral cortex, whereas no significant change in receptor concentration was seen in the hippocampus and cerebellum. No significant effect of noise on receptor binding affinity was detected in the three brain regions studied. Experimental handling also did not significantly affect the benzodiazepine receptor properties. These data confirm previous reports that acute exposure to stressor can cause rapid changes in benzodiazepine receptors in the brain.

Cyclosporine augments hepatic regenerative response in rats

A number of mechanisms participate in the hepatic injury that occurs during and following liver transplantation. A normal allograft regenerative response is probably essential for a successful transplant outcome. In this study, the effect of cyclosporine, a potent immunosuppressant used routinely after liver transplantation, on the regenerative response of the liver after partial hepatectomy was investigated. Male Wistar rats were pretreated for one week with either cyclosporine or the olive oil vehicle and were subjected to either a two-thirds partial hepatectomy or a sham operation. Animals were sacrificed at various times postoperatively and the remnant livers were weighed to determine the liver weight to body weight ratio, two biochemical measures of a regenerative response (cytosolic ornithine decarboxylase activity and thymidine kinase activity), and the hepatic content of estrogen and androgen receptors, as the content of these receptors has been shown to modulate, at least in part, the subsequent hepatic regenerative response. The preoperative hepatic cytosol content of ornithine decarboxylase, thymidine kinase, and estrogen receptor was significantly greater (P less than 0.05) in rats pretreated with cyclosporine than in those treated with the vehicle alone. A significant increase in ornithine decarboxylase and thymidine kinase activities occurred after partial hepatectomy in both the cyclosporine-pretreated and vehicle-pretreated animals. The absolute levels for each parameter were also greater in the cyclosporine-treated animals than in the vehicle-treated controls at 24 hr after partial hepatectomy (P less than 0.05). The pattern of change in the hepatic cytosolic content of estrogen and androgen receptors in both groups of animals was comparable with those described previously for regenerating liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cyclosporine on hepatic cytosolic estrogen and androgen receptor levels before and after partial hepatectomy

Estrogen and androgen receptors within the liver have been reported to modulate the hepatic regenerative response to partial hepatectomy. Moreover, cyclosporine has several untoward effects that might occur as a consequence of alterations in sex hormone activity. To evaluate these questions the following experiments were performed. Estrogen and androgen receptors in cytosol were quantitated in livers of rats treated with cyclosporine or olive oil vehicle before and after partial hepatectomy or a sham operation. Ornithine decarboxylase activity and thymidine kinase activity were assessed as indices of hepatic regeneration. Preoperative levels of estrogen receptor activity in the hepatic cytosol were significantly greater in rats treated with cyclosporine as compared to vehicle treated controls (P less than 0.01). In contrast, preoperative levels of androgen receptor activity in the cyclosporine-treated and vehicle-treated animals were similar. Following partial hepatectomy, a reduction in the activity of both sex hormone receptors in the hepatic cytosol was observed and was compatible with results described previously in normal animals. Unexpectedly the preoperative levels of ornithine decarboxylase (P less than 0.01) and thymidine kinase activity (P less than 0.01) were significantly greater in the rats treated with cyclosporine as compared to the vehicle treated controls. As expected, ornithine decarboxylase activity (at 6 hr) and thymidine kinase activity (at 24 hr) rose and peaked in response to a partial hepatectomy but were significantly greater (P less than 0.05) in the rats treated with cyclosporine as compared to the vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)

Repeated noise exposure affects muscarinic cholinergic receptors in the rat brain

We examined the effect of repeated exposure to 100-dB white noise (10 daily 45-min sessions) on muscarinic cholinergic receptors in different regions of the rat brain. Twenty-four hours after the last exposure session, increase in concentration (Bmax) of [3H]quinuclidinyl benzilate ([3H]-QNB) binding sites was observed in the hippocampus, but no significant change was seen in the striatum, frontal cortex, and hypothalamus. No significant effect of noise on receptor binding affinity (Kd) was found. Pretreating the rats with naltrexone (1 mg/kg, IP) before exposure blocked the noise-induced increase in cholinergic receptors in the hippocampus.

Low-level microwave irradiation and central cholinergic systems

Our previous research showed that 45 min of exposure to low-level, pulsed microwaves (2450-MHz, 2-microseconds pulses, 500 pps, whole-body average specific absorption rate 0.6 W/kg) decreased sodium-dependent high-affinity choline uptake in the frontal cortex and hippocampus of the rat. The effects of microwaves on central cholinergic systems were further investigated in this study. Increases in choline uptake activity in the frontal cortex, hippocampus, and hypothalamus were observed after 20 min of acute microwave exposure, and tolerance to the effect of microwaves developed in the hypothalamus, but not in the frontal cortex and hippocampus, of rats subjected to ten daily 20-min exposure sessions. Furthermore, the effects of acute microwave irradiation on central choline uptake could be blocked by pretreating the animals before exposure with the narcotic antagonist naltrexone. In another series of experiments, rats were exposed to microwaves in ten daily sessions of either 20 or 45 min, and muscarinic cholinergic receptors in different regions of the brain were studied by 3H-QNB binding assay. Decreases in concentration of receptors occurred in the frontal cortex and hippocampus of rats subjected to ten 20-min microwave exposure sessions, whereas increase in receptor concentration occurred in the hippocampus of animals exposed to ten 45-min sessions. This study also investigated the effects of microwave exposure on learning in the radial-arm maze. Rats were trained in the maze to obtain food reinforcements immediately after 20 or 45 min of microwave exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Mode of alloantibody-mediated blockade of allo-sensitization for tumor allograft rejection

The mode of alloantibody-mediated inhibition of allo-sensitization for tumor allograft rejection was studied. Relatively small amounts of anti-H-2d alloantiserum administered shortly before or after injection of allogeneic spleen cells blocked the allo-sensitization for second-set tumor allograft rejection. In contrast, the alloantiserum injected shortly before inoculation of tumor barely enhanced the tumor growth. The passively administered alloantiserum inhibited the sensitization for allospecific cytotoxic T lymphocyte responses in vitro. Further study revealed that the allo-sensitization could be blocked with antiserum specific against only one of the expressed H-2 antigens on stimulator cells. Correspondingly, H-2Dd-monospecific monoclonal antibody (IgG2a) was effective in inhibiting the sensitization with cells expressing multiple H-2 alloantigens. These results suggest that antibody-mediated inactivation of stimulator cells as a whole is an important mechanism of the allograft enhancement.

The effect of different types of hepatic injury on the estrogen and androgen receptor activity of liver

Mammalian liver contains receptors for both estrogens and androgens. Hepatic regeneration after partial hepatectomy in male rats is associated with a loss of certain male-specific hepatic characteristics. In this study we investigated the effects of lesser forms of hepatic injury on the levels of estrogen and androgen receptor activity in the liver. Adult male rats were subjected to portacaval shunt, partial portal vein ligation, hepatic artery ligation, or two-thirds partial hepatectomy. Another group of animals was treated with cyclosporine. At the time of sacrifice the livers were removed and used to determine the estrogen and androgen receptor activity in the hepatic cytosol. A significant reduction (p less than 0.05) in the hepatic cytosolic androgen receptor activity and a slight increase in the estrogen receptor activity occurred following total portosystemic shunting. Partial ligation of the portal vein, which produces a lesser degree of portosystemic shunting, had no effect on the levels of the estrogen and androgen receptor activity present within hepatic cytosol. Cyclosporine-treated animals had significantly greater (p less than 0.01) levels of estrogen receptor activity in the hepatic cytosol compared to vehicle-treated control animals. Levels of estrogen and androgen receptor activity within the hepatic cytosol remained unchanged after ligation of the hepatic artery. The reduction in the cytosolic estrogen and androgen receptor activity in the liver after partial hepatectomy was confirmed. In summary, certain types of hepatic injury are associated with profound changes in the estrogen and androgen receptor content within the liver.

Low-level microwave irradiation and central cholinergic activity: a dose-response study

Rats were irradiated with circularly polarized, 2,450-MHz pulsed microwaves (2-microseconds pulses, 500 pulses per second [pps]) for 45 min in the cylindrical waveguide system of Guy et al:(Radio Sci 14:63-74, 1979). Immediately after exposure, sodium-dependent high-affinity choline uptake, an indicator of cholinergic activity in neural tissue, was measured in the striatum, frontal cortex, hippocampus, and hypothalamus. The power density was set to give average whole-body specific absorption rates (SAR) of 0.3, 0.45, 0.6, 0.75, 0.9, or 1.2 W/kg to study the dose-response relationship between the rate of microwave energy absorption and cholinergic activity in the different areas of the brain. Decrease in choline uptake was observed in the striatum at a SAR of 0.75 W/kg and above, whereas for the frontal cortex and hippocampus, decreases in choline uptake were observed at a SAR of 0.45 W/kg and above. No significant effect was observed in the hypothalamus at the irradiation power densities studied. The probit analysis was used to determine the SAR50 in each brain area, i.e., the SAR at which 50% of maximum response was elicited. SAR50 values for the striatum, frontal cortex, and hippocampus were 0.65, 0.38, and 0.44 W/kg, respectively.

TRH analog MK-771 reverses neurochemical and learning deficits in medial septal-lesioned rats

Microinjection of ibotenic acid into medial septum of rats decreased choline acetyltransferase (CAT) and high-affinity choline uptake (HACU) activities in hippocampus and retarded the learning of a spatial memory task in the radial-arm maze. Administration of MK-771, a stable TRH analog, to such animals restored HACU activity in hippocampus to normal levels. Daily treatment of rats with MK-771 prior to maze running also restored the animals' learning ability. MK-771 did not enhance hippocampal HACU activity or maze performance in sham-lesioned rats. These results suggest that MK-771 reversed the ibotenic acid-induced memory deficit by restoring septohippocampal cholinergic function. MK-771 and other TRH analogs may represent novel agents for improving memory deficits produced by cholinergic insufficiency in Alzheimer's disease.

Effects of repeated exposure to white noise on central cholinergic activity in the rat

Acute (45 min) exposure to noise has been shown to decrease sodium-dependent high-affinity choline uptake activity in the frontal cortex and hippocampus of the rat. In the present experiment, the effects of repeated noise exposure on choline uptake in these two brain regions were studied. Rats were exposed to 100-dB white noise in ten 45-min sessions. Tolerance developed to the effects of noise on choline uptake. In addition, the effects were found to be classically conditionable to cues in the exposure environment. These data may have important implications in understanding the health hazard of noise exposure in both the public and occupational environments.

Acute low-level microwave exposure and central cholinergic activity: studies on irradiation parameters

Sodium-dependent high-affinity choline uptake was measured in the striatum, frontal cortex, hippocampus, and hypothalamus of rats after acute exposure (45 min) to pulsed (2 microseconds, 500 pps) or continuous-wave 2,450-MHz microwaves in cylindrical waveguides (Guy et al.: Radio Science 14:63-74, 1979) or miniature anechoic chambers (Guy: Journal of Microwave Power 14:327-338, 1979). In all exposure conditions, the average whole-body specific absorption rate was at 0.6 W/kg. Decrease in choline uptake was observed in the frontal cortex after microwave exposure in all of the above irradiation conditions. Regardless of the exposure system used, hippocampal choline uptake was decreased after exposure to pulsed but not continuous-wave microwaves. Striatal choline uptake was decreased after exposure to either pulsed or continuous-wave microwaves in the miniature anechoic chamber. No significant change in hypothalamic choline uptake was observed under any of the exposure conditions studied. We conclude that depending on the parameters of the radiation, microwaves can elicit specific and generalized biological effects.

Effects of intraseptal drug administration on pentobarbital-induced narcosis and hippocampal choline uptake

Effects of injection of drugs into the septum on pentobarbital anesthesia were investigated in the rat. Intraseptal microinjection of bicuculline (5 micrograms), arecoline (2 micrograms), and phenylephrine (5 micrograms) shortened, MK-212 (5 micrograms) prolonged, and atropine (2 micrograms) had no significant effect on the duration of pentobarbital-induced loss of righting reflex. Bicuculline and arecoline increased and MK-212 reduced hippocampal cholinergic activity as measured by change in hippocampal sodium-dependent high-affinity choline uptake after intraseptal drug injection. It is concluded that activation of the septal-hippocampal cholinergic pathway might be an important neuromechanism for recovery from pentobarbital-narcosis.

Neural mechanisms mediating the hyperthermia elicited by prostaglandin E2 injected into the preoptic-anterior hypothalamus

The neuromechanism mediating the hyperthermia induced by injection of PGE2 into the preoptic/anterior hypothalamus (PO/AH) was investigated in the rat. Pretreatment of rats with intraperitoneal injection of atropine sulfate blocked, whereas pretreatment with atropine methyl bromide had no significant effect on the hyperthermia. In a second series of experiments, atropine sulfate was microinjected into different regions of the hypothalamus and the thalamus in an attempt to locate the central cholinergic synapses involved in the PGE2-induced hyperthermia. The hyperthermia was blocked by atropine injection into the dorsal/dorsomedial hypothalamic area (DH), but was not significantly affected by injection into the PO/AH, ventromedial hypothalamus, or the thalamic area above the DH. Moreover, microinjection of the cholinergic agonist carbachol (0.5 microgram) into the DH could also elicit hyperthermia. Thus, our data suggest that the hyperthermia induced by PGE2 administration into the PO/AH is mediated by a cholinergic mechanism in the DH.

Acute exposure to noise affects sodium-dependent high-affinity choline uptake in the central nervous system of the rat

Rats were acutely (45 min) exposed to white noise at intensity of either 70 or 100 dB. Sodium-dependent high-affinity choline uptake was determined in the striatum, frontal cortex, hypothalamus, and hippocampus immediately after exposure. The effects of noise on choline uptake varied according to the intensity of the noise and the brain area studied. Exposure to noise of 70 dB significantly increased the choline uptake in the frontal cortex, hypothalamus, and hippocampus as compared to the uptake of sham-exposed rats, whereas decreased choline uptake in the frontal cortex and hippocampus was observed acute exposure to noise of 100 dB. No significant effect on choline uptake in the striatum was seen after exposure to noise of either intensity. In addition, pretreatment of the rats with the narcotic antagonist naltrexone (1 mg/kg, IP) before noise exposure blocked the effects of noise on choline uptake in the central nervous system. Changes in cholinergic activity in the central nervous system could be a response to the stress effect of noise and may be mediated by endogenous opioids.

Effects of low-level microwave irradiation on hippocampal and frontal cortical choline uptake are classically conditionable

In previous research, we found that sodium-dependent high-affinity choline uptake in the hippocampus and frontal cortex of the rat was lowered after acute (45 min) exposure to low-level 2450-MHz pulsed microwaves (power density 1 mW/cm2; average whole body specific absorption rate, 0.6 W/kg; 2 mu sec pulses, 500 pps). In the present experiment, we investigated developments of tolerance and classical conditioning to these effects of microwaves. Rats were exposed to microwaves in cylindrical waveguides in 10 daily sessions (45 min per session). In an 11th session, we subjected the rats to either microwave (study of tolerance) or sham exposure (study of conditioned effect) for 45 min, and immediately measured choline uptake in the hippocampus and frontal cortex. We found that tolerance, a decrease in response to microwaves, developed to the effect of microwaves on choline uptake in the hippocampus, but not in the frontal cortex. Conditioned effects were also observed: an increase in choline uptake in the hippocampus and a decrease in uptake in the frontal cortex. These data suggest that the effects of microwaves on choline uptake in the hippocampus and frontal cortex are classically conditionable, probably to cues in the exposure environment.

Low-level microwave irradiations affect central cholinergic activity in the rat

Sodium-dependent high-affinity choline uptake was measured in various regions of the brains of rats irradiated for 45 min with either pulsed or continuous-wave low-level microwaves (2,450 MHz; power density, 1 mW/cm2; average whole-body specific absorption rate, 0.6 W/kg). Pulsed microwave irradiation (2-microseconds pulses, 500 pulses/s) decreased choline uptake in the hippocampus and frontal cortex but had no significant effect on the hypothalamus, striatum, and inferior colliculus. Pretreatment with a narcotic antagonist (naloxone or naltrexone; 1 mg/kg i.p.) blocked the effect of pulsed microwaves on hippocampal choline uptake but did not significantly alter the effect on the frontal cortex. Irradiation with continuous-wave microwaves did not significantly affect choline uptake in the hippocampus, striatum, and hypothalamus but decreased the uptake in the frontal cortex. The effect on the frontal cortex was not altered by pretreatment with narcotic antagonist. These data suggest that exposure to low-level pulsed or continuous-wave microwaves leads to changes in cholinergic functions in the brain.

Age-related decreases in dopamine receptors in the caudate nucleus and putamen of the rhesus monkey (Macaca mulatta)

Specific binding of the dopamine receptor ligand 3H-spiroperidol to cell membranes prepared from the caudate nuclei and putamens of 29 rhesus monkeys (M. mulatta), ranging in age from 2 to 22 years, was investigated. Receptor concentration (Bmax) decreased in the caudate nucleus and putamen with age at mean rates of 2.1 and 1.7% per year, respectively, whereas binding affinity (Kd) did not change significantly with age. The rate of decline in Bmax appeared to be more rapid before adulthood and in old age than during young adulthood and middle age. These data are compared with the results from similar studies of other animal species including human, rabbit, rat, and mouse. The rate of decline in striatal dopamine receptors is closely related to the rate of aging and maximal life span of the species. It may reflect both maturational and senescent processes modifying the behavior of animals as they age.

The effect of different treatment modalities on connective tissue attachment

This study compared the effect of four treatment modalities on connective tissue attachment. Ligature-induced periodontitis was established around the mandibular premolars of five young beagle dogs over 8 weeks. Following a 2-week period without ligatures, a reference dog was sacrificed to estimate the extent and nature of the disease. Three dogs received flap procedures in one mandibular posterior segment, and the six experimental roots were treated with citric acid (pH 1) for 3 minutes; the contralateral mandibular segments received flap procedures and the roots were treated with 4% chlorhexidine gluconate in the Hibiclens preparation for 3 minutes. One segment of the control dog received flap procedures, and the roots were treated with sterile normal saline; the contralateral segment received closed root planning. The experimental dogs were sacrificed 1, 2 and 3 months after treatment. The control dog was sacrificed 3 months postoperatively. One week before sacrifice each dog received a Procion dye injection. At sacrifice the study segments of all four treated dogs were clinically healthy, with no observable differences between the different treatment modalities. Histologically, the 1, and 3-month chlorhexidine, the 3-month saline and 3-month root planed specimens had long junctional epithelial adhesions with little connective tissue attachment. The 2-month chlorhexidine and all citric acid-treated sections showed appreciable amounts of new connective tissue attachment. Some 2-month and 3-month citric acid and 2-month chlorhexidine sections showed cementum over the apical portion of the long junctional epithelium. The frequency of occurrence and the length of cementum overlapping epithelium increased appreciably over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-dependent, high-affinity choline uptake in hippocampus and frontal cortex of the rat affected by acute restraint stress

Acute (45-min) restraint stress decreased sodium-dependent, high-affinity choline uptake in the hippocampus and frontal cortex of rats. The effect of restraint on the hippocampus was blocked, whereas that on the frontal cortex was not significantly affected, by pretreatment of the rats with the narcotic antagonist naltrexone (1 mg/kg, i.p.) immediately prior to restraint.

Decreased muscarinic acetylcholine receptor number in the central nervous system of the tottering (tg/tg) mouse

The tottering mouse (tg/tg) is a single-locus mutant, phenotypically characterized by the development of epilepsy associated with distinct electroencephalographic abnormalities. Because of reported alterations in muscarinic receptor (mAChR) number in various seizure states, mAChR density was examined in discrete brain regions of tottering (tg/tg) and coisogenic wild-type (+/+) mice. Saturation binding experiments revealed a widespread decrease in membrane mAChR density in the CNS of adult tottering (tg/tg) mice as compared with age-matched control wild-type (+/+) mice. The decrease was most pronounced in the hippocampus, where tg/tg mice exhibited a 40-60% reduction in mAChR density with no change in the affinity of the receptor for antagonists or agonists. At postnatal day 10, before the reported onset of electroencephalographic abnormalities, 114 and 65% increases in mAChR density were observed in the tg/tg hippocampus and cortex, respectively. Following the development of seizure activity at postnatal day 22, mAChR density in the tg/tg hippocampus was reduced by 29%. No change in brain mAChR density was seen in adult heterozygotes (+/tg), which do not develop electroencephalographic or seizure abnormalities. These results indicate that the development of reduced mAChR number in the CNS of the tg/tg mouse is secondary to abnormal neuronal activity, providing further support for the hypothesis that membrane depolarization can cause a decrease in neuronal mAChR density.

Low-level microwave irradiation attenuates naloxone-induced withdrawal syndrome in morphine-dependent rats

The effect of microwave irradiation on naloxone-induced withdrawal syndrome was studied in rats made morphine dependent by subcutaneous implantation of morphine pellets. Morphine-dependent rats were either exposed to pulsed low-level microwaves (2450 MHz, 1 mW/cm2, 500 pps, 2 musec pulses) or sham-irradiated for 45 min before the naloxone injection. We found that microwave-exposed rats showed significantly less weg-dog-shakes and had higher body temperature than the sham-exposed animals during withdrawal. There was no significant difference in the incident of diarrhea between the two groups of animals. These data further support the results of our previous research suggesting that pulsed low-level microwave irradiation activates endogenous opioids in the rat.

Effects of low-level microwave irradiation on amphetamine hyperthermia are blockable by naloxone and classically conditionable

In a series of experiments, we investigated the effects of pulsed low-level microwave irradiation on amphetamine-induced hyperthermia in the rat. Rats were irradiated in a 2,450-MHz cylindrical waveguide exposure system at 1 mW/cm2, 2 mus pulses, 500 pps, average SAR of 0.6 W/kg. Acute (45 min) exposure to microwaves attenuated amphetamine-induced hyperthermia. This effect was blocked by pretreatment of the animals with the narcotic antagonist naloxone. In another experiment, rats were subjected to ten daily sessions of microwave exposure (45 min/session). On day 11, amphetamine-induced hyperthermia was studied in the animals immediately after a session of either microwave or sham exposure. Similar to the acute effect, amphetamine-induced hyperthermia was attenuated in rats irradiated with microwaves (unconditioned effect). In the sham-irradiated animals we observed a potentiation of the amphetamine-induced hyperthermia, which was a conditioned effect of microwaves. Thus, the conditioned effect (potentiation) was opposite in direction to the unconditioned effect (attenuation). No tolerance developed to the unconditioned effect after subchronic exposure. Furthermore, both conditioned and unconditioned effects of microwaves on amphetamine-induced hyperthermia could be blocked by treatment with naloxone. These data suggest that microwave irradiation may activate endogenous opioids, which in turn alter the actions of psychoactive drugs, and the effect of microwaves on drug action can be classically conditioned.

Intraseptal microinjections of substance P and analogs potentiate pentobarbital-induced narcosis and depression of hippocampal cholinergic activity

Intraseptal microinjection of Substance P (SP) has been shown to depress activity in the septal-hippocampal cholinergic pathway in the rat. Pentobarbital also depresses septal-hippocampal cholinergic activity, and a relationship between this depressed activity and pentobarbital-induced narcosis is suggested by a variety of studies. To examine this relationship further, we microinjected SP and its analogs, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP and [D-Pro2, D-Trp7,9]-SP, intraseptally in rats pretreated with pentobarbital, and measured the duration of loss of righting reflex and change in choline uptake in hippocampal synaptosomes. The duration of pentobarbital-induced loss of righting reflex was prolonged and the pentobarbital-induced reduction of hippocampal choline uptake was enhanced by all three drugs. A negative correlation (r = -0.96, P less than .02) was seen between duration of loss of righting reflex and synaptosomal choline uptake. Thus, the two analogs of SP appear to act as SP agonists at the septum, judged by their abilities to potentiate pentobarbital narcosis and reduce septal-hippocampal cholinergic activity. This is in contrast to reported actions of these two analogs as SP antagonists in various peripheral tissues.