Decrease in core temperature as an indication of cholinergic overdrive during amitriptyline withdrawal

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26498/1/0000034.pd

Bright artificial light produces subsensitivity to clonidine

The authors used a thermoregulation paradigm to test the hypothesis that chronic treatment with bright artificial light produces subsensitivity to the hypothermic effects of clonidine, an [alpha]2-agonist. One week of treatment produced blunting of the hypothermic response to clonidine (p 2-receptor.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27582/1/0000626.pd

Effects of placebo (saline) injections on core temperature in the rat

1. Core temperature was telemetrically measured in 15 rats before (i.e., at baseline) and at 10-min intervals for 120 min following the injection of normal saline (1 ml/kg ip) or "no injection."2. The sample exhibited a mean temperature increase of 0.60 +/- 0.10[deg]C(mean +/- SEM) following injection.3. This differed significantly from the mean increase of 0.13 +/- 0.03[deg]C following "no injection" (p 4. The injection of saline (1 ml/kg) affected a mean rise in core temperature of 0.55 +/- 0.07[deg]C (p > 0.000001) in 46 animals in a second experiment.5. These data indicate that routine handling and a simple injection comprise significant and measurable stress which must be controlled in neuropharmacological studies employing a thermoregulation paradigm.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28880/1/0000716.pd

Bright artificial light produces subsensitivity to nicotine

Bright artificial light is a treatment for seasonal depression. Eleven (11) rats were exposed to bright artificial light (11,500 lux) for two consecutive weeks. The thermic response to nicotine was measured prior to light exposure and after one and two weeks of treatment. The thermic response to nicotine at baseline was -1.69 +/- 0.25[deg]C (mean +/- SEM). The thermic response to nicotine was -0.66 +/- 0.12[deg]C (p < 0.002) after one and +0.31 +/- 0.14[deg]C (p < 0.000025) after two weeks of light exposure. The change in temperature was different between weeks one and two (p < 0.000025). The exposure of animals to constant light at an intensity of 300 lux did not blunt the hypothermic response to nicotine. These findings suggest that bright artificial light, like other antidepressant treatments, produces subsensitivity of a nicotinic mechanism involved in the regulation of core temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27513/1/0000557.pd

Chronic treatment with ethanol produces supersensitivity to oxotremorine

1. The effect of chronic treatment with ethanol (14% v:v in drinking water) on the physiological endpoint core temperature which is partially regulated by a muscarinic mechanism was measured in adult male rats (n = 8).2. One and two weeks of treatment were associated with enhancement of the hypothermie response to oxotremorine, 0.25 mg/kg ip ((p = 0.0005 and p = 0.0001, respectively).3. The sample remained supersensitive to this muscarinic agonist 48 and 96 hours after the discontinuation of treatment (p = 0.0014 and p = 0.013 respectively).4. Repeated injections of oxotremorine, 0.25 mg/kg ip, every other day for 10 days did not produce carry-over effects in a control experiment.5. The results suggest that ethanol renders muscarinic mechanisms supersensitive during chronic treatment and that Supersensitivity remains up to 96 hours following withdrawal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28878/1/0000713.pd

The anorectic effects of CRH and restraint stress decrease with repeated exposures

Intracerebroventricular (icv) administration of corticotropin-releasing hormone (CRH) or exposure to a restraint stressor causes acute anorexia in rats. However, the effects on food intake of repeated injections of CRH or repeated exposures to restraint stress have not been previously reported. As the effects of these more chronic CRH and stress treatments may be of greater relevance to emerging hypotheses of the pathogenesis of human eating and affective disorders, we measured the changes in food intake and body weight of rats after repeated central injections of CRH. In two experiments using two different daily dosages of CRH and two different schedules of administration, we found that the anorectic effect of CRH decreased over repeated injections. Weight gain was slowed significantly only in the high-dose experiment. Rats may become tolerant to the anorectic effects of CRH delivered by repeated icv injections. These findings have important implications for hypothesized mechanisms of anorexia nervosa and/or depression.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28570/1/0000373.pd

Effects of preferential delta and kappa opioid receptor agonists on the intake of hypotonic saline

A previous study has implicated central mu opioid receptors in the preference for salt solutions. Because mu, kappa and delta receptors are all thought to play a role in food intake and/or the mediation of palatability, we performed a series of experiments to determine whether preferential agonists at kappa and delta receptors might also stimulate the intake of salt solutions. When injected centrally into nondeprived rats, two selective agonists at delta receptors caused increases in the intake of 0.6% saline; the intake of concurrently available water was either unchanged or slightly increased. The selective kappa agonist U-50, 488H had no effect on water or saline intake, whereas the preferential kappa agonist DAFPHEDYN caused a delayed increase in saline intake. These results indicate a role for central delta receptors in the preference for salt solutions, and are consistent with the suggestion that opioids play a role in the mediation of palatability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28718/1/0000539.pd

Mecamylamine pretreatment increases subsequent nicotine self-administration as indicated by changes in plasma nicotine level

Acute administration of mecamylamine, a centrally active nicotinic cholinergic agonist, has been shown to increase amount of smoking as indicated by smoking topography (e.g., puff rate, puff duration), expired carbon monoxide changes, and other inferential measures. In the present study, subjects showed significantly greater increases in plasma nicotine following smoking of two high-nicotine research cigarettes when pretreated with mecamylamine than when pretreated with placebo, even though no significant differences in puff volume or puff number were detected. Interestingly, none of our subjects reported nausea, although some achieved plasma nicotine levels at which nausea would typically be expected. We attribute the observed increases in nicotine intake to compensatory behavior designed to overcome mecamylamine's blocking effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46446/1/213_2004_Article_BF00518198.pd

Telemetric measurement of core temperature in pharmacological research: Validity and reliability

1. The authors present data establishing the reliability and validity of a method for telemetrically measuring core temperature.2. The method is designed to be of particular utility to psychobiological researchers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28902/1/0000739.pd

Chronic treatment with amitriptyline produces supersensitivity to nicotine,

The authors used a thermoregulation paradigm to evaluate effects of amitriptyline (AMI) on the sensitivity of a nicotinic mechanism involved in the regulation of core temperature in rats. Treatment with this tricyclic was associated with a significant increase in the hypothermie response to nicotine. Supersensitivity persisted for a minimum of 7.5 days following the last dose of AMI, and a significant proportion of animals displayed increased sensitivity after 14.5 days of abstinence. Implications for the mechanism of action of AMI are highlighted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27428/1/0000466.pd