David I. Astrachan

Conditioned fear and startle magnitude: effects of different footshock or backshock intensities used in training.

In Experiment 1 four groups of rats received 30 light-shock pairings using footshock intensities of either .2, .4, .8, or 1.6 mA. One day later all rats were tested for startle by presenting tones in the presence or absence of the light CS. Potentiated startle (the difference between startle on light-tone vs tone-alone trials) was nonmonotonically related to the shock intensity used in training, with the greatest potentiation at intermediate shock levels. Experiment 3 demonstrated a similar relationship when backshocks instead of footshocks were used. In Experiment 2 rats were trained with either a moderate or high shock and then given an extended extinction-test session 1 day later. The moderate-shock group showed a gradual decline in potentiated startle over extinction. The high-shock group showed a nonmonotonic extinction curve where potentiation progressively increased toward the middle of extinction and dissipated thereafter. The results suggest that acoustic startle bears an inverted U-shaped relationship to fear and are discussed in relation to other studies concerned with this issue.

Prolonged intubation vs. tracheotomy: complications, practical and psychological considerations.

The charts of 52 adult patients who underwent tracheotomy (49 after intubation) were reviewed to identify early complications of both endotracheal intubation and tracheotomy. The complication rate of endotracheal intubation was 57%, and of tracheotomy, 14%. None of the complications of tracheotomy was serious.

Le fort i osteotomy approach to the skull base

Horizontal osteotomy allows the surgeon to safely down‐fracture the maxilla for wide exposure of the central skull base. This surgical approach is easily extended posteriorly in the midline to include the clivus and the arch of C1, providing 8 cm of horizontal anterior exposure and 5 cm of posterior. Wide operative exposure and a low rate of complications afford superior functional and cosmetic preservation in removing tumors of the central cranial base.

Spinal modulation of acoustic startle: Opposite effects of clonidine and d-amphetamine

Direct infusion of d-amphetamine (25–400 μg) or phenylephrine (12.5–50 μg) onto the spinal cord (intrathecal administration) increased acoustic startle amplitude. These effects were blocked by IP injection of the α1-adrenergic antagonist WB-4101, but not the serotonin antagonist cyproheptadine. In contrast, intrathecal administration of clonidine (0.9–12.5 μg) markedly depressed startle. This effect was not blocked by IP administration of WB-4101 or cyproheptadine, but was blocked by IP or intrathecal administration of the α2-adrenergic antagonist yohimbine (5 mg/kg), which by itself increased startle. Moreover, intrathecal yohimbine (100 μg) attenuated the depressant effect of IP clonidine, indicating that the spinal cord partially mediates the depressant effects on startle after systemic administration of clonidine. Thus clonidine does not behave like an α1-adrenergic on acoustic startle, even when introduced directly onto the spinal cord. Conditions under which clonidine produces excitatory or depressant behavioral effects are discused.

Behavior and binding: Correlations between α1-adrenergic stimulation of acoustic startle and α1-adrenoceptor occupancy and number in rat lumbar spinal cord

The relationship between alterations in alpha 1-adrenoceptors and behavioral effects of alpha 1-adrenergic agonists were investigated in a localized region of the rat central nervous system. Direct infusion of the alpha 1-adrenergic agonists, D-amphetamine or phenylephrine. into the subarachnoid space of the lumbar cord (intrathecal administration) increased the amplitude of the acoustic startle reflex, The magnitude of this behavioral facilitation correlated highly with the degree of alpha 1-adrenoceptor occupation measured by [3H]prazosin binding in lumbar spinal tissue. Using an in vitro estimate of receptor occupation, maximal potentiation of startle occurred following approximately 30% occupation of the receptors, using either D-amphetamine or phenylephrine. Intrathecal administration of 6-OHDA produced a 95% decrease in spinal norepinephrine and markedly enhanced the behavioral response to intrathecal phenylephrine as well as the number of alpha 1-adrenoceptors. The correlation between the time course of the behavioral and binding changes was 0.99. No change in receptor affinity (KD) or receptor occupation by phenylephrine was found after 6-OHDA. The data indicate that receptor binding parameters do have predictive value for behavior, especially if localized regions of the nervous system, critical to the behavior, are analyzed.

5-Methoxy-N,N-dimethyltryptamine: spinal cord and brainstem mediation of excitatory effects on acoustic startle.

The effects of different doses (0.03, 0.06, 0.12, 0.25, 1.0, 2.0, 4.0, and 8.0 mg/kg body weight) of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) were tested on the acoustic startle reflex in rats. Beginning at 0.12 mg/kg, 5-MeODMT increased startle monotonically up to the highest dose used. 5-MeODMT still increased startle in acutely decerebrate rats or when infused directly onto the spinal cord. The excitatory effects of a high systemic dose of 5-MeODMT were completely blocked by cinanserin, cyproheptadine, and propranolol, but not by parachlorophenylalanine, α-methyl-p-tyrosine, haloperidol, sotalol, or phenoxybenzamine. The results were discussed in terms of a new theory, which suggests that stimulation of serotonin receptors in the spinal cord enhance startle whereas serotonin receptors in the forebrain inhibit startle.

Stomal complications and airflow line problems of the Communi-Trach I cuffed talking tracheotomy tube.

There have been no reports of stomal complications and airflow line problems associated with a cuffed talking tracheotomy tube. However, the results of this study showed that stomal complications, in the form of pressure necrosis and wound extension, and problems with airflow line kinking occurred with a 40% and 80% frequency, respectively. Solutions to both difficulties arc discussed.

The effect of D-Lysergic Acid Diethylamide (LSD) upon shock elicited fighting in rats

Abstract The action of different doses of LSD on shock elicited fighting was tested in rats. A biphasic dose response was found with low doses facilitating fighting whereas a high dose had no effect. The results are discussed in terms of the effects of LSD on single units of the serotonin neuronal system.

Effect of noise on shock-elicited aggression in rats

ONLY a limited number of experiments have been designed to evaluate the effects of noise on aggression. As animal models of aggression are amenable to pharmacological and physiological analysis we have investigated the effect of noise on aggression in rats and have found an interesting non-monotonic relationship, with an increase in aggression at moderate noise levels but a decrease at high levels. The aggressive behaviour chosen for the present experiments was shock-elicited aggression in the rat. Two rats were paired in a small enclosure and subjected to a series of footshocks which elicit fighting, depending on the intensity, frequency and duration of electric shock1,2. This is a well documented and highly reliable form of aggressive behaviour that is usually considered a form of irritable aggression3.

Behavior and binding: desensitization to α1-adrenergic stimulation of acoustic startle is associated with a decrease in α1-adrenoceptor binding sites

Desensitization of the excitatory effects of α 1 -adrenergic agonists on acoustic startle occurred 6 h after intrathecal administration of the α 1 -adrenergic agonist, phenylephrine. This desensitization was associated with a decrease in α 1 -adrenoceptor sites in the lumbar spinal cord.