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K A Bonnet

Publications and source records attributed to K A Bonnet.

At least 19 recordsLinked to original sources
PubMed1997

A parametric study of the N40 auditory evoked response in rats.

BACKGROUND: The N40 auditory evoked potential (EP) in rats is used to study "sensory gating." Our first goal was to compare the effects of systematically varying the characteristics of the pairs of clicks (S1-S2), on the degree of attenuation of the responses to S2 stimuli. A second goal was to examine the effects of changing S2 stimuli on the degree of attenuation of the responses to the deviant stimulus. METHODS: The N40 EP was recorded from 10 rats in eight identical-pair conditions and from 11 rats in two paradigms: nonidentical pairs and short trains of identical stimuli followed by a deviant stimulus. RESULTS: In eight identical-pair conditions changing stimulus duration, intensity, or frequency had no effect on the degree of attenuation of S2 responses. Changing S2 stimulus or presenting a deviant stimulus following a train of identical stimuli had a significant effect on the degree of attenuation of the response to the deviant stimulus. CONCLUSIONS: We conclude that the rat N40 EP is sensitive to stimulus change and can contribute to the study of both habituation and dishabituation mechanisms of "sensory gating."

Acoustic Stimulation↗
PubMed1990

The effect of hyperthyroidism on opiate receptor binding and pain sensitivity.

This study was conducted to determine the effect of thyroid hormone on opiate receptor ligand-binding and pain sensitivity. Specific opiate receptor-binding was performed on brain homogenates of Swiss-Webster mice. There was a significant increase in 3H-naloxone-binding in thyroxine-fed subjects (hyperthyroid). Scatchard analysis revealed that the number of opiate receptors was increased in hyperthyroid mice (Bmax = 0.238 nM for hyperthyroid samples vs. 0.174 nM for controls). Binding affinity was unaffected (Kd = 1.54 nM for hyperthyroid and 1.58 nM for control samples). When mice were subjected to hotplate stimulation, the hyperthyroid mice were noted to be more sensitive as judged by pain aversion response latencies which were half that of control animals. After morphine administration, the hyperthyroid animals demonstrated a shorter duration of analgesia. These findings demonstrate that thyroxine increases opiate receptor number and native pain sensitivity but decreases the duration of analgesia from morphine.

Animals↗
PubMed1985

Dopaminergic supersensitivity follows ferric chloride-induced limbic seizures.

Injection of ferric chloride (FC) into the left amygdala of rats produced limbic seizures that lasted at least 3 weeks. In addition, FC-injected animals demonstrated motor impairment, decreased protesting vocalizations, and spontaneous stereotypies during a behavioral examination. An increase in apomorphine-induced stereotypies was also noted, and weekly administration of apomorphine for 3 weeks potentiated the increase in stereotypies produced by FC injection. These behavioral changes were associated with changes in postsynaptic dopamine D2 receptors. In animals injected only with FC, an increase in the [3H]-spiperone Bmax in the left nucleus accumbens and an increase in Kd in the right nucleus accumbens were noted. In FC-injected animals challenged weekly with apomorphine for 3 weeks, increases in the [3H]-spiperone Bmax in both amygdalae, the left nucleus accumbens, and the right nucleus caudatus and increases in Kd in the left amygdala and right nucleus accumbens were noted. Severance of the anterior commissure at the time of FC injection reversed most of these changes in behavior and dopamine receptor binding. Possible mechanisms for these changes are discussed, as well as the implications of these results for research on limbic dysfunction and psychopathology.

Aggression↗
PubMed1983

Dopaminergic supersensitivity at distant sites following induced epileptic foci.

Injection of ferric chloride (FeCl3) into the left amygdaloid nucleus of the rat produced partial complex seizures. Subsequent repeated apomorphine challenges revealed steady development of behavioral dopaminergic supersensitivity, above that observed in saline-injected controls. The behavioral supersensitivity observed in FeCl3-injected animals was accompanied by increases in 3H-spiroperidol binding in contralateral amygdala, striatum and ipsilateral nucleus accumbens. In contrast, saline-injected controls demonstrated bilateral decreases in 3H-spiroperidol binding in amygdala and striatum. The effects of FeCl3 injection on the behavioral dopaminergic supersensitivity and 3H-spiroperidol binding were eliminated when the anterior commissure was severed.

Amygdala↗
PubMed1982

Mu and kappa opioid agonists elevate brain stimulation threshold for escape by inhibiting aversion.

Rats were trained to press a lever to escape electrical stimulation of the nucleus reticularis gigantocellularis and to obtain stimulation of the lateral hypothalamus. Morphine sulfate and ethylketocyclazocine (EKC) both elevated the intensity of stimulation required to sustain escape at doses which did not affect self-stimulation. Parallel dose-response lines were obtained for the two opioid agonists but the effect of EKC was more resistant to naloxone antagonism. These results suggest that both mu-and chi-sub-types of opiate receptor mediate the inhibition of supraspinally-elicited aversion.

Animals↗
PubMed1982

Brain cyclic AMP and memory in mice.

A phosphodiesterase inhibitor 4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone (Rolipram, 10 mg/kg IP) administered immediately, but not 3 hr post-training, reversed an amnesia for an inhibitory avoidance response induced by the protein synthesis inhibitor anisomycin. Immediate post-training administration of Rolipram also enhanced retention for a weakly learned avoidance response. Unshocked animals did not show increased test latencies thus ruling out conditioned aversion as an explanation for the enhanced avoidance. Mice treated with Rolipram (10 mg/kg after training showed elevated cyclic AMP but not cyclic GMP in frontal cortex, thalamus, and hypothalamus. These results support the suggestion that cyclic AMP may play a role in memory processes.

Animals↗