Search PubMed⌕ Search

Biomedical subjects

L D Byrd

Publications and source records attributed to L D Byrd.

At least 37 records · Page 2Linked to original sources
PubMed1985

d-Amphetamine induced changes in social interaction patterns.

The behavioral effects of d-amphetamine were studied in a group of stumptail macaques in a large outdoor enclosure. d-Amphetamine altered characteristic patterns of aggressive and affiliative behaviors in adult males that received the drug. Each monkey that received d-amphetamine increased its aggression toward non-adult animals in the group and decreased aggression toward adult members. In subjects for which genealogy was known, d-amphetamine increased aggression toward kin-related members of the group and decreased aggression toward non-kin monkeys. The effects of the drug on affiliative behaviors were less uniform and, therefore, less conclusive. Three subjects decreased affiliation and two increased affiliation toward non-adult monkeys. The results demonstrate that d-amphetamine can alter substantially the behavior of drug-treated members of a group and, in addition, that the drug can indirectly affect specific subsets of the group even though they did not receive the drug.

Aggression↗
PubMed1984

Contrasting effects of d-amphetamine on affiliation and aggression in monkeys.

Amphetamine has been observed to alter conditioned or learned behavior in individually housed animals, as well as naturally-occurring behavior characteristic of animals living in groups. This study is concerned with the effects of d-amphetamine on affiliative and aggressive behavior in adult male stumptail macaques (Macaca arctoides) living in a large, heterogeneous social group. Using standardized observational techniques, the affiliative and aggressive behaviors initiated by five adult male monkeys were characterized and quantitated in the absence of and following drug administration. Acute administration of a range of doses of d-amphetamine (0.003-0.56 mg/kg) resulted in a monotonically depressive effect on the rate of affiliative behavior initiated by the experimental animals. In contrast, d-amphetamine increased the rate of aggressive behavior initiated by the highest- and lowest-ranking monkeys, and had little or no effect in the mid-ranking monkeys. These results show that d-amphetamine can have qualitatively different effects on affiliative and aggressive behavior in the same subjects. The results also provide evidence that the effects of d-amphetamine can be determined by the hierarchical or dominance position of the subject in the group.

Aggression↗
PubMed1983

Cardiovascular effects of naloxone, naltrexone and morphine in the squirrel monkey.

Heart rate (HR) and mean arterial blood pressure (BP) were recorded from conscious, chair-restrained squirrel monkeys surgically prepared with chronically indwelling arterial and venous catheters to determine the effects of acute intravenous injections of two opiate antagonists and an agonist. Naloxone (0.3--10.0 mg/kg) or naltrexone (0.3--10.0 mg/kg) had little effect on HR or BP during a 30-minute post-injection period. Morphine (3.0--5.6 mg/kg) produced biphasic effects comprising an initial decrease followed by an increase in HR, and an increase followed by a decrease in BP. Lower morphine doses had lesser effects during a 100-minute post-injection period. Pretreatment with 0.03 mg/kg naloxone attenuated the depressive effect of morphine on HR and BP, but increases in HR and BP due to morphine were enhanced. Pretreatment with 0.3 mg/kg naloxone prevented morphine-induced decreases in HR and BP, yet increases in HR and BP persisted. In previous behavioral studies, morphine in combination with naloxone similarly increased rates of responding in the squirrel monkey. Together, these data suggest an effect of naloxone that goes beyond mere pharmacological antagonism of the effects of morphine.

Animals↗
PubMed1983

An interresponse-time analysis of responding maintained by schedules of response-produced electric shock.

The present study investigated ratio contingencies to evaluate factors that may determine the maintenance of responding when electric shock is the consequent event. Initially, squirrel monkeys (Saimiri sciureus) were exposed to a continuous-avoidance schedule to initiate bar pressing. Subsequently, a multiple random-interval variable-ratio yoked schedule of response-produced shock was used to maintain and to compare interval and ratio performance. A microcomputer recorded and stored the number of responses and interresponse times occurring between successive shock presentations during a given random-interval component, and these numbers determined the ratio requirements during the subsequent ratio component. Responding was maintained for more than 80 sessions in two of three monkeys under the multiple schedule with the ratio yoked to the interval component. Responding during the ratio component persisted in only one monkey, however, when the components were no longer yoked. An analysis of the interresponse times immediately preceding shock under the multiple yoked schedule revealed that the terminal interresponse times were longer under the interval schedule than under the ratio contingency. The interresponse-time analysis indicated that differential interresponse-time relationships may be major determinants of the maintenance of behavior controlled by schedules of electric-shock presentation.

Journal Article↗
PubMed1983

Effects of d-amphetamine on self-aggression and posturing in stumptail macaques.

The behavioral effects of d-amphetamine sulfate were studied in adult male stumptail macaques living within a large heterogeneous group in an outdoor enclosure. Among five subjects that received a range of doses (.01 to .3 mg/kg), d-amphetamine increased self-aggressive behavior and abnormal posturing in subjects that exhibited these types of behavior prior to drug administration, but it had no effect in subjects not exhibiting those activities in the absence of the drug. For the former subjects, the dose-effect curves for self-aggression were of an inverted U-shape analogous to the effect of d-amphetamine on schedule-controlled behavior. Over the range of doses studied, the curve for abnormal posturing was monotonic. The data indicate that d-amphetamine can have effects on untrained behavior in individual animals in a quasinatural environment that are qualitatively and quantitatively similar to the behavioral effects observed in other laboratory environments, and that d-amphetamine does not evoke or increase a behavioral response in individual subjects that do not exhibit the response in the absence of the drug.

Aggression↗
PubMed1981

Time-course effects of adrenergic and cholinergic antagonists on systemic arterial blood pressure, heart rate and temperature in conscious squirrel monkeys.

Mean arterial blood pressure, heart rate, and rectal temperature were measured from conscious, chair-restrained squirrel monkeys prepared with chronically indwelling arterial and venous catheters and temperature probes to determine the magnitude and duration of the effects of acute intravenous injections of propranolol, phentolamine and methyl atropine. The data indicate a predominant influence of the sympathetic nervous system in the regulation of cardiovascular activity resting squirrel monkeys.

Animals↗
PubMed1980

Magnitude and duration of the effects of cocaine on conditioned and adjunctive behaviors in the chimpanzee.

Characteristic patterns of conditioned key-pressing were maintained in the chimpanzee under a multiple 30-response fixed-ratio, 10-minute fixed-interval schedule of food presentation. Adjunctive drinking occurred with regularity during the fixed-interval schedule and, with less frequency, during 1-minute timeout periods that followed each food presentation; drinking seldom occurred during the fixed-ratio schedule. Cocaine increased key pressing under the fixed-interval schedule at doses between .1 and 3.0 mg/kg, but adjunctive drinking and key pressing under the fixed-ratio schedule did not increase at any dose. Conditioned and adjunctive behaviors were disrupted and suppressed for different durations at 10,0 mg/kg, a dose which induced convulsive seizures within 10 minutes after intramuscular injection. A time-course analysis showed the magnitude and duration of the effects of cocaine on key pressing under the fixed-interval schedule and on adjunctive drinking to be dose-related. Moreover, a given dose of cocaine had diverse effects, depending on the behavior and the time since drug administration.

Animals↗
PubMed1979

The behavioral effects of cocaine: rate dependency or rate constancy.

The behavioral effects of cocaine were studied in squirrel monkeys trained to press a response key under an 8-min fixed-interval (FI) schedule of electric shock presentation. Overall mean rate of responding increased at 0.03--0.3 mg/kg (i.m.) and decreased at 1.0--3.0 mg/kg. Increased responding during the initial and middle periods of the fixed-interval accounted for the increase in overall mean rate; response rate during the final two min of the interval did not increase at any dose. An analysis based on response rate during individual 1-min segments of the 8-min interval showed that the rate during the interval became more uniform, and the pattern of positively accelerated responding became more linear, as dose increased. At 0.3--1.0 mg/kg, response rate was relatively constant and independent of the control, pre-drug rate of responding.

Animals↗
PubMed1979

A tethering system for direct measurement of cardiovascular function in the caged baboon.

A device suitable for the continuous measurement of physiological activity in large, conscious monkeys has permitted the direct recording of systemic arterial blood pressure and heart rate in caged baboons. The device comprises a lightweight fiberglass backpack, retained in place on the baboon by a thoracic elastic band and shoulder straps, and a flexible stainless steel tether connecting the pack to an electrocannular slip-ring in the top center of the baboon's cage. A chronically indwelling arterial catheter inserted retrograde into the abdominal aorta via the internal iliac artery and connected to a small pressure transducer on the pack provides direct measurement of blood pressure and heart rate. Body fluids can be sampled or drugs administered via an indwelling catheter in the inferior vena cava. Electrical and fluid connections between the fiberglass pack and recording and infusion equipment located outside the cage pass through the flexible tether and remain protected from the subject. The reliability of the tethering system has been demonstrated in physiological, pharmacological, and behavioral experiments with baboons.

Animals↗
PubMed1977

Responding in the squirrel monkey under fixed-ratio schedules of stimulus termination.

Key pressing was maintained under a fixed-ratio schedule in which electric shock was scheduled for delivery at a fixed time (t seconds) after each stimulus onset, and every n(th) response terminated the stimulus and initiated a timeout from shock. Under this procedure, the higher the rate of responding, the briefer the duration of the stimulus presentation and the lower the frequency of shock delivery. The effects of several schedule parameters were studied to determine whether the maintenance of responding was dependent on an inverse relation between response rate and shock frequency. Shock rate and shock frequency were made independent of response rate by decreasing the value of t to 0.5 second and delivering shock only during the first presentation of the stimulus after a fixed time, including stimulus and timeout durations, had elapsed since the previous shock. The experiments showed that shock frequency and response rate are inversely related when t is of relatively long duration compared to the value of the fixed-ratio parameter, but that a decrease in shock rate or frequency due to a high rate of responding is not necessary for the maintenance of responding under a fixed-ratio schedule of stimulus termination.

Journal Article↗
PubMed1976

Effects of morphine alone and in combination with naloxone or d-amphetamine on shock-maintained behavior in the squirrel monkey.

Key-pressing behavior in the squirrel monkey was maintained under an 8-min fixed-interval (FI) schedule of electric-shock delivery. The acute i.m. administration of morphine prior to a daily session decreased response rates at doses of 1.0--3.0 mg/kg but had little systematic effect on rate at doses of 0.03-0.3 mg/kg. When naloxone was administered concomitantly with morphine prior to a session, 0.01 mg/kg naloxone required a three-fold increase in the dose of morphine necessary to obtain decreased response rates, 0.1 mg/kg naloxone required a 30-fold increase in morphine, and 1.0 mg/kg required more than a 30-fold increase in morphine. Moreover, the administration of naloxone with morphine resulted in increased rates of responding at certain combinations of doses of the two drugs. The administration of d-amphetamine (0.03 or 0.1 mg/kg) alone increased mean response rates under the FI schedule; when combined with 0.03-0.3 mg/kg morphine the increases in responding were greater than obtained with d-amphetamine alone. The negative slope of the linear regression lines relating the effects of morphine to control rates of responding engendered under the FI schedule was decreased when morphine was combined with naloxone, but not with d-amphetamine. These results show that naloxone, but not d-amphetamine, can antagonize the response-rate decreasing effect of morphine when responding in the squirrel monkey is maintained by response-produced electric shock.

Animals↗
PubMed1975

Contrasting effects of morphine on schedule-controlled behavior in the chimpanzee and baboon.

Schedule-controlled key pressing was maintained in two chimpanzees and three baboons under a multiple 10-minute fixed-interval (FI 10-min) 30-response fixed-ratio (FR 30) schedule of food delivery. Characteristic rates and patterns of responding were maintained under the FI and FR schedules, and the performance of the two species differed in no systematic way. The acute i.m. administration of morphine (0.1-3.0 mg/kg) prior to selected 2-hour sessions increased mean rates of responding under the FI schedule in the chimpanzee, but decreased responding in the baboon. At a dose of 3.0 mg/kg of morphine, responding under the FI schedule in the chimpanzee increased 4-fold and responding in the baboon decreased to less than 25% of control levels. Mean response rates under the FR schedule were also increased by morphine in the chimpanzee, but responding under the FR schedule was little affected in the baboon except at the higher doses which decreased response rates below control levels. Respiratory rate in the chimpanzee was markedly depressed at 5.6 mg/kg of morphine and one chimpanzee died. A similar depression of respiration was not observed in the increase responding in a nonhuman primate, the chimpanzee, and that the behavioral effects of morphine in the chimpanzee are qualitatively different from the effects in monkeys.

Animals↗