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R D Cox

Publications and source records attributed to R D Cox.

At least 73 records · Page 4Linked to original sources
PubMed1980

Phencyclidine-induced rotation and hippocampal modulation of nigrostriatal asymmetry.

Phencyclidine (PCP) elicited dose-related rotation in naive rats. The effect of PCP was consistent in direction and magnitude from one week to the next but was dissimilar to the rotatory effects of dopaminergic (D-amphetamine, apomorphine) or anticholinergic (scopolamine) drugs. Study of the effects of PCP on regional brain uptake of labeled 2-deoxy-D-glucose suggested that PCP-induced rotation is at least in part mediated by an action in the hippocampus. PCP elicited ipsilateral rotation following unilateral hippocampal lesions whereas such lesions did not alter the direction of either nocturnal or D-amphetamine-induced rotation. PCP appears to activate a hippocampal mechanism that normally only modulates the intensity of rotation.

Animals↗
PubMed1980

Intraperitoneal administration and other modifications of the 2-deoxy-D-glucose technique.

Experiments were conducted to determine the optimal conditions necessary for implementing modifications of the 2-deoxyglucose (2-DDG) technique. Substitution of tritium-labeled 2-DDG with subsequent microdissection of selected brain regions and liquid scintillation counting produced results that were highly correlated with both [14C]radioautograms and glucose utilization values as obtained by Sokoloff et al. The route of administration of isotope was also varied. Whole brain uptake at maximal levels of incorporation was the same for both intravenously and intraperitoneally injected animals. Radioautograms from i.p. and i.v. injected animals were indistinguishable. Densitometric analyses of the i.p. radioautograms were highly correlated with glucose utilization values. Thus, relative indices of functional activity may be obtained when experimental circumstances preclude arteriovenous cannulations and restraint. The use of naive, unrestrained animals, therefore, makes the 2-DDG technique applicable to a broader range of studies.

Animals↗
PubMed1979

Anticholinergic behavioral effect of phencyclidine.

Phencyclidine (PCP) impaired spatial alternation performance in rats. This effects was mimicked by antimuscarinic anticholinergics (scopolamine, atropine) and PCP derivatives (ketamine, cyclohexamine) but not by a variety of other agents. Muscarinic cholinergic agonists antagonized PCP. Impairment of spatial alteration performance by PCP appears to be mediated, at least in part, by and anticholinergic action; this is the first instance of a behavioral effect of PCP that can be largely attributed to a specific mechanism.

Animals↗
PubMed1978

Nocturnal rotation in normal rats: correlation with amphetamine-induced rotation and effects of nigrostriatal lesions.

Normal unoperated rats were observed to rotate (turn in circles) at night. For most (91.7%) rats, the preferred direction of rotation was consistent across hours and days and was the same as the direction of rotation elicited by D-amphetamine (1.0 mg/kg) during the day. The magnitudes of nocturnal and D-amphetamine-induced rotation were also highly correlated. After rats showed stable diurnal patterns of rotation, unilateral lesions were made in either the substantia nigra, the nigrostriatal bundle or the caudate nucleus. All lesions produced transient contralateral rotation within the first 24-48 h after surgery. The time-course of this contralateral rotation was more prolonged after nigral lesions than after nigrostriatal bundle lesions and least after caudate lesions, suggesting that the duration of a degeneration release of dopamine is proportional to the length of the degenerating axon. Lesion size was correlated with the intensity of contralateral rotation but not with the time-course. At each rostralcaudal level, the magnitude of contralateral rotation was greater if the lesion was in the side of the brain opposite to the preoperative direction of rotation than if in the same side. By three days after surgery, all rats returned to a mostly normal diurnal cycle with the direction of rotation now being ipsilateral to the lesion. D-Amphetamine potentiated the ipsilateral rotation, though rats with lesions in the same side of the brain as the preoperative direction of rotation had larger drug responses than rats with similar lesions in the opposite side of the brain. By one month after surgery, the direction of spontaneous rotation of most rats had returned to the preoperative direction. As at all other times, the magnitude of rotation was, in part, dependent on the side of the lesion with respect to the preoperative bias. It is suggested that, following a unilateral lesion, compensatory processes occur to a greater extent if the lesion is in the normally more active side of the brain.

Animals↗
PubMed1978

Changes in morphine self-administration after tel-diencephalic lesions in rats.

Rats were trained to bar-press for intravenous infusions of morphine sulfate during 1-h daily test sessions. Rates of morphine self-administration were enhanced by lesions of the frontal cortex and hippocampus and transiently reduced by lesions of the medial forebrain bundle and medial thalamus. Dose-response studies indicated that sensitivity to morphine's rewarding property was decreased by frontal cortical and hippocampal lesions. Lesions of the posterior cortex, the tuberculum olfactorium, and the nucleus accumbens had no effect on self-administration behavior. The results are discussed in relation to previous findings with caudate and brainstem lesions. A neuroanatomical substrate for morphine reinforcement is suggested.

Animals↗
PubMed1977

Changes in morphine self-administration after brainstem lesions in rats.

Rats were trained to bar press for intravenous infusions of morphine sulfate during 1-h daily test regions. Rates of morphine self-administration were reduced by bilateral lesions of the substantia nigra and enhanced by lesions of the medial raphe nucleus. Dose-response studies indicated that sensitivity to morphine's rewarding property was increased by substantia nigra lesions and decreased by medial raphe lesions. Lesions of the dorsal raphe nucleus and of the locus coeruleus had no effect on self-administration behavior. An interaction between ascending dopaminergic and serotonergic pathways appears to be involved in the mechanism of morphine reinforcement.

Animals↗
PubMed1977

Changes in sensitivity to operant effects of dopaminergic and cholinergic agents following morphine withdrawal in rats.

Rats trained to bar-press on either a FI 15 sec or FR 30 schedule for water reinforcement were administered various doses of appomorphine, haloperidol, pilocarpine and scopolamine both before and 1--4 months after a 3-day period of continuous morphine administration. All drugs monotonically depressed response rates on both schedules with increasing dose. Chronic morphrine administration produced a persistent increase in sensitivity to apomorphine and pilocarpine and a persistent decrease in sensitivity to haloperidol and scopolamine. The results suggest that both dopaminergic and cholinergic supersensitivity are likely to be involved in protracted abstinence phenomena.

Animals↗
PubMed1977

Pre- and post-synaptic actions of apomorphine: differentiation by rotatory effects in normal rats.

Normal rats were tested for rotation (circling behavior) following d-amphetamine (1.0 mg/kg) and, a week later, following apomorphine (10.0 mg/kg). In most rats, d-amphetamine and apomorphine elicited rotation in opposite directions whereas, in some rats, the two drugs elicited rotation in the same direction. Subsequently, alpha-methyl-p-tyrosine was found to antagonize the rotatory effect of apomorphine in the latter but not in the former rats. The results suggest that apomorphine has both pre- and post-synaptic actions and that relative sensitivity to these actions varies among rats.

Animals↗
PubMed1976

Differential effects of unilateral and bilateral caudate lesions on side preferences and timing behavior in rats.

Rats were trained to bar press on a differential-reinformcement-of-low-rate 16-sec (DRL 16) schedule for water reinforcement. On alternate days, rats were tested in the presence or absence of a light that signaled the availability of reinforcement. Rats were allowed to bar press on either of two levers (left and right). All rats showed consistent side preferences. For the non-signaled condition but not for the signaled condition, normal baseline rates were related to the strength of side preferences; lower rates and better timing performance were significantly correlated with greater preferences. Unilateral lesions in the caudate nucleus ipsilateral to side preferences facilitated timing performance during nonsignaled test sessions and increased side preferences during both nonsignaled and signaled sessions. Unilateral caudate lesions contralateral to side preferences impaired timing performance during nonsignaled test sessions and decreased side preferences during all sessions. Bilateral caudate lesions transiently depressed response rates without significantly affecting timing performance or side preferences. It is suggested that side preferences are intimately involved in the control of behavior by internal stimuli and that an inherent asymmetry in nigrostriatal function underlies side preferences; the effect of a unilateral striatal lesion will depend upon whether the lesion is placed in the more or less active striatum.

Animals↗
PubMed1975

Drusen of the iris: in advanced malignant choroidal melanoma.

Drusen were found in the iris between the layers of the pigment epithelium and the dilator muscle in an eye of a 52 year old patient that contained a large malignant choroidal melanoma. The significance of this unusual observation in comparison to the common drusen of Bruch's membrane of the choroid is discussed.

Choroid Neoplasms↗
PubMed1975

Relationship of rats' spatial preferences to effects of d-amphetamine on timing behavior.

Rats were trained to bar-press on a differential reinforcement of low rate 16 sec (DRL 16) schedule for water reinforcement. On alternate days, rats were tested in the presence or absence of a light which signaled the availability of reinforcement. Rats were allowed to bar-press on either of two levers (left and right). All rats show consistent side preferences. Doses (0.5-2.0 mg/kg) of damphetamine differentially affected performance under signaled and nonsignaled conditions. Performance during the nonsignaled condition was much more sensitive to a drug-induced rate increment and timing impairment than performance during the signaled condition. With increasing drug dosage, under both conditions, side preferences reliably increased, decreased or remained unchanged depending upon the particular pattern of paw usage and the relationship between paw and side preferences. For the nonsignaled condition but not for the signaled condition, baseline rates were related to the strength of side preferences; lower rates and better timing performance wwere significantly correlated with greater preferences. Observations of bar-pressing behavior suggested that stereotyped motor patterns associated with side preferences might be related to mechanisms involved in timing behavior and perhaps, in behavior controlled by internal stimuli generally.

Animals↗
PubMed1975

Dopaminergic and cholinergic influences on morphine self-administration in rats.

Various doses of apomorphine, haloperidol, pilocarpine and scopolamine were administered i.p. to rats self-administering i.v. morphine (0.4 mg/kg/infusion). Apomorphine, at low doses, increased rates of morphine self-administration and, at high doses, decreased rates. Haloperidol decreased self administration rates with increasing dose. Both pilocarpine and scopolamine produced only small decreases in rates at high doses. When administered in combination, the effects of apomorphine and haloperidol were antagonistic as were the effects of pilocarpine and scopolamine; the effects of apomorphine or haloperidol predominated, however, when either drug was administered in combination with pilocarpine or scopolamine. The results are consistent with previous work implicating an important role for dopaminergic mechanisms in morphine's reinforcing property.

Animals↗