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Biomedical subjects

F E Bloom

Publications and source records attributed to F E Bloom.

At least 289 records · Page 16Linked to original sources
PubMed1981

Lithium treatment decreases blood pressure in genetically hypertensive rats.

Chronic lithium treatment was examined for effects on the blood pressure of spontaneously hypertensive rats (SHRs). Treated rats were allowed continuous access to a pelleted lithium diet (1.7 g LiCl (40 mmol)/kg diet) for 21 days. Control SHRs were fed a similar diet lacking the lithium. Two groups of control rats were examined. One group had continuous access to control diet (ad lib controls); a second group was pair-fed a daily ration of control diet such that their mean body weight remained similar to the lithium treated group (pair-fed controls). Heart rate, systolic, diastolic and mean arterial blood pressures were recorded on day 21 from freely moving conscious rats. Systolic, diastolic and mean arterial blood pressure was significantly lower (approximately 15 mmHg) in the lithium treated SHRs as compared to either control group; the pair-fed and ad lib controls had similar blood pressures at the end of the treatment periods. Heart rate was increased in the lithium treated animals. All rats gained weight during the 21 days of treatment, although the lithium treated group and the pair-fed control group did not gain weight as much or as rapidly as the control group that had continuous access to control diet. Plasma and brain lithium levels were in the moderate range (0.3--0.4 meq/l) and all rats appeared healthy at the end of the experiment. These results suggest that chronic treatment may have clinically relevant effects on blood pressure.

Animals↗
PubMed1981

The behavioural effects of enkephalin analogues injected into the ventral tegmental area and globus pallidus.

Two stable analogues of enkephalin D-Ala2-Met5-enkephalinamide (DAMA) and D-Ala2,D-Leu5-enkephalin (DADLE) injected bilaterally into the ventral tegmental area (VTA) induced locomotion, characterized by bursts of morphine-like activity. The response of DADLE was blocked by systemic-alpha-flupenthixol (0.2 mg/kg) and naloxone (1 mg/kg). At higher doses of enkephalins in the VTA, stereotypy behaviour involving gnawing, became apparent. When injected bilaterally into the globus pallidus (GP), both analogues induced a dose-dependent increase in locomotor activity but stereotypy was not observed. The locomotor behaviour induced by DADLE was blocked by naloxone but not by alpha-flupenthixol. These results suggest that naloxone-sensitive opiate receptors modulate, at a number of different sites, the neural pathways involved in the expression of behavioural activity.

Animals↗
PubMed1981

Adrenal steroid-induced changes in beta-adrenergic receptor binding in rat hippocampus.

Bilateral 6-hydroxydopamine (6-OHDA) lesions of the dorsal noradrenergic bundle have been shown to increase [3H]dihydroalprenolol (DHA) binding in the rat hippocampus. The effect of adrenalectomy on this increase in receptor binding was examined. Groups of rats received stereotaxically placed 6-OHDA injections aimed at the dorsal bundle (DB) or vehicle injections (control). Half of each group subsequently received bilateral adrenalectomies (ADX) and the other half received sham operations, yielding four groups: control, DB, ADX, and DB + ADX. The DB lesions produced a 41% increase in maximum binding in close agreement with a previous report. No statistically significant change in [3H]DHA receptor binding was observed following adrenalectomy treatment alone. By contrast, the DB + ADX group showed a significant increase in maximum [3H]DHA receptor binding compared to the DB group. This adrenalectomy-induced increase was reversed after 1 week of corticosterone treatment (1.0 mg/kg/12 h, s.c.). These results suggest an interaction between noradrenergic mechanisms and corticosterone in the hippocampus.

Adenylyl Cyclases↗
PubMed1981

Response artifact in the measurement of neuroleptic-induced anhedonia.

Systemic administration of the neuroleptic drug alpha-flupenthixol attenuated lever-pressing behavior in rats responding for rewarding brain stimulation. The magnitude of this attenuation was dose-dependent and resembled the effects of reward reduction and termination. However, when the operant response requirements of the same rats were changed to nose poking, identical drug treatments produced relatively little attenuation in performance. These data do not support the belief that neuroleptics produce a general state of anhedonia. Rather, the apparent suppression of reinforced behaviors depends at least in part on the kinetic requirements of the response.

Animals↗
PubMed1981

In vivo release of enkephalin from the globus pallidus.

Push-pull cannulae were acutely positioned through previously implanted guides in the globus pallidus of unanesthetized freely moving cats and rats. During slow-flow perfusions, enkephalin release was detected in resting conditions and increased more than 3-fold when both 50 mM K+ and 1.8 mM Ca2+ were present in the perfusing medium. Local perfusion with veratrine also enhanced enkephalin release. Furthermore, in vivo, electrical stimulation of the rat caudo-putamen enhanced enkephalin release in the pallidum. This latter finding is consistent with a functional strio-pallidal enkephalin-containing pathway previously postulated by immunohistochemical or lesion experiments.

Animals↗
PubMed1981

Golgi cells of the cerebellum are inhibited by inferior olive activity.

Golgi cells of the cerebellar cortex are inhibited by activation of the inferior olive by direct electrical stimulation, or by appropriate peripheral stimulation. The strength of the inhibition is correlated with the intensity of inferior olive activation. These results indicate that the olivocerebellar inhibition of Purkinje cells is probably not mediated by the Golgi cells, and suggest previously undetected effects of the inferior olive on cerebellar cortical information processing.

Animals↗
PubMed1981

Ethanol causes increases in excitation and inhibition in area CA3 of the dorsal hippocampus.

The effects of ethanol on synaptic transmission in hippocampus were studied by changes in the response of CA3 pyramidal cells to stimulation of two afferent pathways, the dentate (mossy fiber) pathway, and the commissural pathway. Both sources produce an excitatory response as measured either by single unit spiking or by population spike followed by a period of post-stimulus inhibition (PSI). After the injection of 3 g/kg ethanol (i.p.), both the excitatory responses and the duration of PSI are significantly increased. Because these changes occur in both afferent pathways, they are not pathway specific, but may be the result of the local microcircuitry in area CA3. Although the change in excitatory and inhibitory responses can occur simultaneously, detailed statistical analyses show that neither the magnitude nor onset times are correlated. Thus, the two responses are functionally separable. In addition, the increase in the duration of PSI is related to the rate of rise of blood ethanol level and shows short-term tolerance. The maximum change in the PSI occurs after blood ethanol levels plateau suggesting a secondary process is necessary before neurophysiological effects are apparent.

Animals↗
PubMed1981

Spontaneous activity in perfused hypothalamic slices: dependence on calcium content of perfusate.

We have established a totally-immersed, perfused slice preparation of the hypothalamus which is amenable for electrophysiological and pharmacological studies. The amount and pattern of spontaneous activity in the paraventricular nucleus (PVN) is markedly influenced by varying the amount of Ca++ in the oxygenated physiological medium which continuously perfuses the slice over both upper and lower surfaces. Ca++ concentrations greater than 1 mM virtually abolish spontaneous activity, although the neurons discharge in response to advance of the electrode and are activated by addition of glutamate to the perfusate. However, in a perfusing medium containing 0.75 mM Ca++, most cells display 1-7 Hz spontaneous activity for up to 10 h; some cells display phasic activity similar to that attributed to vasopressin neurons in vivo. Electrical stimulation peripheral to the PVN elicits antidromic potentials in some PVN neurons, sometimes followed by a post-activation depression of activity typical of recurrent inhibition. Under appropriate perfusion conditions, therefore, the hypothalamic slice preparation displays characteristics of the in vivo hypothalamus.

Animals↗
PubMed1981

Arginine vasopressin and a vasopressin antagonist peptide: opposite effects on extinction of active avoidance in rats.

Systemic injection or arginine vasopressin (AVP) (1 micrograms/rat) significantly prolonged extinction of a pole-jump, active avoidance response in rats; lateral ventricular injection of 1000-fold less AVP (1 ng/rat) produced similar results. A new AVP analogue, [1-deaminopenicillamine-2-(O-methyl)tyrosine]arginine vasopressin (dPTyr-(Me)AVP), is known to antagonize behavioral and vascular effects of exogenous AVP at molar ratios of 5 : 1. At a dose of 100 micrograms/rat (subcutaneously) dPTyr-(Me)AVP produces, by itself, a behavioral effect opposite to that of exogenous AVP, namely a facilitation of extinction. Injections of dPTyr-(Me)AVP into the lateral ventricle were ineffective except at a dose of 10 micrograms/rat. These results confirm previous reports of the effect of vasopressin on delaying extinction of avoidance behavior, but suggest a site of action distant from the lateral ventricle.

Animals↗
PubMed1981

Senescent pathology of cerebellum: Purkinje neurons and their parallel fiber afferents.

Two groups of naive male Sprague-Dawley rats, 5-7 and 24-26 months of age, were anesthetized with continuous intraperitoneal infusion of 4% chloral hydrate. Stimulation of the cerebellar vermis molecular layer permitted measurements of 12 different electrophysiological properties of parallel fiber Purkinje cell circuitry: parallel fiber conduction velocity, refractory period, threshold, and current dependent volley amplitude; slow negative wave threshold and current dependent amplitude; Purkinje cell activation threshold, latency, and current dependent spike driving; and Purkinje cell inhibitory threshold, latency, and current dependent duration of inhibition. Old subjects demonstrated deficits on all parameters except Purkinje cell inhibitory threshold. The relevance of these findings to our previous research on senescent changes in cell number, lipofuscin deposition, and spontaneous firing of Purkinje cells is discussed.

Afferent Pathways↗
PubMed1981

Neuropeptides.

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Angiotensin II↗
PubMed1981

Vasoactive intestinal polypeptide induces glycogenolysis in mouse cortical slices: a possible regulatory mechanism for the local control of energy metabolism.

Mouse cerebral cortex slices will synthesize [3H]glycogen in vitro. Vasoactive intestinal polypeptide (VIP) stimulates the enzymatic breakdown of this [3H]glycogen. The concentration giving 50% of maximum effectiveness (EC50) is 26 nM. Under the same experimental conditions norepinephrine also induces a concentration-dependent [3H]glycogen hydrolysis with an EC50 of 500 nM. The effect of VIP is not mediated by the release of norepinephrine because it is not blocked by the noradrenergic antagonist d-1-propranolol and is still present in mice in which an 85% depletion of norepinephrine was induced by intracisternal 6-hydroxydopamine injections. Other cortical putative neurotransmitters such as gamma-aminobutyric acid, aspartic acid, glutamic acid, somatostatin, and acetylcholine (tested with the agonist carbamylcholine) do not induce a breakdown of [3H]glycogen. This glycogenolytic effect of VIP and norepinephrine, presumed to be mediated by cyclic AMP formation, should result, at the cellular level, in an increased glucose availability for the generation of phosphate-bound energy. Given the narrow radial pattern of arborization of the intracortical VIP neuron and the tangential intracortical trajectory of the noradrenergic fibers, these two systems may function in a complementary fashion: VIP regulating energy metabolism locally, within individual columnar modules, and norepinephrine exerting a more global effect that spans adjacent columns.

Animals↗