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H C Fibiger

Publications and source records attributed to H C Fibiger.

At least 55 records · Page 3Linked to original sources
PubMed1978

Kainic acid lesions of the striatum dissociate amphetamine and apomorphine stereotypy: similarities to Huntingdon's chorea.

Kainic acid lesion of cell bodies in the dorsal striatum enhanced the stereotypy-producing effects of d-amphetamine without affecting the sterotypy produced by the direct receptor agonist apomorphine. This pattern of results parallels that found in patients suffering from Hungtington's chorea, thus strengthening the parallels between the kainic acid animal model and the human disease state initially suggested on biochemical gounds. The present results further suggest a dissociation of the mechanisms involved in the production of stereotypy by these two drugs, perhaps in terms of differential involvement of the striato-nigral negative feedback loop.

Animals↗
PubMed1978

The use of kainic acid in the localization of enzymes in the substantia nigra.

The selective destruction of neuronal perikarya via intracerebral injections of kainic acid was used to elucidate the cellular location of four neurotransmitter-related enzymes in the substantia nigra (SN). Two weeks after intranigral injections of kainic acid, dopamine-sensitive adenylate cyclase, glutamic acid decarboxylase (GAD), choline acetyltransferase (CAT) and acetylcholinesterase (AChE) were measured in the SN. Histological examination of the SN, and a reduction of striatal tyrosine hydroxylase (TH) activity by 94%, confirmed the extensive loss of neuronal cell bodies in the SN. Dopamine stimulation of adenylate cyclase was not reduced in the lesioned SN, supporting the view that dendritically-released dopamine can regulate cyclic AMP synthesis in afferent terminals to these dendrites. Nigral GAD activity was significantly reduced by the lesions, suggesting that there are GAD-containing perikarya in the SN. CAT activity was not affected by the kainic injections, indicating the absence of cholinergic perikarya in the SN. Nigral AChE activity was significantly decreased after kainic injections, thus confirming the presence of AChE within the nigral perikarya. The results suggest that dopamine-sensitive adenylate cyclase and CAT are located within afferents to the SN, while GAD and AChE are found, to some extent at least, in neuronal soma of the SN. The differentail effects of kainic acid on these enzymes suggest that this compound may be a useful neurochemical tool with which to determine the cellular distribution of enzyme systems in the central nervous system.

Acetylcholinesterase↗
PubMed1978

An analysis of dorsal and median raphe self-stimulation: effects of parachlorophenylalanine.

The role of serotonergic systems in intracranial self-stimulation (ICSS) of the dorsal and median raphe nuclei of rats was investigated. Intragastric administration of 400 mg/kg of parachlorophenylalanine (PCPA) depressed ICSS rates in the group with dorsal raphe electrode placements over a similar time course to the depletion of brain serotonin which results from treatment with PCPA. An intrasessional analysis of these behavioral changes on the fourth day after PCPA revealed that dorsal raphe ICSS was depressed over both halves of the 2 hr test session, whereas a significant depression in median raphe ICSS occurred only in the last hr of the session. The data from these studies suggest that brain serotonin systems contribute to the phenomenon of brain-stimulation reward in the dorsal and median raphe nuclei. The involvement of multiple neurochemical substrates of brain stimulation reward is discussed.

Animals↗
PubMed1978

Noradrenaline and partial reinforcement in rats.

Lesions of the dorsal nonadrenergic bundle produced by 6-hydroxydopamine, which depleted telencephalic noradrenaline by over 95%, were found to produce resistance to extinction in animals trained on a continuously reinforced schedule for food reward but not to alter the extinction rate after partial reinforcement training. These results confirm the dorsal bundle extinction effect reported previously but suggest that it is confined to continuously reinforced situations. The pattern of results is consistent with a role for the dorsal bundle in attentional processes but appears to contradict the predictions required if the dorsal bundle were to have a role in frustrative nonreward.

Animals↗
PubMed1978

The effects of dorsal bundle injections of 6-hydroxydopamine on avoidance responding in rats.

1 The effect of injection of 6-hydroxydopamine (6-OHDA) into the fibres of the dorsal noradrenergic bundle on acquisition, retention and extinction of active avoidance in rats were examined. 2 6-OHDA injections severely depleted noradrenaline in all forebrain areas assayed, with the interesting exception of the septum. No significant effect on dopamine concentrations in various forebrain regions was found. 3 Acquisition and retention of active avoidance was not altered by the lesion. Marked resistance to extinction was seen when the unconditioned stimulus (shock) was removed. 4 A comparison with work by other authors in which both forebrain noradrenaline and dopamine were depleted suggest that the alteration in extinction seen in both studies is a noradrenergic effect, whereas the deficits in acquisition and retention found previously are dopaminergic in origin.

Animals↗