A comparison of the effects of morphine on 5-HT metabolism in the periaqueductal gray, ventromedial medulla and medullary dorsal horn: in vivo electrochemical studies in freely moving rats.

The effect of systemic morphine on serotonin (5-HT) metabolism within the dorsal raphe nucleus (DRN) has been investigated by in vivo 5-hydroxyindole electrochemical (peak '3') detection in freely moving rats. Morphine caused a weak and delayed, but naloxone-reversible, increase in peak '3'. This increase was poorly, if at all, correlated with the morphine-induced analgesia.

In vivo electrochemical detection of 5-hydroxyindole within the trigeminal nucleus caudalis of freely moving rats: the effect of morphine.

The trigeminal nucleus caudalis is considered the equivalent of the orofacial nociceptive system of the dorsal horn of the spinal cord. At the level of this trigeminal area (i.e.

Morphine increases 5-HT metabolism in the nucleus raphe magnus: an in vivo study in freely moving rats using 5-hydroxyindole electrochemical detection.

The purpose of this study was to evaluate in freely moving animals the effect of morphine on the 5-hydroxyindole oxidation current recorded in the nucleus raphe magnus (NRM) which is the origin of serotonergic control systems modulating the transmission of noxious inputs at the spinal level. A current recorded at 270-290 mV (peak 3), characteristic of 5-hydroxyindoleacetic acid (5-HIAA), was measured with treated multi-fiber carbon electrodes, using differential pulse (DPV) or differential normal pulse (DNPV) voltammetry. In control rats the amplitude of the peak remains constant for many hours.

The mesencephalic locomotor region in cat: effects of local applications of diazepam and gamma-aminobutyric acid.

In decorticate unanaesthetized cats, displaying sequences of stereotyped locomotor movements in response to electrical stimulation of their footpad, local injections were made into the mesencephalic locomotor region (MLR). Diazepam (at 10 micrograms) and GABA (at 500 micrograms) induced complete suppression for 5-10 min, followed by partial amplitude recovery. It is suggested that: (i) MLR contains both diazepam and GABA receptors, and (ii) diazepam (and GABA) blockade is only short lasting because of a substitution (vicariancy) process through other structures also involved in locomotion.

In vivo electrochemical detection of 5-hydroxyindoles in rat cerebral cortex and spinal cord: differential effects of p-chloroamphetamine, probenecid and clorgyline.

Differential pulse voltammetry associated with carbon fiber microelectrodes was used to detect the 300 mV signal which is known to reflect the concentration of 5-hydroxyindoles in the spinal cord and cerebral neocortex of rats anesthetized with urethane or chloral hydrate. The intraperitoneal injection of p-chloroamphetamine resulted in an increase in the amplitude of the signal in the neocortex but not in the spinal cord. Administration of clorgyline did not consistently modify the signal monitored in the neocortex whereas it decreased in the spinal cord.

In vivo electrochemical detection of 5-hydroxyindoles in rat somatosensory cortex: effect of the stimulation of the serotonergic pathways in normal and pCPA-pretreated animals.

Differential pulse voltammetry was used for the detection of 5-hydroxyindoles in the cerebral cortex of rats anaesthetized with urethane. The stimulation of the lateral hypothalamus or of the dorsal raphe nucleus induced a 10-40% increase in the amplitude of the signal. The signal recorded from p-chlorophenylalanine (pCPA)-pretreated animals was much smaller than in normal animals and could be increased by 5-HTP administration.

Laminar distribution of serotonergic innervation in rat somatosensory cortex, as determined by in vivo electrochemical detection.

In vivo differential pulse voltammetry was used for the detection of indoleamines during vertical electrode penetrations in rat first somatosensory cortex, for studying the laminar distribution of serotonin and/or its metabolites in that part of the cortex. The peak of current corresponding to 5-hydroxyindoles was maximum in the most superficial part of the cortex and diminished gradually in the deeper layers. These results suggest that the cortical serotonergic innervation is predominant in the superficial layers.

Effects of thioproperazine and sulpiride on the locomotor rhythms in the decorticate cat.

The decorticate cat develops sequences of locomotor movements, especially in the two posterior limbs: those appear either spontaneously, or following a single shock applied to L7 dorsal root. Using this preparation, we tested the effects of two neuroleptic agents, Thioproperazine (TZ) and Sulpiride (S), through either systemic administration or local injection into the lateral-posterior hypothalamus and into the lumbar spinal cord. TZ administered i.

[Neurophysiological study in the cat of 2 substituted benzamides : sulpiride and sultopride].

Using three distinct electrophysiological tests in unanesthetized cat preparations (hippocampal theta, " caudat spindles " and stereotyped hind limb locomotor rhythms) two psychotropic benzamide derivatives (Sulpirid and Sultoprid) were tested both through systemic administration and local intracerebral microinjections. Our conclusions are that : a) Sulpirid activates the limbic system and locomotor rhythms, while deafferenting the higher " telodiencephalic " structures ; b) Sultoprid is, in revanche, at the same time deafferenting higher structure and depressing the lower one; c ) the hypothalamus represents one of the preferential targets for action of these substances.