The behavioural effects of intrathecally administered [D-PRO2, D-TRP7,9]-substance P, an analogue with presumed antagonist actions, in the rat

[D-Pro2, D-Trp7,9]-substance P, an analogue of the putative nociceptive primary afferent neurotransmitter substance P, was administered to rats via chronically implanted intrathecal catheters (0.5-2.5 nmol per rat). Several animals showed large elevations of thermal and mechanical nociceptive thresholds, but these effects were always accompanied by profound, often long-lasting, impairments of motor function and thus cannot be regarded as a specific antinociceptive effect of the drug. These behavioural effects are considered to be probably due to direct spinal actions of the drug rather than antagonism of spinal substance P systems.     

Pharmacological differentiation between responses of rat medullary dorsal horn neurons to noxious mechanical and noxious thermal cutaneous stimuli

Responses of lamina V medullary dorsal horn neurons to noxious thermal and noxious mechanical facial stimuli were challenged with iontophoretically appliedcis-2,3-piperidine dicarboxlic acid, a broad spectrum excitatory amino acid antagonist. This antagonist reduced neuronal responses to noxious mechanical stimuli but not responses to noxious thermal stimuli. These results suggest that different neural mechanisms underlie the responses of lamina V neurons to different noxious stimuli, and that responses to noxious mechanical stimuli appear to involve excitatory amino acid receptors.     

Pseudoaneurysms complicating organ transplantation: roles of CT, duplex sonography, and angiography

In a retrospective study of proved pseudoaneurysms (PAs) in 15 patients with transplanted organs (11 liver, three kidney, one pancreas), the results of computed tomography (CT), duplex sonography, and angiography were reviewed. Of the 15 cases of PA, eight occurred at the arterial anastomosis and seven were nonanastomotic. Three of the eight anastomotic PAs were caused by infection. Of the seven nonanastomotic PAs, four were caused by percutaneous biopsy, two were caused by infection, and one was of undetermined cause. In nine (60%) of the 15 patients the PAs were incidentally detected at imaging studies performed for other reasons. Diagnosis requires a high degree of suspicion. CT was performed in nine cases and duplex sonography in ten. The diagnosis of PA was made with CT in six (67%) patients and with duplex sonography in five (50%). CT and duplex sonography could not enable diagnosis when the PA was small, when the arterial anastomosis was not included in the field of study, or when enhancement with intravenously administered contract material was suboptimal. Angiography depicted the PAs in all 15 patients. In three liver transplant recipients with gastrointestinal tract bleeding, the causative PAs were detected only with angiography.     

Stress and adaptation in medical students: Who is most vulnerable?

There is concensus that medical school years are stressful but there has been little systematic investigation of the relationship between these stresses and manifestations of distress in the students. This paper reports results from the first wave of data in a longitudinal study of the physical and psychological health concomitants of the stresses of medical school. Two entering classes were surveyed by questionnaire in the fall of 1980. The number of recent life changes, degree of perceived stress, habits of nervous tension, depression, anxiety, and number of physical symptoms were among the variables measured. There were no significant sex or minority status differences in number or amount of perceived stresses. Moderate positive correlations were observed between level of stress and both psychological and physical distress. Few sex or minority status differences appeared. This diverse population of medical students showed a marked similarity in levels of stresses brought to the training period although there was some variation in the source of the stresses.     

Differential effects of benzodiazepines and amphetamine on exploratory behaviour in weanling rats: an animal model for anxiolytic activity

An animal behaviour model is described in which the exploratory activity of weanling rats in an area inaccessible to the mother rat is measured by ultra sound. The model distinguishes between benzodiazepines and amphetamine or desipramine when the drugs are given acutely to the weanlings. Flurazepam, nitrazepam, oxazepam and chlordiazepoxide produced a dose-dependent increase in exploratory behaviour and a reduction of activity at higher doses. Chronic administration of chlordiazepoxide in the diet of the maternal rat also produced an increased exploratory activity in the weanlings. Diazepam and oxazepam were without effect at the doses used. It is proposed that this model has value in assessing anxiolytic activity in acutely or chronically administered benzodiazepines.     

Distribution of substance P-responsive and nociceptive neurones in relation to substance P-immunoreactivity within the caudal trigeminal nucleus of the rat

Substance P is a peptide which is found in small diameter primary afferent fibres and may have a function in nociceptive afferent transmission. In order to study the role of substance P in sensory processes in depth, we have compared the distributions of nociceptive neurones and substance P-responsive neurones with the distribution of substance P in the caudal trigeminal nucleus of the rat. It was found that substance P-like immunoreactivity was located primarily in the superficial layers of nucleus caudalis (equivalent to laminae I and II of the dorsal horn) and in more ventromedially located areas (equivalent to laminae V and VI). The distribution was found to be in good agreement with the distribution of nociceptive neurones. Iontophoretically applied substance P had predominantly excitatory actions on both nociceptive and non-nociceptive nucleus caudalis neurones, although the peptide did appear to be slightly more likely to excite nociceptive neurones. Similarly, the peptide appeared slightly more likely to be excitatory in areas of nucleus caudalis showing substance P staining, but excitations were also predominantly seen in areas containing little or no apparent substance P staining. These results are consistent with the proposed role for substance P as a nociceptive afferent neurotransmitter. However, it is also possible that the peptide performs other functions in the processing of sensory information.     

The effects of capsaicin pre-treatment on the responses of single neurones to sensory stimuli in the trigeminal nucleus caudalis of the rat: Evidence against a role for substance P as the neurotransmitter serving thermal nociception

Rats were systemically pre-treated with capsaicin either on the first day of life or at an age of 1 month. Both treatments were found to deplete substance P levels in the trigeminal nucleus caudalis (55.6% and 57.9% depletions, respectively). Extracellular single neurone recordings in the trigeminal nucleus caudalis revealed that neither type of capsaicin treatment greatly altered the proportions of neurones responding to non-noxious or noxious mechanical stimulation of the face. However, the proportion of mechanically-nociceptive neurones also responding to noxious thermal stimulation was greatly reduced in neonatally-treated, but not adult-treated rats.As both methods of capsaicin treatment caused similar depletions of substance P, it is concluded that this peptide may not be the neurotransmitter of afferent fibres to the trigeminal nucleus caudalis signalling thermal nociception.