Pushpa Deshmukh

A survey of substance P, somatostatin, and neurotensin levels in aging in the rat and human central nervous system ☆

Levels of the neuropeptides substance P, somatostatin, and neurotensin were measured by radioimmunoassay in regions of the rat and human central nervous system (CNS) in aging. Somatostatin levels were significantly lower only in the corpus striatum of older rats. Substance P levels and neurotensin levels were generally stable with aging as were levels of somatostatin in regions other than the corpus striatum. In post-mortem human CNS tissues, no significant negative correlations of levels of the three peptides were observed with time to refrigeration or time to freezer for the samples. In the human CNS, there were no significant age-related alterations in substance P levels in frontal cortex, thalamus, hypothalamus, caudate nucleus, globus pallidus, or substantia nigra. There was a significant age-related decrease in substance P levels in the human putamen. This age-related decrease was not present in tissues from victims of Huntingtons disease nor was there any striking difference in substance P levels as a function of duration of the disease. There were no significant age-related changes in somatostatin levels in human frontal cortex, caudate nucleus, putamen, medial globus pallidus, or substantia nigra. Among these same regions, there was a significant age-related decrease in neurotensin levels only in the pars compacta and pars reticulata of the human nigra. These, results implicate neuropeptides in aging processes in certain regions of the CNS. There are differences between rats and humans with respect to neuropeptides in the aging process in the CNS. Deterioration of some neuropeptide pathways in and to human basal ganglia may be involved in the suspected functional deterioration of parts of the extrapyramidal system in aging.

Computer-assisted autoradiographic localization of subtypes of serotonin1 receptors in rat brain

In vitro light microscopic receptor autoradiography was carried out to localize two subtypes of 5-HT1 receptors in certain regions of the rat central nervous system (CNS). The data were analyzed by computerized digital image processing to reveal subfields of high receptor densities within the septal area, the prefrontal and frontal cortex, and the hippocampus. The septum and hippocampus showed interesting localization of serotonin binding which can be subtyped into 5-HT1-A and 5-HT1-B sites. The differential localization of these sites may be helpful in shedding some light as to the functional significance of multiple serotonin receptors.

Thermal analgesia and substance P depletion induced by capsaicin in guinea-pigs

Abstract Treatment of adult guinea-pigs with subcutaneous doses of capsaicin of 1, 5, 50, 200, 200, 500, 500 mg/kg in daily succession increased skin flinch latency and depleted substance P from dorsal root ganglia. Similar treatment of animals with doses of 50, 100, 100, 100, 100 mg/kg significantly increased skin flinch latency and hot-plate escape latency and depleted substance P from dorsal root ganglia and dorsal spinal cord. Capsaicin had no effect on levels of substance P in other CNS regions or in any region of the gastrointestinal tract. Responses to mechanical pressure were not altered by capsaicin treatment. Depletion of primary afferent substance P in guinea-pigs appears to result in substantial thermal antinociception without producing comparable pressure antinociception.

Differences between rats and guinea pigs in gastrointestinal and nervous system substance P levels

Abstract Substance P immunoreactivity was measured in regions of the gastrointestinal and nervous systems of age-matched adult rats and guinea pigs. Guinea pigs were found to have substantially higher substance P levels than rats in the gastrointestinal system, in dorsal roots and ganglia, and in dorsal spinal cord. Rats had higher levels in hypothalamus while levels in corpus striatum and ventral spinal cord were comparable in both species. Treatment of guinea pigs with parenteral capsaicin reduced substance P levels only in dorsal roots and ganglia and in dorsal spinal cord.

A non-equilibrium 24-hour vasopressin radioimmunoassay: development and basal levels in the rat brain

Immunocytochemical studies, localizing vasopressin (AVP) within the neurohypophyseal system and in the CNS, paved the way for quantification of this peptide 2,3,23,25. Subsequently, concentrations of arginine vasopressin (AVP) in neural tissue have been measured by radioimmunoassay ( R I A ) 6,83°-12,15,2°,21. Earlier studies reported AVP levels in plasma, urine and cerebrospinal f l u i d 1,7,1236-18,22. Sensitivity of the RIAs utilized in these studies ranged from 0.1 to 4.0 pg of AVP 12,15, while the incubation times varied from 2 days (using a double antibody technique) to 5 and 7 days 12,15-28. While these techniques are generally useful for measuring low levels of AVP, we found it difficult to produce equilibrium assays with a detectable level below 1.0 pg AVP. We are interested in investigating extrahypothalamic vasopressin which is present in femtomole to picomole quantities 6,8,1°,JI,2~. In at least two studies 3,18, it was reported that AVP levels were below the detection of presently utilized AVP assays. Therefore, we examined the possibility that a rapid, non-equilibrium RIA, which would increase the sensitivity of d e t e c t i o n 9,19,22, could be applied to measure this psychologically relevant neuropeptide 5,~3,~4,24. In this paper we report a highly sensitive nonequilibrium RIA which can be performed within 24 h. To demonstrate the sensitivity of this RIA, brain regions from rat were examined for vasopressin content. Known amounts of synthetic vasopressin (Calbiochem-Behring) were serially diluted from 100 pg to 0.1 pg in 50 mM Na+/K + phosphate buffer containing 0.1% bovine serum albumin and 0.05% sodium azide, pH 7.4. A 50/~1 aliquot of a 1:7500 dilution of vasopressin antiserum (AVP-Ab; Calbiochem-Behring) or a 50/~1 aliquot ofa 1:75,000 dilution of AVP-Ab (gift of D. A. Fisher) was added to each 10 × 75 mm disposable glass tube. Following the preincubation period, approximately 10,000 cpm of [12q]AVP (50/~1, Calbiochem-Behring; spec. act. 2200 Ci/mmol) was added to each tube. Two control tubes, one containing antiserum and [1251]AVP and the other containing only [125I]AVP were included for estimates of maximum binding achieved and for separation effectiveness, respectively. Final assay volume was 300/~1. All assays were performed in duplicate. Bound [125I]AVP was separated from free [I25I]AVP by the addition of 500/~1 of dextrancoated charcoal. Assay tubes were then vortexed, incubated at 0-4 °C for 15 min and centrifuged at 1500 × g for 15 rain (Beckman TJ6). The supernatant was counted in a gamma counter (Tracor Model 1197 gamma counter; Eft. = 85%). The percent of maximum bound (bound/max bound) [I25I]AVP was plotted against

In vitro inhibition of vasopressin release in brain by behaviorally relevant ethanol concentrations

We have investigated the effect of ethanol upon vasopressin (AVP) content in brain and upon in-vitro release of AVP from the rat median eminence. In-vitro ethanol concentrations (5-25 mM), comparable to behaviorally relevant blood ethanol levels, induce a substantial inhibition of AVP release from the median eminence, whereas higher ethanol concentrations (greater than 50 mM) potentiate release. In vivo, ethanol, at a behaviorally relevant blood ethanol concentration (126 mg%), does not produce a significant difference in AVP content in brain although there is a consistent trend towards an increase in the hypothalamus and neurohypophysis. The results are considered in relation to the effects of ethanol on biogenic amine release and to memory impairments induced by low doses of acute ethanol exposure.