- Title
- Simulation of arterial chemoreceptor control of ventilation but not of arterial pressure by intracisternal infusion of substance P
- Creator
- Aggarwala, A. K.; Paxinos, G.; Gallagher, P. J.; White, Saxon William
- Relation
- 29th International Congress of Physiological Sciences: Antidromic vasodilatation and neurogenic inflammation: satellite symposium. Proceedings of the 29th International Congress of Physiological Sciences (Newcastle, N.S.W. 1983)p. 287-301
- Publisher
- Akadémiai Kiadó
- Resource Type
- conference paper
- Date
- 1984
- Description
- Afferent fibres from the arterial baro and chemoreceptors travel in the glossopharyngeal and vagus nerves to terminate mainly in the nucleus of the solitary tract (NST) (see Palkovitz and Zaborsky, 1977). Although the transmitter at the primary synapse of these special visceral afferents is unknown, immunofluorescent studies in the rat and cat have demonstrated substance P-like immunoreactivity (SP-I) in nerve fibres and cell bodies of the carotid body, the nodose and petrosal ganglia, in glossopharyngeal nerve fibres entering the brain stem, and in nerve terminals of the NST (Hokfelt et al. 1975; Hokfelt et al. 1977; Lundberg et al. 1978; Cuello and Kanazawa, 1978; Gamse et al. 1979; Lundberg et al. 1979; Cuello and McQueen, 1980; Jacobowitz and Helke, 1980; Gillis et al. 1980). That substance P (SP) may play a functional role in arterial chemoreceptor regulation of ventilation and the circulation is uncertain. Close arterial injection of SP into the cat carotid body causes a slight initial inhibition of arterial chemoreceptor afferent discharge, followed by a prolonged increase (McQueen, 1980). Local application of SP in the region of the NST in anaesthetized rats and cats evokes hypotension and bradycardia (Haeusler and Osterwalder, 1980), but the authors thought these cardiovascular data were consistent with a role for SP in arterial baroreflexes, rather than in arterial chemoreflexes. In this regard, a role for SP in arterial baroreceptor control has been denied (Furness et al. 1982), who found no change in the normal heart period-arterial pressure relationships in conscious guinea pigs following central and peripheral SP depletion induced by capsaicin. Observations of ventilation were not made in these studies. These data contrast with those of Bond et al. (1982), who found both arterial chemoreflex and baroreflex deficits in anaesthetized adult rats treated neonatally with capsaicin. Given the morphological evidence, in the present study the postulate that SP plays a role in arterial chemoreceptor control of cardiopulmonary function has been tested in conscious rabbits. Unanaesthetized animals were used because it is now well established that different anaesthetic agents can alter the sensitivity of different components of cardiopulmonary reflex arcs (e.g. Peiss and Manning, 1963; Korner et al. 1968). In the first part of the study, confirmation was sought for the presence of SP- I in the NST, petrosal ganglion and carotid body of the rabbit. Secondly, SP was infused briefly into the cisterna magna over the region of the obex. It was assumed that the exogenous SP would diffuse rapidly to receptor sites normally acted upon by endogenous SP, to produce a cardiopulmonary response, elements of which may resemble the known patterns of response evoked by the afferent inputs projecting to the NST when naturally stimulated. The final pattern would reflect the dominance of one input relative to another, e.g. a rise in ventilation would reflect the functional dominance of an increase in arterial chemoreceptor activity over an increase in arterial baroreceptor activity, which normally would cause an inhibition of ventilation. Finally, the mechanism of the SP induced hypotension observed by Haeusler and Osterwalder (1980) was examined in conscious rabbits pretreated with guanethidine sulphate to cause peripheral postganglionic sympathetic blockade and noradrenaline depletion.
- Subject
- arterial chemoreceptor; substance P; nucleus of the solitary tract; intracisternal infusion
- Identifier
- http://hdl.handle.net/1959.13/938902
- Identifier
- uon:12694
- Identifier
- ISBN:9630539969
- Language
- eng
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