Effects of biogenic amines on central thermoresponsive neurones in the rabbit

SUMMARY1. The responses of fifty-five single units to changes in skin temperature were recorded in twenty-three guinea-pigs anaesthetized with urethane. Skin-temperature changes were induced by changing the temperature of the water-perfused support plate of the stereotaxic apparatus and that of the double-walled Perspex jacket that was put on the support plate.2. Thirty-three units were stereotaxically and histologically verified as being within a circumscribed area of the pontine dorsomedial reticular formation (subcoeruleus region). Twenty-one units were located in the surrounding areas, and one unit in the nucleus raphe magnus region.3. Twenty-seven of thirty-three recorded subcoeruleus units were specifically excited by cooling of the abdominal or leg skin, whereas only five units were non-thermoresponsive and one unit was warm-responsive. The cold-responsive units had peak activity at skin temperatures between 22 and 29 IC, in accordance with the maximum activity in cutaneous cold-receptors. 4. A markedly different distribution of units was found in the surrounding areas. Only four units were cold-responsive. Thirteen units were non-thermoresponsive, and four units were warm-responsive.5. The cold-responsive subcoeruleus units were situated in regions which are known to contain accumulations ofnoradrenergic cell bodies, and to project to hypothalamic neurones. Electrical stimulation of these regions is known to cause excitatory metabolic responses in unanaesthetized guinea-pigs. It is concluded that part of the cutaneous cold-afferents projects to hypothalamic thermointegrative neurones via noradrenergic pathways that ascend from these subcoeruleus regions.

“…This agrees with the function of noradrenalineasaninhibitorytransmitteronwarm-responsive hypothalamic neurones (Hori & Nakayama, 1973;Jell, 1974).…”

Section: Discussionsupporting

confidence: 87%

Responses of pontine units to skin‐temperature changes in the guinea‐pig

Hinckel

Schröder-Rosenstock

1981

“…Similar results have been obtained in the urethane-anaesthetized adult rat: 23 % by Jahns & Werner (1974) and 22*5 % by Boulant & Bignall (1973). Studies in other adult mammals also indicate more or less similar proportions of warm-units in the preoptic and anterior hypothalamic areas (Nakayama, Hammel, Hardy & Eisenman, 1963;Hardy, Hellon & Sutherland, 1964;Eisenman & Jackson, 1967;Guieu & Hardy, 1970; Hori & Nakayama, 1973;Boulant & Hardy, 1974). On the other hand, the percentage of cold-units in the new-born rat was very small, at most only 4 % in 21-24 day old rats, whereas those of adult rat have been described as being 13 % (Jahns & Werner, 1974) and 20% (Boulant & Bignall, 1973).…”

Section: Presented Insupporting

confidence: 74%

“…In adult mammals, slightly greater values for temperature coefficients of cold-units have been reported: -1 impulses/sec. 0C in the dog (Hardy et al 1964), -2-0 in the rabbit (Hori & Nakayama, 1973) and -1-68 (Boulant & Hardy, 1974) in the rabbit. Again, temperature coefficients of cold-units in the new-born rat are similar to those of units in the skink, which ranged between -0-26 and -0 7 impulses/sec.…”

Section: Presented Inmentioning

confidence: 97%

Hypothalamic thermo‐responsive neurones in the new‐born rat.

Hori¹,

Shinohara²

1979

SUMMARY1. Single unit activities were recorded from the neurones in the preoptic area and anterior hypothalamus of developing new-born rats (aged 1-24 days old) during thermal stimulation of the brain. During the first 2 weeks of life, about 80 % of these neurones had low spontaneous firing rates between 0.1 and 5 impulses/sec at 38 0C hypothalamic temperature (Thyp).2. Out of 640 units studied, 118 units increased the firing rate upon elevation of ThyP (warm-units) and fourteen showed the opposite type of response to temperature changes (cold-units),. Warm-units were founcli the rats of all the age span studied and cold-units were recorded in the rats more than 8 days old.3. Thermal coefficients of warm-units and cold-units varied between +0i11 and +2-47 and between -0.10 and -0*49 impulses/sec. 0C, respectively. Number of warm-units with higher rates of firing and greater thermal coefficients, comparable to those of warm-units in the adult, gradually increased with growth. The thermal responsiveness of warm-units, when expressed by Q10, are already high even in the immediate neonatal period. Their Q10 values were in the range between 2 and 38X5 (mean 6.4).4. Units responding to extrahypothalamic temperatures were only found in the rats more than 14 days old.5. All the six warm-units tested increased the firing rates following subcutaneous injections of capsaicin, while the majority of thermo-unresponsive units were not affected by this drug.6. It is suggested that thermo-responsive neurones in the preoptic area and anterior hypothalamus in the new-born rat have attained some degree of electrophysiological maturity, despite their slowly firing characteristics.

“…An accumulation of noradrenaline-containing cells has been demonstrated in the rat in the area of the reticular formation stimulated in the present study (Ungerstedt, 1971). Noradrenaline has been shown to act as an inhibitory transmitter on warm-responsive hypothalamic neurones (Hori & Nakayama, 1973;Jell, 1974). Microinjection of noradrenaline into an area located close to the sites of cell type c has previously been shown to produce thermoregulatory effects which greatly resemble those which followed stimulation of the reticular formation in the present study.…”

Section: Discussionmentioning

confidence: 89%

Thermoregulatory noradrenergic and serotonergic pathways to hypothalamic units

Brück

Hinckel

1980

SUMMARY1. In guinea-pigs hypothalamic single units were extracellularly tested for their response to thermal stimulation of the skin and to electrical stimulation of two different pontine areas, the nucleus raph6 magnus and the dorsomedial reticular formation. Furthermore, thermoregulatory control actions were measured during the stimulations.2. Electrical stimulation of those reticular formation areas containing noradrenaline cells caused an increase of oxygen uptake, electrical muscle activity and body temperature, while stimulation of the nucleus raphe magnus, known to contain serotonin cells, brought about inhibition or had no effect.3. The recorded units could be subdivided into three groups.Cell type a. Neurones on the boundary of preoptic and anterior hypothalamic regions which increased their firing rate when the skin was cooled and decreased it when the nucleus raphe magnus was stimulated. Cell type b. Neurones in the anterior hypothalamus which did not respond to brain-stem stimulation. Cell type c. More posterior neurones which increased their firing rate when the skin was warmed or when the nucleus raph6 magnus was stimulated and decreased their firing rate when the reticular formation was stimulated.4. Cell type a seems to represent interneurones which are connected to the ascending serotonergic thermoregulatory pathway. As for cell type c, it is inferred that it could represent interneurones which control the threshold for shivering and non-shivering thermogenesis.