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Biomedical subjects

N K MacLeod

Publications and source records attributed to N K MacLeod.

10 recordsLinked to original sources
PubMed1979

Responses of olfactory bulb neurones to the dipeptide carnosine.

Carnosine has been applied by microiontophoresis ot identified neurones in the olfactory bulb of the rat from solutions of different pH. Although mainly without effect when compared with conventional excitatory and inhibitory amino acids, the dipeptide tended to be depressive when ejected as a cation and excitant when ejected as an anion. The results obtained are not in favour of this substance being an excitatory transmitter in the primary olfactory pathway.

Amino Acids↗
PubMed1979

5,7-dihydroxytryptamine lesions of dorsal and median raphé nuclei and performance in the social interaction test of anxiety and in a home-cage aggression test.

Micro-injections of the neurotoxin 5,7-dihydroxytryptamine into the dorsal raphe nucleus produced a behavioural profile in the social interaction test of anxiety similar to that seen in rats treated chronically with benzodiazepines. Neurotoxin injections into the median raphé nucleus did not produce a profile significantly different from that of the controls. In the control rats and in the rats with lesions of the median raphé nucleus, ACTH1-24 (corticotrophin) significantly reduced active social interactions, whereas it was without effect on the rats with lesions of the dorsal raphé nucleus. In the home-cage intruder test, the median raphé-lesioned rats submitted less to the intruder and stood and jumped on him more often than did the controls. The dorsal raphé-lesioned rats showed significantly fewer interactions of all kinds, compared with control rats when an intruder was placed in their home cages.

5,7-Dihydroxytryptamine↗
PubMed1976

Field potentials in the olfactory bulb of the rainbow trout (Salmo gairdneri): evidence for a dendrodendritic inhibitory pathway.

Field potentials have been recorded from the olfactory bulb of the teleost fish, Salmo gairdneri. Stimulation of the olfactory nerve generates a complex wave pattern, which when recorded near the surface in the centre of the bulb consists of one positive and three negative components, P, N1, N2 and N3. The N1 has been attributed to depolarization of mitral cell dendrites, N2 to depolarization of the superficial dendrites of granules cells, and P to subsequent hyperpolarization of mitral cells. Possible origins of the N3 wave are discussed. Spikes from single units recorded in the mitral cell layer usually occur superimposed on the N1 wave, and single units recorded in the region of granule cells are usually found coincident with the trailling edge of the deep positive wave. With the exception of N3 the patterns of activity observed are very similar to previously published results obtained from other vertebrates. It is suggested that the dendrodendritic inhibitory pathway proposed for the mammalian olfactory bulb (Rall et al., 1966; Rall and Shepherd, 1968) is common to all vertebrates.

Animals↗
PubMed1976

Spontaneous activity of single neurons in the olfactory bulb of the rainbow trout (Salmo gairdneri) and its modulation by olfactory stimulation with amino acids.

Spontaneous action potentials recorded from 126 neurons in the olfactory bulb of Salmo gairdneri show a higher tendency towards bursting patterns of activity than those shown in previous reports about other fish. Granule cells and periglomerular cells are more likely to fire in bursts than mitral cells. Natural chemical stimulation of the olfactory mucosa with amino acid solutions produced a unique pattern of excitatory and inhibitory responses across all units. Chi-square values were calculated for stimulatory effectiveness between forty-five pairs of odours. L-serine and L-alanine consistently showed a high degree of similarity with several other odours. The converse was true for GABA and L-histidine, although this pair had a high chi-square value when mutually compared. Enantiomeric pairs of amino acids were often found to have opposite stimulatory effects on bulbar units. These results are discussed in relation to the possible properties and configurations of odorant receptor sites for amino acids in the fish olfactory mucosa.

Action Potentials↗
PubMed1976

Non-random distribution of cell types in the preoptic and anterior hypothalamic areas.

1. Single units were recorded extracellularly from the preoptic and anterior hypothalamic areas of male and female rats anaesthetized with urethane. 2. The effect of single shock stimulation of both the mediobasal hypothalamus and corticomedial amygdala upon unit activity was assessed for all cells. Neurones were designated either antidromically invaded, orthodromically excited or inhibited, or non-responsive. 3. The distribution of responses among recorded cells was analysed for two groups of neurones. In one group the intercell distance was less than 100 mum and in the second group the distance was more than 1 mm. 4. For widely separated cells the connexions with the corticomedial amygdala and mediobasal hypothalamus were distributed at random. 5. In the groups of cells clustered closely together a marked structuring of connexions was apparant. In particular, there was a significant correlation between orthodromic responses from the amygdala (P less than 0-05) and cells antidromically activated and orthodromically excited by stimulation of the mediobasal hypothalamus were frequently adjacent to one another (P less than 0-02. 6. A complimentary analysis demonstrated that cells in the ventral half of the recording zone received significantly more inhibitory inputs from both the mediobasal hypothalamus (P less than 0-001) and the corticomedial amygdala (P less than 0-02) than those situated more dorsally. 7. The data provide evidence for structuring and orderliness in hypothalamic connexions that is often not apparent from descriptions of electrophysiological experiments.

Amygdala↗