Predictive genetic testing for Huntington's disease (HD) has revealed early cognitive deficits in asymptomatic gene carriers, such as altered working memory, executive function and impaired recognition memory. The perirhinal cortex processes aspects of recognition memory and the underlying mechanism is believed to be long-term depression (LTD) of excitatory neurotransmission, the converse of long-term potentiation (LTP). We have used the R6/1 mouse model of HD to assess synaptic plasticity in the perirhinal cortex. We report here a progressive derailment of both LTD and short-term plasticity at perirhinal synapses. Layer II/III neurones gradually lose their ability to support LTD, show early nuclear localization of mutant huntingtin and display a progressive loss of membrane integrity (depolarization and loss of cell capacitance) accompanied by a reduction in the expression of D1 and D2 dopamine receptors visualized in layer I of the perirhinal cortex. Importantly, abnormalities in both short-term and long-term plasticity can be reversed by the introduction of a D2 dopamine receptor agonist (Quinpirole), suggesting that alterations in dopaminergic signalling may underlie early cognitive dysfunction in HD.

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We report a change in the vascularisation of the adipose depots surrounding the popliteal lymph node that has, and the contralateral node that has not, been exposed to a simulated immune challenge. The percentage of the depot that consists of vessels, as measured by image analysis, decreases over a period of 2 d after immune stimulus, then increases in a biphasic manner over the next 2-3 wk. By 1 mo after the stimulus, the vascularisation has returned to baseline values. The adipose tissue surrounding both the stimulated and the unstimulated lymph nodes shows a similar pattern, but the unstimulated depot lags by 3-6 d in reaching its maximum vascularisation. These data support the hypothesis that perinodal adipose tissue is involved in peripheral immune responses.

Competition between unmated females for males was observed in the smooth newt, T. vulgaris, during the early part of the breeding season. Females interfered at the spermatophore‐transfer stage of courtship, preventing a rival female from picking up the sperm mass. Interference often resulted in the rival female abandoning the courtship encounter. In many of the encounters (70%), the interfering female was inseminated. However, interference between females was not observed after the commencement of ovulation. By contrast, the incidence of sexual interference between males was low during the preovulatory period and increased significantly post‐ovulation. Sexual interference in newts and salamanders has previously only been observed between males. During the greater part of the breeding season, when females are ovipositing, eggs are the limiting resource and males compete for access to receptive females. However, this study suggests that early in the breeding season, prior to commencement of ovulation, the limiting resource may temporarily be sperm, due to the physiological constraint of spermatophore production. This may lead to female competition for mates.

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